the study population was composed of youth at the time of entry into a weight management program who enrolled in the determinants of change in childhood obesity ( decco ) study , a prospective , observational study examining determinants of health indicators at baseline and during weight management in an established weight management program .
all subjects aged 517 , with no untreated endocrine disorder , were eligible for study participation .
participants in the decco study had four study visits  baseline ( enrollment in weight management program ) , 6 months , 1 year , and 2 years ( 1 year after completion of monthly program)whereas this analysis considers only the baseline data in a cross - sectional manner .
written informed consent was provided by the legal guardian and the child provided signed assent .
the study was approved by the institutional review board at the hamilton health sciences corporation ( hamilton , on , canada ) .
the baseline study visit occurred in the morning , after an 8- to 12-h fast ( allowing water ) , and comprised an evaluation of cardiometabolic risk factors ( including an ogtt ) , anthropometric evaluation , and completion of questionnaires as described below .
bmi ( kg / m ) and bmi z score were calculated based on centers for disease control and prevention normative data , using nutstat , a component of the epi info program ( 15 ) .
waist circumference ( wc ) was measured half - way between the iliac crest and lower rib ( 16 ) using a nonstretching tape with attached spring balance pulled to a tension of 250 g. wc z scores were calculated based on age- and sex - specific canadian normative data ( 17,18 ) . blood pressure ( bp )
was measured three times on the right arm , using an oscillometric method ( omron healthcare , inc . ,
lake forest , il ) with appropriate - sized cuff after the children had been sitting at rest for 10 min ( 19 ) .
age , sex , and height cutoffs for defining hypertension were based on the 95th centile using u.s .
normative data as recommended ( 19 ) . parents reported the family history of premature coronary heart disease ( defined as events in first- or second - degree male relatives < 55 years old and/or female relatives < 65 years old ) , t2 dm , and obesity .
children aged 8 years completed a confidential questionnaire identifying their cigarette smoking history and self - assessed pubertal stage ( 20,21 ) .
boys and girls aged < 8 years were assumed to be prepubertal , based on normative data for pubertal onset .
an ogtt was conducted as follows : a baseline venous blood sample was taken and the patient consumed 1.75 g / kg glucose solution up to a maximum of 75 g orally .
prediabetes was defined as ifg , igt , or ifg + igt using ada criteria ( ifg : fasting glucose level 5.6
baseline laboratory analyses were conducted in the laboratory of hamilton health sciences and included plasma glucose , total cholesterol ( tc ) , hdl cholesterol ( hdl - c ) , and triglyceride ( tg ) ; ldl cholesterol ( ldl - c ) was calculated using the equation of friedewald ( 22 ) .
glucose was measured using an enzymatic reference method with hexokinase , and cholesterol levels were measured with an enzymatic colorimetric method on a roche integra analyzer .
mmol / l and/or hdl - c < 1.03 mmol / l and/or ldl - c > 3.3 mmol / l , according to current recommendations ( 23 ) .
study participants with dysglycemia were compared with those without dysglycemia using an unpaired t test for continuous variables and  test for discrete variables .
laboratory variables ( tc , hdl - c , ldl - c , tg , glucose , hemoglobin a1c ( hba1c ) alanine aminotransferase [ alt ] , and aspartate aminotransferase [ ast ] ) were log transformed to improve normality and are presented in table 1 as geometric means and 95% cis .
all other continuous variables are presented as mean  sd and discrete variables as n ( % ) .
the ada currently recommends criteria for screening for t2 dm in children ( table 2 ) .
the sensitivity and specificity of these criteria for identifying dysglycemia ( t2 dm , ifg , and igt ) and isolated igt in our population were calculated . to examine the association of risk variables with dysglycemia ,
logistic regression analysis was used and odds ratios ( ors ) were calculated . the sensitivity and specificity of other risk strategies
were also evaluated including 1 ) current canadian diabetes association ( cda ) guidelines ( 24 ) , 2 ) a risk score developed by reinehr et al .
the cda recommends screening all subjects in puberty or aged 10 years who have two of the following : bmi > 95th centile , high - risk ethnic group or family history of t2 dm , signs or symptoms of insulin resistance , and/or use of antipsychotic medications .
( 4 ) developed a simple risk score that includes parental history of t2 dm ( 2 points ) , pubertal onset ( 1 point ) , and extreme obesity defined as bmi z score > 2.58 ( 1 point ) and recommended screening children or youth with 2 points .
