The aim of the study was to find which linear measurements, field and volume coefficients correlate the best with real volume of the spleen and can be further used for identification of splenomegaly.3. Data were analyzed with use of Pearson correlation and χ2 test with statistical significance at p < 0.05.Abdominal computed tomography (CT) examinations of 264 patients were retrospectively analyzed in terms of maximal length, maximal thickness, hilum thickness, maximal height, vertical height and estimated height. Spleen volume was manually measured in Vitrea software. Two- and three-dimensional coefficients were calculated through proper mathematical formulas from linear measurements. Splenomegaly cut-off: 314.5 cmr = 0.804; p < 0.05). Among two-dimensional indexes, multiplication product of maximal length and vertical height reached the highest level of correlation with spleen volume  and had the highest sensitivity and specificity  for splenomegaly detection (threshold 115 cm2). In case of three-dimensional ones, the coefficient calculated from maximal length, vertical height and hilum thickness established the strongest link with spleen volume .For single measurements, the correlation with real spleen volume was the strongest for maximal height , with the cut-off 115 cm Splenomegaly is a common clinical pathological finding of various aetiologies, including congestive, excessive antigenic stimulation, destruction of abnormal blood cells and neoplastic infiltration. It may be detected in symptomatic and coincidentally, in asymptomatic patients. Thus, appropriate evaluation of the spleen size seems to be necessary in order to initiate a diagnostic process, take proper therapeutic decisions and follow treatment effect in definite cases , 2.Primarily, the clinical diagnosis of splenomegaly is defined as the organ palpable below the costal margin during physical examination . HoweverThere have been multiple approaches for a precise evaluation of spleen size basing on CT examination. To this end, individual linear measurements, multidimensional coefficients as well as volume measurements have been applied. These include a popular, but rather obsolete formula called splenic index—multiplication product of maximal length, estimated height and maximal thickness of the spleen with the upper normality limit for splenomegaly set at 480 .Clinical routine requires simultaneously reliable and practical solutions. At present, clear and unequivocal guidelines for splenomegaly assessment in CT are lacking. Therefore, the aim of this study was to find which linear measurements and two-dimensional and three-dimensional coefficients correlate the best with real volume of the spleen and can be further used for determination of splenomegaly.n = 128) of the patients were female and 51.5% (n = 136) male. Patients included into the study were referred to the Department of Diagnostic Imaging to undergo abdominal CT due to various clinical symptoms related to the abdominal region. The exclusion criteria were spleen injury, multi-organ injury, spleen focal lesion, previous splenectomy and any condition that would affect the position of the spleen.We included into the study and retrospectively analyzed 264 abdominal CT examinations, which were carried out at the Department of Diagnostic Imaging of the University Hospital  in Cracow in the period between September and December 2016. Mean age of examined patients was 58.8 ± 15.5 years, age ranged between 16 and 91 years. 48.5% , in an abdominal protocol, scan parameters: 120 kV, 385 mAs; rotation time 500 ms; slice thickness 2.0 mm, interval 1.6 mm, to acquire axial images of the abdominal region. Coronal sections were obtained using multiplanar reconstructions (iterative reconstruction method), parameters: slice thickness 2.0 mm, interval 2.0 mm.Vspl) were assessed with the use of Vitrea Software 6.7.1 . All linear measurements were done in millimeters, while volume of the spleen was calculated in cm3. All values of measurements were presented as the value ± standard deviation.Linear measurements and volume of the spleen parenchyma (Lmax)—the longest dimension between poles of the spleen in this section,maximal length (max)—the widest dimension perpendicular to the long axis of the spleen,maximal thickness (Thhilum)—dimension measured in central part of the hilum perpendicularly to the long axis of the spleen.hilum thickness —the longest dimension between poles of the spleen in this section,maximal height (Hvert)—the longest vertical dimension between cranial and caudal borders of the spleen.vertical height  was assessed as the number of axial scans with the spleen visible multiplied by the slice thickness.Additionally, estimated height of the spleen  and three-dimensional (3D) coefficients were calculated as the product of multiplication of respectively two  or three various dimensions (length × thickness × height). In our study, 11 two-dimensional and 6 three-dimensional coefficients were counted.The real spleen volume was measured manually with the Volume Measurement Tool by defining the frontiers of the spleen on the surface of fibrous capsule (in a soft tissue window) in the coronal section. Subsequently, the volume was calculated by the software and three-dimensional reconstruction of the organ was obtained Fig. .Fig. 3ThAll measurements of the spleen were evaluated by two independent examiners simultaneously and the mean of two separate measurements of the identical parameter was classified as the final value. All significant discrepancies in measurements between examiners were analyzed and assessed one more time in the presence of a third examiner.p < 0.05. Linear Pearson’s correlation was used to assess the strength of correlation between dimensions along with coefficients and volume of the spleen.Statistical analysis was performed in Statistica 12.5 software . Statistical significance was set at 3 as volumetric threshold of splenomegaly, according to Prassopoulos et al. study [Cut-off points for detection of splenomegaly for linear measurements along with two-dimensional and three-dimensional coefficients were calculated in each case from equations of linear regression calculated by the software. Value of 314.5 cml. study , was subn = 35) of patients in the study had splenomegaly according to previously mentioned volumetric criterion. Reasons of spleen enlargement in our study were liver cirrhosis, Hodgkin lymphoma, chronic lymphoid leukemia (CLL), hemolytic anemia and acquired immune deficiency syndrome (AIDS). Mean volume of the spleen were 178.1 ± 64.2 and 481.4 ± 242.0 cm3 in groups without and with splenomegaly, respectively. Any statistically significant differences in terms of age and gender between groups with or without splenomegaly were not detected . Splenomegaly threshold for this parameter was 12 cm (equation of linear regression: Vspl = 6.393 × Hmax + 444.129). Sensitivity, specificity, PPV and NPV values were 71.4, 91.7, 56.8 and 95.5%.The strongest correlation with splenic volume was detected for maximal height . Calculated splenomegaly cut-off was 10.5 cm . This dimension improved values of sensitivity, specificity, PPV and NPV: 82.9, 91.7, 60.4 and 97.2%, respectively.Similar strength of correlation was observed in case of vertical height  − 92.464). Calculated splenomegaly threshold: 116 cm2. Approximation to 115 cm2 did not have any impact on qualitative parameters of effectiveness of the coefficient. Sensitivity, specificity, PPV and NPV values for 115 and 116 cm2 were 94.3, 93.0, 67.3 and 99.1%, respectively. Rounding up to 120 cm2 caused a slight decline in the value of sensitivity (91.4%) and NPV (98.6%) still remaining at a high level and elevation of specificity (94.3%) and PPV (71.1%).Multiplication product of maximal length and vertical height correlated the strongest with volume of the spleen  + 18.889). The cut-off point for splenomegaly was 492 cm3. Values of sensitivity, specificity, PPV and NPV were equal for 492 cm3 and approximated 490 cm3: 82.9%, 95.6%, 74.4% and 97.3%, respectively. Rounding up to 500 cm3 had a negative impact on specificity (77.1%) and NPV (96.5%), but slightly increased the level of specificity (96.5%) and PPV (77.1%).The strongest correlation with the spleen volume was discovered for a coefficient calculated by multiplication of maximal length, vertical height and hilum thickness  + 18.889). Additionally, for the threshold at the level of 739 cm3, it had improved values of specificity (96.1%) and PPV (76.3%) along with equal sensitivity and NPV to the above-mentioned coefficient. Nonetheless, approximation to 740 cm3 alters sensitivity, specificity, PPV and NPV to values 80%, 96.5%, 77.8% and 96.9%, respectively.A coefficient counted by multiplication of maximal length, vertical height and maximal thickness had a fine correlation with the spleen volume as well  + 56.023), compared to other three-dimensional coefficients. The calculated cut-off point for that coefficient was 1010 cm3. Sensitivity, specificity, PPV and NPV were 62.9, 93.9, 61.1 and 94.3%, respectively.The correlation of splenic index  with volume of the spleen was rather poor . Moreover, the coefficient calculated from maximal length, vertical height and maximal thickness had a fine correlation with the spleen volume as well . Thus, they can be valuable for the assessment of changes in the spleen volume in cases in which this parameter is helpful for stating the diagnosis , or monitoring the clinical condition, e.g., after spleen embolization, during the treatment of hemolytic anemia, myeloproliferative disorders, lymphoproliferative syndromes, acute leukemia, storage disorders (like Gaucher’s or Neumann–Pick’s disease) [r = 0.846; p < 0.05). Lackner et al. introduced the term of splenic index defined as a multiplication product of maximal length, estimated height and maximal thickness of the spleen. Comparing its value set with the use of computed tomography with the one assessed during the autopsy, it was observed that CT have a tendency to underestimate and overestimate this index. As for its limitations, a study was carried out on a relatively small group (118 patients) in comparison to ours (264 patients). Additionally, Lackner et al. study was carried out in the times when CT quality was rather poor in comparison to the technology at present, which could have affected the accuracy of measurements. However, age, race and gender differences in spleen volume were not taken into account in both studies [3, respectively). Nevertheless, the cut-off point for the splenic index calculated in our study (1010 cm3) differs considerably from the one suggested by Lackner et al., which makes their coefficient totally unreliable to use.Among all coefficients, three-dimensional ones seem to be the best means of spleen size evaluation, since they represent the highest level of correlation with real volume of the spleen. The highest correlation coefficient was detected for the multiplication product of maximal length, vertical height and hilum thickness of the spleen (disease) . In cont studies . Since tr = 0.923; p < 0.05). Moreover, it happened to present the highest sensitivity and specificity , which makes it a great screening tool for radiologists for the quick evaluation of the spleen. With a threshold indicating splenomegaly set at the level of 115 cm2, it would help to give a hint for clinicians if they should take a closer look on the spleen and supposedly pay more attention to this organ, and generally, conditions connected with spleen