whole blood viscosity ( wbv ) is one of virchow 's triad , which is an established concept of three phenomena including stasis , endothelial dysfunction and atherothrombosis that ultimately lead to , and/or result from cardiovascular complications[14 ] . each phenomenon represents a subclinical vascular process , which in turn is indicated by a clinical pathology index . specifically , wbv is an intrinsic resistance of blood flow in the vascular system , and index for stasis . increase in wbv is a potential risk factor for future cardiovascular disease . in current clinical practice considering the implication of stasis in metabolic diseases , its clinical management with antiplatelet and the controversies regarding antiplatelet and its bleeding complications[79 ] , such usage is under - utility . international normalized ratio ( inr ) is used to determine the clotting tendency of blood and the need for anticoagulant ( especially warfarin ) therapy . normal range is about 1.0 for a healthy person , and 2.0 - 3.5 for people who are on anticoagulant therapy . a higher inr level indicates a high tendency of bleeding complications , whereas lower inr level is indication of high risk of having a thrombotic event in patients who are on anticoagulant therapy . thus , while anticoagulant and antiplatelet are used interchangeably , there is an established laboratory index ( inr ) being employed for routine monitoring to assess contraindication to and/or need for anticoagulant ; but none for antiplatelet . the objective of this work is to establish whether difference in wbv level is associated with different levels of inr and platelet count . it would be expected , and thus hypothesized that a patient with low inr requiring anticoagulant therapy should present with higher wbv . the findings from this study would provide evidence to suggest wbv as a potential laboratory index to assess for contraindication to antiplatelet therapy synonymous to how inr is being used for anticoagulants . it is supported materially by the albury south west pathology  a unit of western pathology cluster of nsw health australia . one year of de - identified archived clinical pathology data for the period of january to december 2008 was audited . 7387 cases ( female - male ratio = 3528 - 3859 ) for international normalizing ratio , which were concomitantly tested from one phlebotomy collection point for full blood count ( fbc ) haematocrit and total proteins , were extracted . haematocrit results from the fbc were used in conjunction with total protein to extrapolate wbv values based on previously published algorithm . whether whole blood viscosity differs between normal vs. high international normalizing ratio and thrombocytopenia vs. thrombocytosis were evaluated . inr level was commonly determined arithmetically from the result of prothrombin time using the formula inr = ptpatient / ptnormal inr data for this study were determined with this formula included in a standard operational procedure ( sop ) . the sop included measurement of prothrombin time ( pt ) by quantitative analysis using the sysmex ca540 method and inr calibration curve , which is plotted for every new lot of pt reagent . results of inr were reported with the following interpretative consideration to risk of bleeding 
 normal patients  no therapy = 1.0anitcoagulated patient = 2.0  3.5 including 
 prophylaxis for prosthetic heart valves = 2.5  3.5all other indications = 2.0  3.0 
 critical results for anticoagulated patients = < 1.5 or > 4.5 
  normal patients  no therapy = 1.0 anitcoagulated patient = 2.0  3.5 including 
 prophylaxis for prosthetic heart valves = 2.5  3.5all other indications = 2.0  3.0 
  prophylaxis for prosthetic heart valves = 2.5  3.5 all other indications = 2.0  3.0 critical results for anticoagulated patients = < 1.5 or > 4.5 in this study , numerical levels of inr results have been used as reported . it was assumed on the premise of the hypothesis that a pathology that impacts on inr should also impact on platelet count and wbv . the data were sorted by wbv results and categorized into three groups of low , normal or high wbv levels based on the continuum of 15.00 , 15.01 - 19.01 and 19.02 respectively . high , normal and low wbv were named groups i , 2 and 3 respectively . in the statistical analysis , it was considered to avoid errors due to unequal sample size such as exaggerating the effects of inequality of variance . the high wbv ( group 1 ) had the least number ( n = 173 ) and was used as the base sample size for the sub - groups . the discretional criterion for selection of [ n = 173 ] from the other two groups was to make the comparison be between the lowest - median - highest intervals in ranking ( fig . 1 ) . therefore , the lowest [ n = 173 ] in the low wbv rank and the median [ n = 173 ] in the wbv groups were selected . to determine association of high , normal or low wbv with inr and platelet count , multivariable analysis of variance ( manova ) indication of selections from the ranks of wbv - groups . 1 - 173 , 2102 - 2274 , 7215 - 7387 , 173 , g1 , g2 & g3 : hyperviscosity , normoviscosity and hypoviscosity groups respectively , r : ranking , s : selection for statistical analysis . the complete data set were further re - analyzed thrice to observe for consistency in result . first , data were sorted by , and selection of ( n = 173 ) from groups 2 and 3 were repeated to match for age and gender . second , data were sorted by inr . the top ( n = 120 ) vs. the bottom ( n = 120 ) were selected to represent high vs. low inr sub - groups respectively and wbv level was compared between the sub - groups . the top ( n = 120 ) vs. the bottom ( n = 120 ) were selected to represent thrombocytosis vs. thrombocytopenia sub - groups respectively and wbv level was compared between the sub - groups . the statistics of the groups for the complete data set are presented in table 1 . the result shows that platelet count increases with whole blood viscosity or vise versa , whereas low viscosity is associated with high inr ( table 1).manova show that levels of international normalizing ratio and platelet counts statistically significantly differs between different ranges of whole blood viscosity levels ( p<0.001 ) . platelet count is statistically significantly lower in low whole blood viscosity compared to hyperviscosity and normoviscosity ( p<0.001 ) . conversely , international normalized ratio is statistically significantly higher in low whole blood viscosity compared to hyperviscosity ( p<0.001 ) and normoviscosity ( p<0.002 ) . no difference was observed between hyperviscosity and normoviscosity in platelet count or international normalized ratio ( fig . 