( 3 ) recommended doing an ogtt to identify igt in children or youth if the fpg exceeded 4.8 mmol / l . as we were primarily interested in reducing the number of ogtts
performed , while detecting patients with isolated igt , several models for the prediction of isolated igt were developed from least invasive to most complex .
variables that were significant in univariate analysis were included ( age , sex , family history of t2 dm , systolic bp [ sbp ] , bmi z score , wc , hba1c , fpg , elevated alt , tc - to - hdl ratio , and tg ) .
model 1 included data available with history and clinical exam only ; model 2 included data from history , clinical exam , and nonfasting blood work ( hba1c ) ; model 3 included data from history , clinical exam , hba1c and fasting glucose ; and model 4 added in the influence of fasting tg . to evaluate the predictive properties of current ada and cda screening criteria and each model to identify igt , we performed receiver operating characteristic ( roc ) analysis on the entire population with complete data . to estimate the discriminative value of the predictive models
, we calculated the roc area under the curve ( auc ) for the outcome igt .
the auc for the ada and cda screening criteria and each of the models was compared using a  test .
although the models were developed using continuous variables , we sought to establish a user - friendly screening test using thresholds for each variable and to examine these in a logistic model .
the applied thresholds considered were previously recommended , including bmi z score 2.58 ( 4 ) and hba1c 5.7% , or were obtained using optimal discrimination on the roc curve ( tg > 1.17 mmol / l ) .
the baseline study visit occurred in the morning , after an 8- to 12-h fast ( allowing water ) , and comprised an evaluation of cardiometabolic risk factors ( including an ogtt ) , anthropometric evaluation , and completion of questionnaires as described below .
bmi ( kg / m ) and bmi z score were calculated based on centers for disease control and prevention normative data , using nutstat , a component of the epi info program ( 15 ) .
waist circumference ( wc ) was measured half - way between the iliac crest and lower rib ( 16 ) using a nonstretching tape with attached spring balance pulled to a tension of 250 g. wc z scores were calculated based on age- and sex - specific canadian normative data ( 17,18 ) .
blood pressure ( bp ) was measured three times on the right arm , using an oscillometric method ( omron healthcare , inc . ,
lake forest , il ) with appropriate - sized cuff after the children had been sitting at rest for 10 min ( 19 ) .
age , sex , and height cutoffs for defining hypertension were based on the 95th centile using u.s .
parents reported the family history of premature coronary heart disease ( defined as events in first- or second - degree male relatives < 55 years old and/or female relatives < 65 years old ) , t2 dm , and obesity .
children aged 8 years completed a confidential questionnaire identifying their cigarette smoking history and self - assessed pubertal stage ( 20,21 ) .
boys and girls aged < 8 years were assumed to be prepubertal , based on normative data for pubertal onset .
an ogtt was conducted as follows : a baseline venous blood sample was taken and the patient consumed 1.75 g / kg glucose solution up to a maximum of 75 g orally .
prediabetes was defined as ifg , igt , or ifg + igt using ada criteria ( ifg : fasting glucose level 5.6 mmol / l ; igt : 2-h glucose level 7.8
baseline laboratory analyses were conducted in the laboratory of hamilton health sciences and included plasma glucose , total cholesterol ( tc ) , hdl cholesterol ( hdl - c ) , and triglyceride ( tg ) ; ldl cholesterol ( ldl - c ) was calculated using the equation of friedewald ( 22 ) .
glucose was measured using an enzymatic reference method with hexokinase , and cholesterol levels were measured with an enzymatic colorimetric method on a roche integra analyzer .
dyslipidemia was defined as fasting tg > 1.7 mmol / l and/or hdl - c < 1.03 mmol / l and/or ldl - c > 3.3 mmol / l , according to current recommendations ( 23 ) .
study participants with dysglycemia were compared with those without dysglycemia using an unpaired t test for continuous variables and  test for discrete variables .
laboratory variables ( tc , hdl - c , ldl - c , tg , glucose , hemoglobin a1c ( hba1c ) alanine aminotransferase [ alt ] , and aspartate aminotransferase [ ast ] ) were log transformed to improve normality and are presented in table 1 as geometric means and 95% cis .
all other continuous variables are presented as mean  sd and discrete variables as n ( % ) .
the ada currently recommends criteria for screening for t2 dm in children ( table 2 ) .
the sensitivity and specificity of these criteria for identifying dysglycemia ( t2 dm , ifg , and igt ) and isolated igt in our population were calculated . to examine the association of risk variables with dysglycemia ,
the sensitivity and specificity of other risk strategies were also evaluated including 1 ) current canadian diabetes association ( cda ) guidelines ( 24 ) , 2 ) a risk score developed by reinehr et al .
( 4 ) , and 3 ) fasting glucose > 4.8 mmol / l ( 3 ) . the cda screening criteria are similar to the ada criteria but somewhat less stringent .
the cda recommends screening all subjects in puberty or aged 10 years who have two of the following : bmi > 95th centile , high - risk ethnic group or family history of t2 dm , signs or symptoms of insulin resistance , and/or use of antipsychotic medications .