enlargement in terms of the future diagnostic process. Since this coefficient is a combination of measurements done in two sections—axial and coronal, it lowers the chance to overlook the spleen enlargement, in comparison to two-dimensional coefficients based on dimensions measured only in one section. The splenomegaly threshold can be rounded up to 120 cm2 (to be easily memorized). Despite still high level of specificity (94.3%), this approximation leads to a decline in sensitivity (91.4%) and consequently, it needs to be considered if such changes are worth establishing.The two-dimensional coefficient, set as a result of multiplying maximal length and vertical height, represented a high level of correlation with the real volume of the spleen  of the spleen represented the strongest correlation with the volume. This measurement is consistent with the so-called cephalocaudal spleen height, which is used in clinical practice for a quick assessment of the spleen size in CT [r = 0.756 and r = 0.585, respectively) [Considering the linear measurements, maximal height (ze in CT . Bezerractively) . Maximalctively) . It needThere are also more complex methods of defining splenomegaly, such as the relationship of the spleen to the left lobe of the liver (ultrasound) , or to tThe spleen volume is directly linked with the weight of the organ. It has been known for a long time that spleen weight increases proportionally to the body weight, declines with the age and is generally slightly smaller among women . Thus, fIt needs to be remembered that the definition of splenomegaly is highly individual and its diagnosis should always be tightly bound with a clinical condition of the patient, rather than treating it as an isolated radiologic diagnosis. However, the coefficients and thresholds can play a vital role in catching the change in spleen size at an early stage. Despite geometrical limitations , all coefficients represented a high level of correlation with the real volume of the spleen and can be used as a supportive tool in the daily clinical practice.three-dimensional coefficient calculated as:or two-dimensional coefficient, resulting from equation:Due to the poor accuracy of splenic index, it should be replaced with:


The accessory spleen is a congenital defect characterized by a separated ectopic splenic parenchyma. The size is rarely more than 4 cm. The preoperative diagnosis is prohibitive preoperatively. The aims of the present manuscript were to present the case of a patient with a rare oversize accessory spleen and a review of the literature.A 15-year-old boy was admitted to the emergency department following blunt abdominal trauma.The computed tomographic scan showed a traumatic rupture of the spleen and a 7-cm mass at the left side of the retroperitoneal space. Conservative treatment started and aborted after 4 h due to the onset of haemodynamic instability. Splenectomy was performed. An accessory spleen was discovered. A second large mass in the retroperitoneum was diagnosed as a second large accessory spleen that was also left in place. The postoperative course was uneventful, and the patient was discharged on the 7th postoperative day. Seven months later, the CT scan showed viability of both accessory spleens.An accessory spleen can be variously located and the retroperitoneal position is extremely uncommon. Preoperative diagnosis is still difficult, especially in emergency and as in our case, the literature shows the difficulty of reaching a diagnosis before surgery. The main misdiagnosis is neoplastic disease and for this reason accessory spleen can be wrongly removed.An undiagnosed pre or intra operative retroperitoneal mass, closely to the spleen, have to be managed carefully. The diagnosis of accessory spleen needs to be ever considered as if found, represents a great possibility to conduct a normal life after splenectomy (of main spleen) for trauma. The spleen appears approximately at the sixth week of embryologic life as a localized proliferation of the coelomic epithelium overlying the dorsal pancreatic endoderm. The proliferating cells invade the underlying angiogenic mesenchyme; as a result, it becomes condensed and vascularized in several adjoining areas that fuse together determining the formation of a lobulated spleen , 2. SubsThe spleen is localized between the 9th and 11th left ribs in abdominal cavity, between the gastric bottom and the left hemidiaphragm. With a weight of approximately 200 g, it represents the largest lymphoid organ in the body . It is fDuring its growth, the spleen can develop anomalies such as complete agenesis, multiple spleens or polysplenia, accessories spleens, isolated small additional splenunculi and persistent lobulation.The accessory spleen is a congenital defect, with a separated ectopic splenic parenchyma due to an incomplete fusion of splenic masses during embryonic growth arising from the dorsal mesogastrium .The aims of the present manuscript were to present a case of a patient with a rare oversized accessory spleen and a complete update of the literature concerning this rare condition.In June 2017, a 15-year-old boy was admitted to the emergency department following blunt abdominal trauma after being hit by a car while he was observing a car race.The patient was intubated and was haemodynamically stable ; therefore, laboratory tests and CT-scan were performed.The computed tomographic scan of the thorax and abdomen showed bilateral pleural effusions with rib fractures and a large haemoperitoneum associated with a traumatic rupture of the spleen with multiple injuries  and a 7Haemoglobin decreased from 14.4 to 8.9 g/L during hospitalization with four hours of conservative treatment, with appearance of haemodynamic instability that was considered an indication for surgery.An incision was made on the midline. The abdomen was packed and explored. The operation began with clearance of the haemoperitoneum. The spleen appeared with multiple longitudinal lesions in the visceral aspect. It was gently grasped and displaced medially towards the incision. The avascular peritoneal attachments and ligaments are incised with by electrocautery, followed by dissection of the splenogastric ligament and ligation of the short gastric vessels near the spleen to avoid injury or late necrosis of the gastric wall. The splenorenal, splenocolic and splenophrenic ligaments were divided. To avoid pancreatic injuries, dissection was carried out in close proximity to the hilum of the spleen, where the splenic artery and veins were identified, carefully dissected, doubly ligated and fixed with suture ligatures. After removal of the spleen, haemostasis was obtained and confirmed in a systematic fashion through careful inspection of the left subphrenic area, the greater curvature of the stomach and the short gastric vessel area, as well as the splenic hilum. Inspection of these areas showed an accessory spleen connected to the omentum by a vascular pedicle that was moved to the splenic fossa and fixed to the diaphragmatic peritoneum by prolene stitches to protect it from future traumatic injuries  Fig. 2)2). A cloThe postoperative course was uneventful, and the patient was discharged on the 7th postoperative day. He was followed up for 7 months, during which he was well with no complications. A CT scan performed a couple of months after the surgical procedure showed the viability of the small spleen close to diaphragm. Radiological examination revealed the mass in the retroperitoneal space confirming a second accessory spleen Fig. .Fig. 3CTNeisseria meningitidis or Streptococcus pneumoniae [The spleen is an important organ for the normal activity of the immune system. In fact, in case of asplenia, the patient is subject to an increased risk of sepsis or infections that may be caused by encapsulated bacteria such as eumoniae . FurtherAsplenia, polysplenia or multiple spleens, hyposplenia, accessory splenic nodule and persistent lobulation represent the congenital malformations of the spleen. Other rare congenital anomalies are reported in the literature, but they are not relevant to our study. By contrast, splenosis is an acquired alteration.Asplenia is a very rare condition defined by the complete absence of the spleen. This condition is also known as Ivemark’s syndrome .Polysplenia, or multiple spleens, is due to the absence of fusion of the primordial germs of the spleen. Therefore, between 1 and 6 small spleens are present in the abdominal cavity with dimensions between 1 cm and 6 cm; however, the total volume does not exceed the volume of a normal spleen . Often tHyposplenia can be congenital, with a small spleen that can be the cause of immunodeficiencies in children . HyposplThe lobulation of the spleen is an alteration of the spleen’s shape that has no pathological value .Splenosis is defined as auto-transplantation of splenic tissue in a heterotopic location that primarily develops as a consequence of splenic trauma or surgery .An accessory spleen is defined as ectopic splenic tissue that develops due to the failure of cell fusion during embryonic development while migrating from the midline to the left upper quadrant , 16. TheAccessory spleen can be present in 16% of the population, and they are found in 10–30% at autopsy . AccessoThese accessories spleens are often asymptomatic but may present as an abdominal mass connected to complications such as torsion, haemorrhage, spontaneous rupture or cyst formation. They are diagnosed during radiological examinations for other diseases. Their diagnosis becomes mandatory only in cases of haematological disorders . In factAccessory spleens look like normal spleens also in terms of immunologic functions. In haematologic disorders, when splenectomy is the treatment of choice, accessory spleens have to be located and removed because they will become hyperplastic and cause recurrence of the disease.Accessories spleens may demonstrate compensatory hypertrophy and can grow to 3–5 cm after removal of the principal spleen .Preoperative diagnosis of the accessory spleen is difficult, especially in emergencies. CT scans show a well-margined mass, similar to the splenic parenchyma on the contrast phase. Magnetic imaging can also be used to evaluate tissue aspects and the vascular pedicle of the accessory spleen. Only nuclear medicine imaging can confirm the diagnosis with scintigraphy performed with 99mTC-labelled colloids or TC-99 m heat damaged red blood cells because the colloid labelled with TC 99 m is taken from the reticulum-endothelium and makes visible the spleen, liver and bone marrow; however, it is necessary to suspect the diagnosis of accessory spleen for this procedure . TherefoTo perform the review of the literature, relevant articles in English were extensively searched from the MEDLINE (PubMed) database. The period of research was between 1999 and 2018. The date of the last search was July 10, 2018. The keywords used for the search were “spleen” “accessory spleen”, “retroperitoneal”, “retroperitoneal mass”, “retroperitoneal tumor”, “retroperitoneal spleen” “trauma”, “right”, and “omentum”. These words were used individually or with the Boolean operator “AND”. A total of 205 articles were analysed between 1999 at 2018. Of these 205 articles, 57 manuscripts  were excluded because they did not report cases of accessory spleen, 43  were duplicates manuscripts, 34 manuscripts  analysed cases of intra-organ spleens, 31 articles 15, 1%) showed cases of splenosis and 23 manuscripts  were not written in English  for trauma.