2 ) . comparison of inr & plt between wbv - groups . 1 - 3 : hyperviscosity , normoviscosity and hypoviscosity groups respectively , inr : international normalized ratio , plt : platelet count x10/l , wbv : whole blood viscosity . in the repeat analyses for observation of consistency , manova on the age and gender matched data set also showed statistical significance ( p<0.005 ) . wbv was observed to statistically significantly differ between high vs. low inr ( p<0.001 ) , as well as between thrombocytopenia vs. thrombocytosis ( p<0.005 ) ( fig . inr : international normalized ratio , plt : platelet count x10/l , wbv : whole blood viscosity . this study reports observation of significantly higher level of inr associated with lower level of wbv . this observation is in consonance with the study 's hypothesis and has relevant applicability in clinical practice . on one hand , it affirms that the use of anticoagulant therapy is in tandem with relative high wbv level . more importantly on the other hand , low wbv being associated with relative high inr , whereby the latter indicates risk of bleeding , suggests that blood viscosity can be utilized as a laboratory index of contraindication / indication to anticoagulant and/or antiplatelet therapies . the issue is that inr is mainly used to assess the status of extrinsic ( clotting ) pathway in order to determine indication / contraindication for anticoagulant therapy . neither is wbv assessed on the chronic patients , nor is the risk of bleeding complication of less concern . therefore , if the latter is assessed to determine possible risk of bleeding complication anticoagulant , chronic disease patients who are not qualified for inr assessment , but who are to be treated with antiplatelet would benefit from assessment of wbv . a recommended guideline is not to prescribe antiplatelet if contraindicated[1720 ] . yet , lack of laboratory assessment of compliance is an acknowledged major issue . the report provides insight to assessment of hypoviscosity as part of antiplatelet drug monitoring and in compliance to guidelines and good evidence - based clinical practice . further , this study reports observation of significantly higher and lower level of platelet count associated with high and low wbv respectively . it is known that antiplatelet therapy is employed in the management of hyperviscosity / stasis through modulation of platelet hyperreactivity . therefore , it is not out of place that relative high platelet count is associated with high blood viscosity . this logic is not in line with the fact that several studies have reported an association between platelet hyperreactivity after antiplatelet therapy . nevertheless , platelet function can be measured by different methods and platelet counting has been in use , except that the usage to monitor antiplatelet drugs is not common . factors that increase wbv include haematocrit , total plasma protein , erythrocyte aggregation , erythrocyte deformability and oxidative stress . in current clinical practice , a low platelet count is a factor that determines temporary stopping chemotherapy , but not antiplatelet therapy . this observation of thrombocytopenia associated with low blood viscosity provides evidence to suggest that low platelet count is also occasion to consider stopping any antiplatelet therapy . a review has reported gender - specific differences in platelet function and response to antiplatelet therapy . the report further acknowledged role for laboratory monitoring of antiplatelet medications in predicting individual responsiveness . the results from this study show that age and gender differences may not impact on the association between wbv and inr or platelet count . in corroboration with previous observation of infrequent prevalence of hyperviscosity in thromboembolic state (  whole blood viscosity issues ii on this series ) , it surmises that platelet count should necessarily be used as adjunct laboratory index to determine indication or contraindication for antiplatelet therapy . it is known that thrombocytopenia is associated with bleeding complications[2628 ] . what this article contributes is that inr , platelet count and wbv are laboratory indices to consider in constituting antiplatelet monitoring panel . the observations also corroborate with previous report to suggest putting into perspective the specificity of wbv relative to stasis . in addition , the result indicates that wbv identify individuals in whom anticoagulant and antiplatelet therapies may be contraindicated  that is , from the association and clinical utility of inr . perhaps , one question is : will hypoviscosity be associated with gastrointestinal bleeding to prove evidence of being a possible contraindication index ? this report presents that higher level of inr is associated with lower level of wbv and vise versa , whereas thrombocytopenia is associated with hypoviscosity . the results indicate that wbv identifies individuals in whom anticoagulant and antiplatelet therapies are indicated or contraindicated . the findings suggest that inr , platelet count and wbv are laboratory indices to consider in constituting antiplatelet monitoring panel .