Children between the ages of 9 and 12 – commonly called tweens – are one of the fastest growing audiences for YouTube content. The current study explores how tweens are watching YouTube and the nature of their parasocial relationships and wishful identification with their favorite YouTube personalities. Results show that tweens identified gender-congruent YouTubers as their favorite. Moreover, tweens perceived male and female YouTubers to have different attributes. For instance, male YouTubers were rated as more violent than female YouTubers, and female YouTubers were rated as more attractive and popular than male YouTubers. Gender also played a role in attachment patterns. Tween boys’ wishful identification was predicted by YouTubers who were violent and funny and their parasocial relationships were predicted by YouTubers who were funny, successful, and attractive. Meanwhile, tween girls’ wishful identification was predicted by YouTubers’ who were funny, and their parasocial relationships were predicted by YouTubers’ who were funny and popular. Results are discussed in terms of gender socialization theory. YouTube has over 2 billion users per month , and a bYouTube personalities, or “YouTubers,” have emerged as a new kind of celebrity, accumulating millions of fans and earning tens of millions of dollars annually. Compared to traditional media wherein tweens merely view content, YouTube allows tweens to interact with their favorite YouTuber by commenting on videos and sometimes directly communicating with the YouTuber. Tweens can also engage in various ways when they are not using the YouTube platform. For instance, they can purchase YouTubers’ merchandise, see them at sold-out arenas, watch them on television events such as the Nickelodeon Kids’ Choice Awards, or follow them across other social media platforms. With ample opportunity to engage with YouTubers, it stands to reason that tweens are forming attachments to these new celebrities.Previous research on children’s character attachments has focused on the psychological mechanisms of wishful identification (WI) and parasocial relationships (PSR) with mass media characters. This body of work reveals that (1) children can form these attachments; (2) there are gender differences in how attachments are formed; and (3) WI and PSR function as mediators between media exposure and effects. Given the differing levels of interactivity between mass media and YouTube, new patterns of WI and PSR may be forming between children and their favorite YouTuber. The purpose of this study is to understand more about tweens’ use of YouTube and the nature of WI and PSRs that tweens are forming with their favorite YouTubers.favorite YouTubers, Research on tweens’ viewing relationships with YouTubers is beginning to emerge. One study found that 40% of tweens reported watching YouTube specifically to view YouTubers . In a survey of United States tweens, 34% could name a favorite YouTube show, channel, or star . When twOne explanation for the popularity of YouTubers is that the time tweens are spending on YouTube is increasing. Recent data shows a significant increase in the amount of time American tweens spend watching YouTube, jumping from 25 min a day in 2015, to 56 min a day in 2019 . Data frAnother reason tween viewership has seen an increase is due to ease of access. Over half (52%) of American tweens have their own tablet, 41% have their own smart phone, and 23% have their own laptop computer . SimilarAlthough data have indicated that YouTube is extremely popular among tweens, when compared to what we know about youth television viewing habits, we know very little about the specific contexts of tween’s YouTube viewing. For example, we do not what time of day they are watching, or if they watch more on weekdays than on weekends. We also do not know if tweens typically co-view with friends or family or watch alone. Over half (61%) of American parents with children under eleven reported that their child has encountered YouTube content that was “not suitable for children” . One way1:RQIn what contexts do tweens watch YouTube?Evidence has begun to emerge that tweens are absorbing information and learning new ideas and behaviors from YouTube videos. One way in which tweens may consider themselves similar to YouTubers is through gender identity. In line with social cognitive theory, gender schema theory posits that children watch members of their own gender to learn how to behave as a male or female . More spPrevious research has established that child gender plays a role in attachments to television and film characters. In one early study, Past research has focused on children’s attachments to media characters featured in traditional mass media outlets such as television and film. To date no one has studied how children form attachments to interactive media celebrities like YouTubers. There is reason to speculate that there may be differences between tweens’ favorite mass media characters and their favorite YouTubers. For instance, Another difference that may impact tweens’ choices in favorite characters is that there remains an overrepresentation of male characters on television and film see , which m1:HTweens will select gender-congruent YouTubers as their favorite more often than they will select YouTubers of a different gender.Research has also found that boys and girls perceive different qualities in their favorite male and female characters. For instance, preschool girls were found to identify more with characters who were sassy whereas boys’ identified based on the strength of the character . Hoffner2:RQHow does gender of the YouTuber influence tweens’ perceptions of their attributes?wishful identification. Wishful identification (WI) is the psychological desire to be like a media personality  is conceptually related to but distinct from WI. Parasocial interaction involves the emotions, thoughts, and actions that a viewer experiences during media exposure that are geared toward a specific performer or character . When exPSRs are a normal occurrence in traditional media environments and are experienced both by adults and by children . Much livia social media platforms. Researchers have recently started to explore PSRs in new media environments, such as 4:HTweens’ parasocial relationships will be positively related to time spent on YouTube.In children, PSRs have been positively related to the social realism of television characters . A human5:HTweens’ parasocial relationships with YouTubers will be positively related to perceived similarity to self.Finally, results from a handful of studies suggest that different character attributes predict PSRs for boys and girls. 4a:RQHow do the perceived characteristics of YouTubers relate to tween boys’ parasocial relationships with their favorite YouTuber?4b:RQHow do the perceived characteristics of YouTubers relate to tween girls’ parasocial relationships with their favorite YouTuber?Although YouTube viewership can be similar to mass media viewership, there are distinct differences in how the platform is used, which can alter the viewing experience for audience members. For instance, YouTube viewers can interact with content creators in comment sections on the platform as well as across other social media platforms. In fact, it is not uncommon that a YouTuber will participate in the conversations in his or her comments section. Additionally, YouTube has direct messaging abilities that allow viewers and content creators to privately interact with one another. Finally, not only do YouTubers and viewers interact with one another, but viewers also interact with other viewers, fostering a palpable sense of community on a YouTuber’s page . Given t5:RQAre parasocial relationships related to following a YouTuber on other social media platforms?Compared to traditional mass media, one of the affordances of YouTube is the ability to interact with the content producer. A viewer can leave comments on a YouTuber’s videos and send private messages to a YouTuber. It is not uncommon to receive a response from a celebrity on social media . Conceiv6:HParasocial relationships among tweens will be positively related to receiving responses from the YouTuber.N = 161) was 52% female and 48% male, with an average age of 10.78 years (SD = 0.822). Over half (59%) of participants indicated that they were white, 23% were of mixed race, 6% were Asian, 5% were Hispanic or Latino, 4% were Black, and 3% of the participants marked “Other” as their race.A total of 161 children, aged 9 through 12 years old, participated in the study. Participants were recruited in a large, metropolitan area in the southern United States through local school districts, local public libraries, and events at a university. Participants received a $5 debit gift card. The sample  of children at a time. A researcher read each survey item aloud as participants marked their answers.end day. An example item from the scale asked, “On the average weekday how much total time do you spend on YouTube after school but before dinner?” Response options included, 0 (No time), 1 (1–30 min), 2 (31–60 min), 3 (1–11/2 h), 4 (11/2–2 h), 5 (2–21/2 h), 6 (21/2–3 h), and 7 (3+ h). Each participant received a score indicating his or her average time spent on YouTube during the weekday , weekend days , and full week . Higher scores indicated more time spent.In order to understand the nature of YouTube use, participants were asked about the time they spend on YouTube. Participants reported how much time was spent on YouTube during different parts of an average weekday and an average weekParticipants were asked which device(s) they use to watch YouTube and were directed to mark all answers that apply. Answer options included (1) Laptop/Computer, (2) Cell phone, (3) Tablet, (4) Gaming console, (5) Other.Three items were used to assess how often tweens watch YouTube with other people. Participants were asked to identify how often they watched YouTube (1) alone, (2) with their parents, and (3) with their friends. Participants responded using a 5-point Likert-type scale ranging from 1 (never) to 5 (every time).Participants identified their favorite YouTube personality by writing his or her name and/or the YouTube channel name. Participants also provided the gender, approximate age, and racial demographics of the YouTuber. It should be noted that once participants identified their favorite YouTuber they were asked to write the name of the YouTuber on each of the remaining pages of the survey. Subsequently every time participants moved to a new page in the survey, the researchers could remind them to review their favorite YouTuber and answer the questions accordingly.M = 3.83, SD = 0.81). Higher scores indicated a stronger PSR with the YouTuber.A 5-item scale was used to measure the intensity of PSRs .A 5-item scale was used to measure wishful identification .To test if cross-platform exposure influenced attachment to their favorite YouTubers, participants were asked to indicate whether they followed their favorite YouTuber on Instagram, Facebook, Twitter, Snapchat and Musical.ly (now known as TikTok). A sum score was computed, ranging from 0 to 4, with higher scores indicating following the YouTuber on more social media platforms , successful , attractive , funny , popular , and violent .To measure the perceived character attributes of the chosen YouTube personality, a set of six scales were adapted from M = 16.62, SD = 4.84). For instance, items included the stem “My favorite YouTuber…” (1) “doesn’t think like me” to (7) “thinks like me” and (1) “doesn’t behave like me” to (7) “behaves like me.”Perceived similarity to the participant’s favorite YouTube personality was measured using the attitude similarity subscale of the Perceived Homophily Measure  of the tweens in this study reported watching YouTube. Only three participants reported not watching YouTube. Those who did watched on a variety of devices. Almost three-quarters (73%) of the sample accessed YouTube on a tablet. Watching on a cell phone was almost as popular, with 70% of the sample reporting doing so. And a majority of tweens (65%) reported watching on a laptop or computer. It was less common to watch YouTube through a videogame console, but even so, almost one-third (28%) of the sample reported watching YouTube this way.M = 2.09, SD = 1.66) than on the average weekday . The most popular time to watch YouTube was in the evening “after dinner but before bed” with a majority (74.5%) of tweens reporting spending some time on YouTube during this time period both during the week and on the weekends. Interestingly, when asked if they watch YouTube “after bed when they are supposed to be asleep,” roughly two out of five tweens admitted to spending at least some time watching YouTube when they were supposed to be sleeping during the weeknights (36.3%), and weekend nights (40.8%).In order to assess how much time was spent on YouTube each week, tweens were asked two sets of questions about time spent on the average weekday and on the average weekend day. On average, tweens spent about 15–30 min watching YouTube every day throughout the week. They reported spending significantly more time watching YouTube on the average weekend day  of the participants reported watching YouTube by themselves “almost every time” and 21% reported watching alone “every time” they watched. It was also common to watch with friends, with three out of five participants (58%) in the sample reporting doing so “sometimes.” It was extremely rare for participants to report watching YouTube with parents. In fact, a majority (82%) of tweens in this sample reported co-viewing YouTube with their parents “never” or “almost never.” Only 2 individuals (1%) reported watching YouTube with a parent “every time.”An overwhelming majority of participants (91.9%) reported having a favorite YouTuber. Only 13 out of 161 participants said they did not have a favorite YouTuber, and thus were excluded from further analysis. Participants identified a total of 98 unique YouTubers as their favorite, demonstrating the vast array of YouTubers who attract tweens. The most popular YouTubers listed were DanTDM (3.7%), Ali-A (3.1%), and The Odd 1s Out (3.1%). A full list of all YouTubers reported is available in There was little diversity in terms of the age and race of the YouTubers. Participants identified a majority (87%) of the YouTubers as over the age of 18, with only 6% listed as 10 to 12-years-old, 5% between 13 and 15-years old, and only 1% between 16 and 18-years old. A majority (65%) of YouTubers listed were identified as white, 10% were identified as mixed race, 6% as Black or African American, 4% as Asian, 3% as Hispanic or LatinX, and 2% were identified as “other.”2 = 63.44, p < 0.001. In support of Hypothesis 1, almost all tween boys (97.2%) selected a same-gender YouTuber as their favorite and a majority of tween girls (65.3%) selected a female YouTuber as their favorite ; t.In total 96 male and 51 female YouTubers were chosen as favorites. The first hypothesis proposed that male participants would be more likely to choose male YouTubers, and female participants more likely to choose female YouTubers. A chi-square analysis on the frequency of male and female YouTubers by gender of the participants was significant, χrite see . Althougt-tests were conducted to test the differences. Female YouTubers were rated as more attractive  than male YouTubers ; t and as more popular  compared to male YouTubers ; . Female YouTubers tended to be perceived as more successful  compared to male YouTubers ; . Meanwhile, male YouTubers were rated as more violent  than their female counterparts ; . There were no differences between males and females on their rated intelligence, or humor.The second research question asked how tweens perceived different characteristics between male and female YouTubers. Independent-samples SD = 0.90), indicating that tweens did experience WI with their favorite YouTuber. In all, half of the participants had scores at or above the mean, and about one-third (30%) of participants had WI scores at or above 4, signaling that many tweens had strong WI with their favorite YouTuber.Tweens could score from 1 to 5 on the WI index. The mean score was 3.6 (p < 0.01) such that more time spent on YouTube was related to higher WI scores  were entered into Block 1. These variables did not predict WI. Time spent on YouTube was entered into Block 2. This block was significant . Thus, H3 was supported.The third hypothesis predicted that perceived similarity between the participant and YouTuber would be positively related to tweens’ WI. A hierarchical linear regression was run in which participant demographics and time spent on YouTube were controlled in Blocks 1 and 2, respectively see . Block 3p < 0.05) and intelligent . To test if child gender moderated any of these relationships, interaction terms were entered into the Block 5 of the model. Results show that child gender significantly moderated the relationship between YouTuber violence and WI . Specifically, boys’ WI increased as YouTubers violence increased, whereas girls’ WI decreased as YouTubers violence increased , indicating a tendency for tweens to experience a fairly strong relationship with their favorite YouTuber. In fact, a majority (81.6%) of the sample scored above a 3, and over half (53.1%) of the sample scored over a 4 on the scale, indicating many of the participants had strong PSRs with their favorite YouTuber.Tweens could have a PSR score ranging between 1 and 5. The mean of the PSR score was 3.83 (p < 0.001). Thus, hypothesis 4 was supported.The fourth hypothesis predicted that PSRs among tweens would be positively related to time spent on YouTube. A hierarchical linear regression was conducted to test this hypothesis see . The firp < 0.01)  see . Thus, hp < 0.01). Interaction terms were entered into the final block of the analysis. Results show that child gender significantly moderated the relationship between YouTuber successfulness and PSR . Specifically, boys’ PSR increased for more successful YouTubers (see p = 0.05), and between YouTuber popularity and PSR . Tween boys tended to have stronger PSR for attractive YouTubers  of the tweens reported following their favorite YouTuber on at least one other social media platform. The most popular social media platform used to follow a YouTuber was Instagram (31.3%), followed by SnapChat (20.4%), Musical.ly (12.2%), Twitter (10.2%), and Facebook (1.4%). Research question 5 asked if following a YouTuber across other social media platforms is related to PSRs. Another hierarchical linear regression was conducted, which controlled for the child demographics and time spent on YouTube. The third block of the analysis included the total number of social media platforms used by the participant to follow the YouTuber. This variable was not significant. Thus, to answer RQ5, it appears that following YouTubers across different social media platforms does not strengthen tweens’ PSRs.p < 0.05) such that receiving more YouTuber replies to private messages strengthened PSRs. However, receiving a reply from a YouTuber to a comment made was not related to tweens’ PSRs. Thus hypothesis 5 was supported with one measure of communication (receiving private messages) but not the other (receiving comments).Compared to merely seeing a YouTuber across multiple social media platforms, a more powerful predictor of PSRs may be whether a YouTuber directly communicates with a tween through messages or comments. One-third (32.7%) of the participants reported leaving at least one comment for a YouTuber during the “average week.” And although it may seem like a rare occurrence, several participants (11.6%) reported that a YouTuber had responded to their comments. Sending a private message to a YouTuber during an “average week” was rarer, with only 6.8% of the tweens reporting doing so. Only 5.5% of the tweens reported receiving responses to their private messages. Hypothesis 6 predicted that receiving direct communication from a YouTuber would be positively related to tweens PSRs. A hierarchical linear regression see  tested tThe results from the current study suggest that YouTube is embedded in the lives of tweens. Most of the tweens in this sample reported watching YouTube regularly – between 30 and 60 min on the weekends and slightly less than 30 min on weekdays. The amount of time tweens spend on YouTube is interesting, but it may be equally important to know with whom they are watching. The current findings signal that co-viewing YouTube with a parent is rare, while watching alone or with friends is more prevalent. Tweens reported frequently watching YouTube on a personal device such as a mobile phone or tablet. The size and portability of those devices may decrease opportunities for parental co-viewing. If tweens are watching without adults, they may be exposed to more inappropriate content than parents realize.Not only are tweens enthusiastic about watching YouTube content, they are also enthusiastic about their favorite YouTubers. Nearly all participants identified a favorite YouTuber, but there was very little overlap in the YouTubers who were named as favorites. Almost 100 unique YouTube personalities were listed. Many of the YouTubers, like JoJo Siwa and DanTDM appear to be developmentally appropriate for tweens. Yet, many of the YouTubers produce content for mature audiences, such as Logan Paul, who was recently punished by YouTube for posting a video featuring a dead body . The curDespite not knowing much about the content made by these YouTubers, we do know some things about the YouTubers themselves. The first hypothesis predicted that boys would be more likely to list male YouTubers as their favorites, whereas girls would list female YouTubers. The results supported this hypothesis. Boys’ choice of male YouTubers is consistent with previous work on mass media characters e.g., . SeveralResults from the second research question also signal gender differences. Tweens perceived male and female YouTubers to have different attributes. Female YouTubers were rated as more attractive and popular than male YouTubers, and male YouTubers were rated as more violent than female YouTubers. These results reflect a consistent pattern of gender differences between male and female characters seen across television and film in which male characters are portrayed as violent female characters are often young and attractive . Gender The next set of research questions and hypotheses were about wishful identification – the process of wanting to be like a media personality. In this study, tweens’ WI with their favorite YouTuber was positively related to time spent on YouTube, replicating recent findings that children who spend more time watching their favorite vlogger will feel more bonded to him or her . Tweens’YouTuber characteristics also predicted tweens’ WI. Specifically, tweens’ identified more with YouTubers who were perceived as smart and funny. It is encouraging that tweens want to be like media personalities who showcase these positive characteristics. Outside of these shared effects, there were gender differences for WI patterns. It was anticipated that girls would identify more with physically attractive YouTubers, but this was not found. In other words, the current results do not replicate previous work wherein physical attractiveness was the sole predictor of girls’ WI . This chThere is a long history of theory e.g.,  and reseNot only did tweens want to be like their favorite YouTuber, they also reported experiencing feelings of friendship. Results indicated that tweens are forming fairly strong PSRs with their favorite YouTuber. Much like WI, PSRs were positively related to time spent on YouTube and to perceived similarity between the tween and YouTuber. Again, these findings replicate past research in this arena and extend them into the digital realm of YouTube.Tweens’ PSRs were predicted by YouTubers who were humorous. This finding makes sense, as research shows that people who are funny are more socially attractive and likeable . Beyond When examined through the lens of gender schema theory, the results of this study suggest potential for contrasting gender socialization patterns. Not only were there stereotypical gender differences in the perceived attributes of male and female YouTubers, but tween boys and girls formed attachments based on different criteria. Gender schema theory predicts that boys will be paying close attention to the male YouTubers, learning what it means to think and behave like a male. Once the gendered schema for male is in place, this robust cognitive heuristic will be used to (a) filter future incoming information about masculine identities and (b) inform tween boys how to think, feel, and behave as a male should. Similarly, girls will be looking to female YouTubers to demonstrate important components of the female identity. Research should investigate how YouTubers function as role models and influence tweens’ identity development.post hoc regression analyses were conducted parsing out each social media site as a unique independent variable. None of these analyses were significant, confirming that following a YouTuber on other social media platforms is not related to PSRs.Not only do young people follow their real-life friends on social media, but the results of this study show that many tweens also follow their favorite YouTuber “friends” across social media platforms other than YouTube. We anticipated that keeping up with favorite YouTubers across social media platforms would predict tween’s PSRs, but this was not the case. The social media variable was initially computed as a sum score, giving little insight about each individual platform. Consequently, multiple Although following a YouTuber across platforms is not related to PSRs, it makes sense that receiving personal messages from one’s favorite YouTuber may be. Hypothesis 6 predicted that receiving communication from a YouTuber would increase the strength of tweens’ PSRs. This was partially supported. Although receiving a comment from a YouTuber did not relate to PSRs, receiving a private message from a YouTuber was positively related to tweens’ PSRs. It is noteworthy that only eight tweens reported receiving a private message from their favorite YouTuber, demonstrating how powerful this form of communication can be.Contact between a YouTuber and a viewer pushes the boundaries of PSRs into the interpersonal realm. That is to say, what started as a one-sided relationship becomes two-sided when the YouTuber can communicate with the fan. We asked participants if they felt like their favorite YouTuber has become their friend. Over one-quarter (27.8%) of the sample replied “yes.” Many tweens may be experiencing a hyperpersonal parasocial relationship that is mostly one-sided but occasionally becomes interpersonal. Research should explore these new, hyperpersonal parasocial relationships, as they could mediate or moderate other media effects.Like any study, the current research has limitations. The sample consists of tweens from a large, metropolitan area in the southern United States. It is possible that children from other locations experience attachments to YouTubers in a different way. There may also be systematic differences in which tweens opted to participate. Moreover, causal claims cannot be made from cross-sectional data and, as with all self-report research, there could be instances where mood, social-desirability bias, or other factors influenced participants’ survey responses. Longitudinal and/or experimental methods would improve future research in this area. Additionally, some measures in the study  are not-standardized instruments, and this is may limit the generalizability of the results. Finally, the current study operationalized gender in a binary fashion. Tweens are capable of identifying their gender as non-binary or transgender . Future Regardless of these limitations, this study represents an initial attempt to assess tweens’ emotional connections to YouTube personalities. This gap in the literature is regrettable given that children may experience strong attachments to these Internet celebrities. Not only can tweens watch countless hours of content produced by their favorite YouTuber, but they can also buy merchandise, attend events populated with YouTubers, and tune in to see their favorite YouTubers on awards shows. As scholars learn more about PSR and WI, we are beginning to understand the power of these attachments. Consequently, YouTubers stand to act as potent role models, shaping the development of young people’s attitudes and conceptions about gender identity and what it means to be a male and female in today’s society.The datasets generated for this study are available on request to the corresponding author.The studies involving human participants were reviewed and approved by The University of Texas at Dallas. Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.AT and KD were involved in the conceptualization, planning, data collection and analysis, and writing of the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The Modified Vaccinia virus Ankara (MVA) is a highly attenuated vaccinia virus serving as a promising vector vaccine platform to develop vaccines against infectious diseases. In contrast to the well-established replication deficiency and safety of MVA in mammals, much less is known about MVA infection in avian hosts. Here, we used a recombinant MVA expressing fluorescent reporter proteins under transcriptional control of specific viral early and late promoters to study in vivo tropism, distribution, and pathogenesis of MVA infections in embryonated chicken eggs. The chorioallantoic membrane (CAM) of embryonated chicken eggs was inoculated with recombinant MVA, MVA or phosphate-buffered saline. The infection was analyzed by fluorescence microscopy, histology, immunohistochemistry, and virus titration of embryonic tissues. After infection of the CAM, MVA spread to internal and external embryonic tissues with the liver as a major target organ. Macrophages and hematopoietic cells were identified as primary target cells of MVA infection and may be involved in virus spread. Increasing doses of MVA did not result in increased lesion severity or embryonic death. Despite MVA generalization to embryonic tissues, the CAM seems to be the major site of MVA replication. The absence of considerable organ lesions and MVA-associated mortality highlights an excellent safety profile of MVA in chicken hosts. Modified Vaccinia virus Ankara (MVA) was originally generated by Anton Mayr and Eberhard Munz in the 1960s . The attSince the 1990s, MVA has been investigated as a safe vector for the development of recombinant viral vaccines against infectious diseases and cancer. Moreover, MVA is promoted as modern and safe vaccine against smallpox to replace the earlier and fully replication competent VACV vaccines .In contrast to the well-established replication deficiency and safety of MVA-based vector vaccines in mammals, much less is known about MVA infection in avian hosts. Only few studies have been conducted highlighting the usefulness of recombinant MVA as poultry vaccine against various infectious diseases. A single intramuscular inoculation of a recombinant MVA vaccine delivering the hemagglutinin antigen of highly pathogenic avian influenza virus A/Vietnam/1194/04 can protect chickens from a lethal challenge with a high dose of highly pathogenic A/duck/Vietnam/TG24-01/2005 . FurtherAlthough MVA has been adapted to grow in chicken cells and MVA vaccines have been amplified in embryonated eggs , MVA infHere we studied the in vivo tropism, distribution, and pathogenesis of MVA infections in embryonated chicken eggs. We took advantage of an MVA vector expressing two fluorescent reporter proteins and used whole organ imaging, virus titration, histology and immunohistochemistry to monitor the outcome of infections with various amounts of MVA. We show that MVA infection of chicken embryos leads to a generalized spread of virus and to the infection of several types of cells, including macrophages, hepatocytes and cells of the hematopoietic tissues. Surprisingly, MVA infection seems to be well tolerated because even high dose inoculations did not lead to increased incidence of embryonic death.To follow MVA distribution in the chicken embryo, a previously characterized recombinant MVA-GFP-mCherry was used as a reporter virus . BrieflyFertilized eggs from a specific-pathogen-free (SPF) chicken flock  were stored at 16 °C for two days prior to incubation. Eggs were incubated at 37.9 °C and 45% humidity in an incubator  with automated turning of eggs. Eggs were inoculated at embryonic day 11 (ed11) of incubation. Shells were wiped with ethanol and perforated over the air chamber with a power tool. At the inoculation site, a small triangle of the shell was removed. Using a sterile fine dosage syringe with a 30G needle, the shell membrane was perforated and 100 µL of inoculum deposited between the CAM and the inner shell membrane. The hole in the shell was sealed with a transparent tape  and the eggs further incubated without automated rotation to promote sterility at the inoculation site.Eggs were CAM-inoculated with 10³ infectious units (IU) MVA or MVA-GFP-mCherry per embryo. Control embryos were mock-infected with PBS. On days 2–7 post inoculation (2–7 dpi), embryos were necropsied. The experiments were carried out in accordance with institutional and national guidelines for work with genetically modified organisms. No ethical approval was required for this study.At necropsy, the following organs were imaged: Brain, CAM, gonads, heart, intestines, kidneys, liver, lung, proventriculus, spleen, ventriculus, and yolk sack. Proliferative nodules (pocks) on the CAM were scored according to their size: small: ≤1 mm; moderate: 2–5 mm; large: >6 mm.Organs of MVA-GFP-mCherry infected embryos on petri dishes were examined with a ChemiDoc™ MP Imaging system (Bio-Rad Laboratories) and the MacroIllumination Imaging System .Images of native tissue preparations, histological and immunohistochemical slides were taken with an inverted fluorescence microscope  with GFP filter , TexasRed filter , and DAPI filter .After imaging, CAM and organs were processed for histologic examination and viral titration.Tissues for histology were routinely paraformaldehyde-fixed, paraffin-embedded, cut and sections stained with hemalum-eosin.To keep the tension of the CAM during fixation and embedding process, CAMs were dissected with a modified version of Voss’ technique . The fenEscherichia coli  were used as negative controls. Tissues containing macrophages  or orthopoxviruses (MVA-IHC) served as positive controls.IHC was performed with preceding avidin-biotin-block and without epitope retrieval . For macOrgans of chicken embryos were weighed, freeze-thawed three times and homogenized with PBS in a microtube for 45 s at lowest level . After centrifugation , supernatants were stored at −80 °C.Virus infectivities were determined via routine plaque assays performed in duplicate . In 6-we9 IU MVA or MVA-GFP-mCherry and blood samples were collected by piercing the chorioallantoic veins at 4 dpi with a 30G needle connected to a fine dosage syringe. Serum samples were stored at −80 °C. Sera were diluted with saline to obtain a minimal amount of 100 µL and enzyme activities were calculated for the original concentration. Six of eleven undiluted sera were analyzed in parallel to control dilution. Aspartate transaminase (AST), glutamate dehydrogenase (GLDH), and lactate dehydrogenase (LDH) activities were analyzed with a Cobas Integra 400 plus  at the laboratory of the Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, LMU Munich.For serum analysis, embryonated eggs were CAM inoculated with 10Statistical tests and calculations were performed with Microsoft Excel  and GraphPad Prism version 5.04 for Windows .Following established methodology for CAM infections with poxviruses , we inocAs early as 2 dpi, MVA inoculated CAMs displayed defined areas of multiple white, proliferative nodules with diameters of ~1.0–3.5 mm  and the presence of large numbers of inflammatory cells mainly consisting of macrophage-like cells and granulocytes. The proliferation of resident cells and the massive cellular influx at the site of the pock lesion increased the thickness of the CAM about 40-fold to ~1100 µm, compared to the ~25 µm thickness of normal CAM a,b. MoreUsing immunohistochemistry, MVA antigen was detected at 2 dpi in the cytoplasm of ectodermal and mesodermal cells including many putative macrophages and to a lesser extent fibroblasts c. We als2 to 104 IU/g tissue MVA or MVA-GFP-mCherry in livers and lungs of most infected embryos . The correlation of high MVA titers in the CAM with high MVA titers in the liver suggested a direct connection between the infections of these two embryonic tissues.To assess MVA spread from the CAM as the primary site of infection, we analyzed the embryonic organs and extraembryonic tissues for signs of viral replication using the reporter virus MVA-GFP-mCherry. On day 3 pi, we observed multifocal miliary red-fluorescent spots randomly distributed in ~10% of the livers. These red-fluorescent foci also contained fewer cells displaying green fluorescence as revealed upon microscopic examination a,b. Usin embryos d,e. InteHowever, we failed to detect red fluorescence when imaging other organs of the chicken embryos. To characterize the putative spread of MVA infection in more detail, we assessed a large set of organ samples from infected embryos by histology and immunohistochemistry. Indeed, already at 2 dpi we found cell-associated MVA antigen in the tissues of bursa fabricii, heart, intestines, kidneys, skeletal muscle, skin, and ventriculus in many different cell types including endothelial cells, fibroblasts, myocytes , and glomerular mesangial cells. Moreover, we detected MVA antigen in hematopoietic cells in the yolk sack and the bone marrow. Both extravascular (granulopoiesis) and intravascular (erythropoiesis) hematopoietic cells displayed cytoplasmic MVA antigen f. In theInterestingly, we noticed another macroscopic alteration in the infected livers. Starting at 5 dpi, livers of MVA-infected embryos a, and inp > 0.17–0.91) between PBS inoculated and MVA infected chicken embryos , glutamate dehydrogenase (GLDH), and lactate dehydrogenase (LDH) activities were within normal variation and displayed no major or significant differences . In addition, there were no detectable differences when comparing the lesion sizes induced by MVA or MVA-GFP-mCherry infections.The infections with the three MVA doses induced the formation of pock lesions in the CAM with comparable sizes ranging in diameter between 2–5 mm. A significant increase in lesion size corresponding to escalating inoculation doses was not detected. Pearson’s correlation of log10-transformed viral titer in the CAM with pock lesion size was performed in the three dosing groups. There was no significant correlation . Lower viral titers were found in yolk sack, kidney and brain  and embryonic skin lesions did not form upon MVA inoculation . Also inesponses . Thus, tIndeed, these findings are highly encouraging to further investigate the usefulness of recombinant MVA as vaccine vector system for immunization of birds and poultry including in ovo vaccination. In a first in ovo vaccination study in chicken using recombinant MVA, the authors did not observe any adverse effects, but distribution and pathogenesis of MVA infection were not examined . The tho7 IU do not lead to increased mortality, highlighting an excellent safety profile of this attenuated VACV. The chicken embryo infection may also be useful as a model to study virus–avian host interactions. In particular, it might be promising to reassess the function of poxviral proteins known to modulate innate responses of the mammalian immune system. Finally, first promising results from experimental MVA vaccination in poultry and the replication competence of MVA in the embryonated egg support future studies in vaccine development including in ovo vaccination.In summary, CAM inoculation represents an excellent model to study distribution and pathogenesis of different infectious agents, because the CAM is a highly vascularized organ, which functions as major site of gas exchange for the developing chicken. Main target cells of MVA infection in chicken embryos are Kul01+ macrophages, hematopoietic cells and hepatocytes. MVA doses up to 10


Avicenna  who had a special attention toward diseases treatments, gathered results of ages of herbal medicine experiments on humans and animals in his book “Al-Qānūn fī Ṭibb” or "The Canon of Medicine", which is a reliable book in Iranian traditional medicine. The aim of this research was to build a reliable list of plants effective against liver and spleen diseases, based on Avicenna's book (volume 2).By studying the monographs, introduced agents that have been effective in liver and spleen diseases were identified. Upon their origin and effectiveness in diseases of the liver, spleen or both, treatments were organized. From a huge number of drugs, 163 plants from 73 families were found to be effective in treatment of liver and spleen illnesses. In addition, 30 non-herbal agents effective in treatment of liver diseases were detected. The Lamiaceae family have the most effective herbs for treatment of diseases of the liver, spleen or both. Hemp Agrimony, Irsā, and Fūdhanj achieved the highest scores.The effects of different plants on liver and spleen diseases were indicated in Avicenna's book. Due to the report on the above book, further studies needed specially on the effect of Irsā (Iris ensata) and family Lamiaceae on liver and spleen diseases. The largest organ in the body is the liver, comprising about 2 percent of the total body weight; in an adult with average body mass, the liver is about 1.5 kg. The liver performs many different functions including: 1) filtration and storage of blood; 2) metabolism of carbohydrates, proteins, fats, hormones, and foreign chemicals; 3) formation of bile; 4) storage of vitamins and iron; and 5) formation of coagulant factors  and in the West as Avicenna, 980-1037 AD) was an extremely talented individual. Avicenna practiced philosophy, astronomy, geometry, mathematics, and medicine as well as poetry and music. Although medicine was not his main area of interest, he became famous as a physician due to the desperate need for thoughtful medical personnel in the Persian kingdom. Among Avicenna’s works, his medical book Materia Medica) of Canon, Avicenna alphabetically listed about 806 simple medical agents  that were used at the time. Each agent may have different possible general actions, followed by specific properties listed according to symptoms of liver and spleen diseases. In floral monographs of Canon, we found that Avicenna has found that some herbs cure some symptoms so we considered such symptoms and searched for herbs with such properties.Acute liver disease damages the spleen in long term. In Book 2 . This library was created by Dr. Hossein Hatami and is also accessible through the Bu Ali Sina Scientific and Cultural Foundation website . The following versions of the Canon were used in our study: 1) The corrected version of Canon in Persian . Statistical analysis was performed using the Statistical Package for the Social Science (IBM SPSS statistics version 23) program for Windows. Statistical significance of differences between groups was evaluated using non-parametric statistics, the relationship between the numbers of herbs in each family to score of herbs was shown by the Kruskal–Wallis test p<0.05 was considered statistically significant. Graphs were created with Excel 2013 software (Microsoft office 2013).Avicenna introduced 193 agents as they were effective on the liver and spleen. Their characteristics are presented in four categories according to the origin of agent in Plantsnd volume of Canon and found a total of 163 plants used for liver and spleen illnesses. These plants belong to 73 different families. These herbs included medicinal, poisonous, ornamental and economic plants and weeds that are presented in We reviewed all herbs mentioned in the 2The most common effective plants prescribed for liver or spleen diseases or both, are shown in AnimalsThe majority of the 17 agents of animal’s origin including animal, organs or animal physiological fluids used as medication. In certain cases, especially for insects, the whole body was used, and in other cases, the animal’s urine or even the milk was used. The animals and their applications are presented in The used animals can be divided into groups according to their availability, such as domesticated animals, such as jennet, goat, camel, cow, and others such as locust and worms. Wild animals, for example, wolf, sand grouse, red-headed partridge, hedgehog, porcupine, antelope, and stag. Various organs, and products of exotic animals, species such as Spanish fly, coral, oyster have been used in order to cure liver and spleen diseasesMineralsWe were able to identify 8 materials of mineral origin . The useAgents of other originsFive medicinal agents that were processed from animal or plant materials or agents of mixed or unknown origin are presented in The overwhelming majority (84.45%) of agents that served as simple drugs were derived only from plants see . The proBased on our survey of Canon, 163 herbal parts which exert therapeutic effects on the liver and spleen, were found. In this book, some items refer to one herb Ṭarfūlis and Ṭūqriūs both refer to Teukrion or some items are parts of one herb and have different names e.g. Ḥiltit is gum and Maḥrūth is the root of Anjudhān so the last two have same scientific name of Asafoetida in the Tables. In old manuscripts, there are different descriptions for identical herb so different scientific names have been proposed for the same herb. Prof. Ghahraman and Prof. Okhovvat have introduced appropriate scientific names for old names; in the present study, we used scientific names according to their suggestions  was named "The eupatorion of Avicenna"  which has the highest score (Mentha piperita) which also gained a high score was used successfully by Avicenna as a drug, for treatment of liver and spleen diseases. It was shown that M. piperita causes lipid peroxidation and hepatic damage in a dose-dependent manner  is another high-score herb which exhibits hepatoprotective action partly through microsomal drug metabolizing enzymes (MDME) inhibitory action (Gilani and Janbaz, 1995According to the number of effects that every herb has, as prescribed by Avicenna as effective on liver or spleen diseases or both, the herbs were scored . Ghāfithst score , on the These results show a need for a close scrutiny in methods of planting, harvesting, processing, extraction and preparing a single or combination formula that affects remedies and practice of ancient medicine. In order to prepare a suitable herbal drug for the treatment of complicated diseases such as liver cirrhosis and hepatocellular carcinoma, according to Avicenna book, further studies are needed to make an effective drug for liver or spleen diseases is promising.nd volume of Canon, we prepared a list of agents that are effective in three main areas namely, liver, spleen, and liver & spleen diseases. The current study indicates the necessity of deep analysis, study and further assessment of listed items.Through analysis of 806 therapeutic items of Avicenna 2


The World Health Organization’s (WHO’s) response to population ageing is to promote healthy ageing across the life-course. Healthy ageing is the process of developing and maintaining the functional ability that enables well-being in older age.Endorsed in 2016, WHO’s Global Strategy and Action Plan on Ageing and HealthA second action plan on ageing and health, a Decade of Healthy Ageing (2020–2030), is under preparation. In 2020, WHO will also issue a global baseline report. The report will quantify the baseline indicators of healthy ageing; provide projections of Member State-endorsed outcome and impact indicators through 2030; and suggest ways to increase impact between 2020 and 2030 through illustrative, evidence-informed interventions that would enable countries to improve older adults’ intrinsic capacities and functional ability.In 2017, WHO launched the International Consortium on Metrics and Evidence for Healthy Ageing consisting of policy-makers, members of civil society and researchers from all WHO regions. This consortium conducts research and evidence synthesis on healthy ageing, with work progressing to inform the baseline report. Here, we argue that this work and other efforts should promote inclusive dialogue between policy and scientific evidence for several reasons. First, the perspective and priorities of policy-makers in ministries and national institutes can guide the provision of evidence. Eight case studies from Chile, China, Finland, Ghana, India, Qatar, Singapore and Thailand, representing all WHO regions, are currently examining how evidence is being used by stakeholders to inform policy, make programmatic decisions and identify interventions that can improve the lives of older persons. These national case studies will identify common and distinct challenges, highlighting the importance of context-specific variation that can influence how policies are developed and what contributes to impact. For example, community-based organizations and social innovations can bridge health and social services at home and in communities,International classification of functioning, disability and health,–Second, tracking progress on healthy ageing over the coming decade should reflect collective benchmarking.Finally, evidence-informed decisions are required to increase impact. Evidence syntheses can be contributions to policy, guidance and research priorities. Ways to scale up promising pilot projects, ensure cost–effectiveness in diverse settings and reduce research waste, are further areas for improvement. Clinical trial evidence for chronic disease management is important; however, research on person-centred outcomes should be prioritized, using outcomes that older persons find meaningful, such as meeting basic needs, learning and making decisions, mobility, building and maintaining relationships, and contributing to families, communities or society – all of which are components of functional ability.


Ejecta with a size much larger than the mean particle size of feedstock powder have been observed in powder bed fusion additive manufacturing, both during post-process sieving and embedded within built components. However, their origin has not been adequately explained. Here, we test a hypothesis on the origin of large (much larger than the mass-median-diameter of feedstock powder) ejecta—that, in part, they result from stochastic, inelastic collisions of ejecta and coalescence of partially-sintered agglomerates. The hypothesis is tested using direct observation of ejecta behavior, via high-speed imaging, to identify interactions between ejecta and consequences on melt pool formation. We show that stochastic collisions occur both between particles which are nearly-simultaneously expelled from the laser interaction zone and between particles ejected from distant locations. Ejecta are also shown to perturb melt pool geometry, which is argued to be a potential cause of lack-of-fusion flaws. The process, which relies on sequential melting of powder layers on the order of tens of microns in thickness, is useful for the production of complex, previously un-manufacturable, geometries. However, significant challenges remain in understanding the complex material transfer and heat transfer mechanisms which take pace during the many melting and re-melting cycles during processing. In particular, the mechanism leading to the formation of ejecta (e.g. spatter), commonly observed during processing, and their influence on build quality remains in dispute.Laser powder bed fusion additive manufacturing (PBFAM), a subcategory of metal 3D printing technology, is rapidly emerging as an important industrial manufacturing technology for aerospace, medical, and defense applications4. More recently, high-speed imaging has been used to argue that ejecta primarily forms, not as a result of melt ejection, but due to evaporation-driven entrainment of powder5. Though, according to Ly et al.5, when melt ejection does occur in PBFAM, it tends to produce ejecta on the order of 25–100 μm in size. This is because the kinetic energy of ejected melt must exceed the capillary pressure of the melt (surface tension divided by the melt’s radius of curvature). Hence, larger melt droplets are more likely to be ejected; powder enhances this effect by hindering forward motion of the melt. Nevertheless, entrained particles—of a similar size distribution as the feedstock powder particles—are argued to form approximately 85% of spatter. Of this portion, about 60% are described as “hot”5.To date, little is known regarding the mechanisms by which spattered particles form or how they influence flaw formation processes in powder bed fusion additive manufacturing. Models of the PBFAM process have proven useful in better understanding melt pool dynamics and in showing that melt ejection and powder denudation play important roles in the process6 reinforces, and adds to, the findings of Ly et al.5. Again, evaporation-driven entrainment of particles, due to flows of metal vapor and ambient gas, is identified as the primary mechanism for spatter formation. The proportion of hot particles also appears to depend on environmental pressure6. Interestingly, both works6 maintain that larger spatter particles are likely due to melt ejection, while entrained particles have similar size distributions to the feedstock powder. Though it should be noted that Ly et al.5 do show the formation of large particles through the collision and merging of neighboring, hot droplets expelled from the melt pool. More recently, Bidare, Bitharas, et al.8 used high-speed imaging and modeling to demonstrate the complex nature of plume-powder-melt interactions and argue that sintering and melting of denuded particles contributes to the formation of large ejecta. Additionally, their work7 shows that coalescence of partially-sintered agglomerates can occur due to entrainment of agglomerates into the vapor plume and subsequent melting. Another mechanism, suggested by Körner, Bauereiss et al.10 based on simulations of electron-beam PBF, involves melting and coalesce of powder, at the edge of electron-beam-melted tracks, by interaction with superheated melt droplets.High-speed X-ray imaging of the PBFAM process11; (2) large spatter particles may remain un-melted and become incorporated into the component13; or, (3) large ejecta may shadow the beam and thus contribute to lack-of-fusion defects10. Among these potential mechanisms, (2), and (3) are more likely since perturbations in powder height are not an uncommon occurrence in PBFAM, typically resulting from interactions of the recoater with elevated or thermally-deformed parts on the build plate15. It is also not generally accepted that such powder perturbations lead to defects. In contrast, it has been shown12 that flaws containing unmelted powder, and an associated reduction in tensile strength, result from processing with powder contaminated with a large number of spattered particulates that are roughly three times the diameter of virgin powder. It is therefore critical for the formation of defect-free PBFAM components that the mechanism for the formation of large ejecta be understood and, if possible, mitigated.It has been speculated that ejecta atop the powder bed may contribute to flaws in one of three ways: (1) spatter particles dragged during powder recoating may perturb the powder bed causing height variationset al.5, who reported collision and merging of nearly-simultaneously expelled particles, and the findings of Bidare et al.7, who reported coalescence of partially-sintered agglomerates via entrainment into the vapor plume. Also, for the first time, large ejecta are also shown to interfere with the intended melt geometry, which is argued to be a potential cause of lack-of-fusion flaws.Our results indicate that melt ejection is not the sole mechanism for the formation of large ejecta particles. Rather, we show that large ejecta (much larger than the mass-median-diameter of feedstock powder) form as a result of stochastic, inelastic collisions of ejecta and coalescence of partially-sintered agglomerates. We present evidence that stochastic collisions occur both between neighboring particles, defined as those which are nearly-simultaneously expelled from the laser interaction zone, and between distant particles, defined as those ejected from distant locations. These results reinforce some of the findings of Ly The primary results of this work are elucidations of mechanisms for the formation of large ejecta and evidence that such ejecta affect melt pool geometry. Here, two mechanisms for the formation of large, spheroidal ejecta are investigated: stochastic, inelastic collision of ejecta and coalescence of partially-sintered agglomerates. Evidence of interference of large ejecta with melt pool formation is also reported and argued to contribute to the formation of lack-of-fusion flaws.The formation of large, spheroidal ejecta was observed to occur via multi-body collisions. Collisions were observed to occur between particles ejected from distant locations as well as between neighboring, near-simultaneously-expelled ejecta.A collision between particles ejected from distant locations is shown in Fig. 18 and agglomerate, though any effects appear to be minor in this case.Immediately after collision, the spheroidal agglomerate moves at a speed of approximately 0.2 m/s. Given the comparable sizes of the particles and the speed of the expelled particle, this is a significantly slower speed than can be expected for a completely inelastic collision of two solid particles. Additionally, the trajectory of the agglomerate is slightly altered after collision. Both observations perhaps indicate that the previously-expelled ejectum may have been partially-sintered to the underlying substrate. Argon shielding gas, directed from the bottom to the top of each image frame at an approximate speed of 1.5 m/s, may also have an influence on the trajectory and speed of the particleCollision between neighboring, near-simultaneously-expelled ejecta is a second mechanisms identified for the formation of large, spheroidal agglomerates. An example of this phenomena is provided in Fig. 18. It is noteworthy that in this case, the velocity of the spheroidal agglomerate is perpendicular to the shielding gas, and appears to be only slightly affected by the shielding gas within the observable field of view. Given the upward trajectory of the agglomerate, the shielding gas may affect the ultimate landing location of the agglomerate17.Careful analysis of the high speed video data appears to show that ejecta emerge from along the sides of the laser-interaction zone and are accelerated backwards, relative to the direction of laser scanning. Based on their smoothness and dark appearance, which indicate significant reflection of the illumination laser, the ejecta are at least partially molten when they emerge from the laser-interaction zone and after collision. It is unclear if the ejecta are a product of powder entrainment into the vapor or melt ejection. In either case, the backwards acceleration and seemingly curved path of the particles appears to be at least partially due to the influence of the vapor plume, as illustrated in Fig. et al.8 Though, this was not explicitly called out by the authors. Ly et al.5 have also documented the formation of large particles through the collision and merging of neighboring, hot droplets expelled from the melt pool, though over a much shorter distance than presented here.It ought to be noted that the formation of a large agglomerate through the collision of neighboring, near-simultaneously-expelled ejecta has previously been shown in supplementary high-speed images accompanying the works of Bidare, Bitharas, The plume also appears to contribute to heating, motion, and coalescence of partially-sintered agglomerates. This is most readily observed during laser glazing, where there is significantly less obstruction of the process by entrained powder. A laser glazing case is shown in Fig. et al.7 This mechanism is illustrated in Fig. It is proposed that the rapid melting and coalescence of the cluster observed in Fig. It is also noteworthy that just before the apparent interaction of the cluster with the vapor plume  ejecta:Evidence of interference of large ejecta with melt pool formation are also reported. Such interactions between large ejecta and the melt pool are shown to significantly perturb the intended track geometry in one of two ways. Ejecta can shadow or block the laser beam then be expelled from the laser-interaction zone, or can be incorporated into the melt pool and, under some circumstances, perturb the intended track geometry. It is argued that either mechanism may lead to lack of fusion and may explain the observation of stochastic (i.e. random or rogue) defects in PBFAM.Additional work is required to further understand and model the mechanism which lead to the formation of large ejecta and the contribution of the identified mechanisms, together with melt ejection. The interaction of ejecta and the melt during scanning of hatches and contours also poses a critical and underexplored topic in powder bed fusion additive manufacturing. The physics underlying these interactions are not trivial and require significant additional development of current, multi-physics numerical models if the problem is to be addressed in practice. As such, no attempt has been made here to model these phenomena. Nevertheless, this wok provides insight into little-explored interaction mechanisms that should inform the development of physics-based simulations and the optimization of the PBFAM process.Ongoing work seeks to quantify the likelihood of the detailed interactions and establish a causal link between interactions and flaw formation. While the captured and analyzed data includes over 70 gigabytes of video, this only represents 30 layers of buildup of a very small component (or roughly 6 meters of laser travel). Most PBFAM components are composed of many thousands of layers, each with a cross-section many times that of our test specimen, representing kilometers of laser travel. The captured subset is thus too small to extrapolate the likelihood of the identified mechanisms in commercial PBFAM processes. Nevertheless, each mechanism was identified at least once in a well-controlled environment during the course of our very small sampling period. So, while it appears that the identified mechanisms may be quite significant for commercial PBFAM processes, we are wary to extrapolate the likelihood of occurrence of the identified mechanisms for the formation of large ejecta or for the interference of large ejecta with melt pool formation.Experiments were carried on a 3D Systems ProX-320 PBFAM machine. The system utilized a 500 W (max power) fiber laser with an output wavelength of 1070 ± 10 nm. The feedstock material was nickel alloy 625 (Inconel® 625) powder with a particle size distribution of 11–53 µm. Powder was spread using a 3D Systems flexible, polymer recoater. A flow of argon gas traveled above and across the build plate, perpendicular to the recoating direction, at a speed of approximately 1.5 m/s, measured by a mini-vane anemometer. The build geometry consisted of a 5 mm diameter cylinder built using default processing parameters  were captured at 37,500 frames per second (27 µs per frame-spacing) with a frame exposure time of 25 µs. Within the high-speed video and images reported here, the argon gas across the build plate was oriented such that it traveled from the bottom to the top of each frame. The bottom of each frame represented the axis parallel to and closest to the front of the ProX-320 machine. Each video was manually post-triggered by observing the deposition process. For video captures of sequential layers, the build process was paused between layers to allow transmission of data from camera to external storage. Approximately 10 minutes were required to transmit 10,000 frames, with each layer requiring a minimum of ~11,000 frames. Over 70 gigabytes of video data were collected and manually analyzed—this represents buildup of approximately 30 layers.Supplementary Video S1Supplementary Video S2Supplementary Video S3Supplementary Video S4Supplementary Video S5


Clinical practice guidelines contain recommendations for physicians to determine the most appropriate care for patients. These guidelines systematically combine scientific evidence and clinical judgment, culminating in recommendations intended to optimize patient care. The recommendations in CPGs are supported by evidence which varies in quality. We aim to survey the clinical practice guidelines created by the American College of Gastroenterology, report the level of evidence supporting their recommendations, and identify areas where evidence can be improved with additional research.We extracted 1328 recommendations from 39 clinical practice guidelines published by the American College of Gastroenterology. Several of the clinical practice guidelines used the differing classifications of evidence for their recommendations. To standardize our results, we devised a uniform system for evidence.A total of 39 clinical practice guidelines were surveyed in our study. Together they account for 1328 recommendations. 693 (52.2%) of the recommendations were based on low evidence, indicating poor evidence or expert opinion. Among individual guidelines, 13/39 (33.3%) had no recommendations based on high evidence.Very few recommendations made by the American College of Gastroenterology are supported by high levels of evidence. More than half of all recommendations made by the American College of Gastroenterology are based on low-quality evidence or expert opinion. It is estimated that 60 to 70 million Americans are affected by gastrointestinal (GI) diseases which may manifest as diarrhea, gas, bloating or abdominal pain. These syNot all CPG recommendations should be given equal weight. The recommendations in CPGs contain supporting evidence which ranges from high quality  to low quality (expert opinion). To grade the strength of recommendations and the quality of evidence underlying recommendations in guidelines, the ACG utilizes the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. By takinWith the increasing amount of CPGs, systematic reviews, and randomized controlled trials (RCTs), it is reasonable to assume that CPG recommendations would be based on a greater degree of high-quality evidence. UnfortunThe ACG has published 43 CPGs as of June 2017. We obtaiThese CPGs provided a list of references and an assessment of individual study quality. Based on the results of these assessments, guideline authors assign a strength of evidence grade to each recommendation published in the summary of recommendations section in the CPG. The ACG uses the GRADE approach to assess strength of recommendations and the quality of evidence. While many of the classifications of evidence are uniform, there were several CPGs that used differing definitions . To standardize our results, we devised a uniform evidence taxonomy based on the varying definitions provided by authors of individual CPGs . BrieflyWe conducted a content analysis based on the methodology of Wright et al.(8) SM obtained CPG’s produced by the ACG from their website. SM then extracted each recommendation into an Excel spreadsheet with its associated level of evidence. We also stratified the list by the guideline in which they were published along with the year of publication. Following extraction, we used the evidence taxonomy  to assigUlcerative Colitis in Adults - had over 50% of recommendations supported by high evidence.A total of 39 clinical practice guidelines were surveyed in our study. Together they account for 1328 recommendations. 693 (52.2%) of the recommendations were based on low evidence, indicating poor evidence or expert opinion. 436 recommendations (32.8%) were based on moderate evidence. 199 (15%) of recommendations were based on high evidence, such as those found in multiple randomized controlled trials or systematic reviews. Only one guideline—The year 2010 had the highest percentage of recommendations supported by high evidence , whereas 2016 had the lowest rate of high evidence . The year 2016 had the highest rate of low evidence , and 2011 had the fewest recommendations supported by low evidence . Between 2010 and 2016, the percentage of recommendations supported by high evidence decreased every year (45.8% to 4.2%). From 2011 to 2016, the rate of low evidence supporting published recommendations increased every year (16.7% to 85.6%). Among individual guidelines, 13 of 39 (33.3%) had no recommendations based on high evidence. These guidelines address the prevention, treatment, or management of colorectal cancer, GI bleeding, achalasia, liver disease, IBD, Lynch Syndrome, or others. Of these 13, four were based solely on low evidence.The ACG has current guidelines for clinical practice dating back to 2007. The 39 guidelines we surveyed contained 1328 recommendations. Over half (52.2%) were based on low evidence, and only 15% were based on high evidence. A similar study conducted on the American College of Emergency Physicians (ACEP) CPGs found that less than 10% of their recommendations were based on high-quality evidence, and the majority of recommendations were based on expert opinion. The AmerRCTs are the cornerstone of clinical decision making, and the field of gastroenterology has a poor history of producing influential RCTs. Nearly 2For example, Koh et al. reported a 36% increase in recommendation number for the American Association for the Study of Liver Diseases (AASLD) since their development in 1998. But despite this substantial increase, less than 15% were based on high-grade evidence.Since 2003, the National Institutes of Health (NIH) budget for digestive disease research has plateaued, while corporate funding for gastroenterology research has dropped by more than 60% since 2008.,20 This The goal of the ACG research program is to strengthen the capabilities of GI specialists, advance patient care, and create high-quality guidelines. Some stuLow-level evidence recommendations are often based on expert opinion. When creating guidelines from expert consensus they are subject to bias. Conflicts of interest (COI) are potential sources of bias in the development of CPGs. A 2017 sAnother major problem in basing recommendations on expert consensus is the fact that opinions vary between experts. This is illustrated in a study where Marras et al. found the highest percent of expert agreement on any recommendation was 81%. Without Our study only evaluated CPGs published by the ACG and therefore is not generalizable outside of gastroenterology. Additionally, our study is not generalizable towards other ACG quality measures such as Appropriate Use Criteria, or other published literature. Because some of the guidelines were published before the current year, they may not be an accurate reflection of the current levels of evidence in gastroenterology literature, and therefore our study may underestimate the current research quality in the field. For some recommendations, establishing a randomized controlled trial may not be possible, and thus achieving a high level of evidence is unlikely.More than half of all recommendations made by the ACG are based on low-quality evidence or expert opinion. Thirteen of the 39 CPGs implemented by the ACG contain no recommendations supported by high-level evidence. Research should be focused on developing randomized control trials and systematic reviews to improve the evidence supporting CPGs.S1 Table(DOCX)Click here for additional data file.S2 Table(DOCX)Click here for additional data file.