( 4 ) developed a simple risk score that includes parental history of t2 dm ( 2 points ) , pubertal onset ( 1 point ) , and extreme obesity defined as bmi z score > 2.58 ( 1 point ) and recommended screening children or youth with 2 points .
( 3 ) recommended doing an ogtt to identify igt in children or youth if the fpg exceeded 4.8 mmol / l . as we were primarily interested in reducing the number of ogtts
performed , while detecting patients with isolated igt , several models for the prediction of isolated igt were developed from least invasive to most complex .
variables that were significant in univariate analysis were included ( age , sex , family history of t2 dm , systolic bp [ sbp ] , bmi z score , wc , hba1c , fpg , elevated alt , tc - to - hdl ratio , and tg ) .
model 1 included data available with history and clinical exam only ; model 2 included data from history , clinical exam , and nonfasting blood work ( hba1c ) ; model 3 included data from history , clinical exam , hba1c and fasting glucose ; and model 4 added in the influence of fasting tg . to evaluate the predictive properties of current ada and cda screening criteria and each model to identify igt , we performed receiver operating characteristic ( roc ) analysis on the entire population with complete data . to estimate the discriminative value of the predictive models
, we calculated the roc area under the curve ( auc ) for the outcome igt .
the auc for the ada and cda screening criteria and each of the models was compared using a  test .
although the models were developed using continuous variables , we sought to establish a user - friendly screening test using thresholds for each variable and to examine these in a logistic model .
the applied thresholds considered were previously recommended , including bmi z score 2.58 ( 4 ) and hba1c 5.7% , or were obtained using optimal discrimination on the roc curve ( tg > 1.17 mmol / l ) .
the descriptive characteristics and risk variables of the cohort ( n = 259 ) and of those with and without dysglycemia ( prediabetes or t2 dm ) are presented in table 1 . although the mean age was 11.8 years , participants ranged in age from 5 to 17 years . of the participants , 1 ( 0.39% ) had undiagnosed t2 dm based on a 2-h glucose > 11.1 mmol / l .
prediabetes was present in 20.5% of the cohort , and 4.2% had ifg , 13.9% isolated igt , and 2.3% ifg + igt .
thus , of the 53 participants with prediabetes identified using an ogtt , 36 ( 68.0% ) had isolated igt and would not have been identified if only fasting glucose had been measured .
we identified no difference in the prevalence of prediabetes in those < 10 vs. 10 years ( 17.8 vs. 22.0% ; p = 0.45 ) .
baseline characteristics of the study cohort the participants with dysglycemia ( prediabetes or t2 dm ) did not differ in age , self - reported pubertal stage , ethnicity , bmi z score , wc z score , or percent body fat from those without dysglycemia ( table 1 ) .
a family history of t2 dm was relatively common in the children in this cohort ( 50.2% ) , and the prevalence was not different in those with and without dysglycemia . diagnosed t2 dm in at least one parent was less common ( 16.2% ) but also did not differ between groups .
children with dysglycemia had higher sbp and diastolic bp ( dbp ) , fasting tg , hba1c , and alt .
the prevalence of elevated alt was also higher in the dysglycemia group ( 13.0 vs. 4.9% ; p = 0.03 ) , but no differences in the prevalence of dyslipidemia ( p = 0.07 ) or hypertension ( p = 0.14 ) were noted .
the prevalence of hba1c above the recommended threshold of 5.7% was not different in those with dysglycemia ( p = 0.10 ) .
the strongest predictor of dysglycemia in univariate analysis was hba1c ( or per 1-sd increment 3.4 [ 95% ci 1.249.35 ] ; p = 0.02 ) .
other cardiovascular risk factors that predicted dysglycemia included serum tg ( 1.87 [ 1.332.63 ] ; p = 0.0003 ) and sbp ( 1.04 [ 1.011.07 ] ; p = 0.01 ) .
the ada recommends screening children aged 10 years ( or pubertal children ) who are overweight or obese and have two associated risk factors as described in table 2 .
current screening criteria had a sensitivity of 38.9% ( 95% ci 25.951.9 ) and a specificity of 69.8% ( 63.576.0 ) to detect dysglycemia . in a similar manner ,
the sensitivity to detect isolated igt was 41.7% ( 25.657.8 ) with specificity of 69.5% ( 63.575.6 ) .
thus , in applying the current ada screening criteria , less than half of those children with isolated igt were identified .
as noted in table 3 , reinehr score and fpg > 4.8 mol / l also had low sensitivity and comparable specificity to the ada criteria .
the cda criteria had higher sensitivity to identify a child with igt ( 81.8 vs. 43.2% using ada ) but lower specificity ( 37.7 vs. 70.2% ) .
ada - recommended criteria for screening children and youth for t2 dm sensitivity and specificity of current screening guidelines , published scores , and simple tg model for detecting isolated igt as described in research design and methods , we proceeded to develop the models based on increasing complexity .
we compared the models using the auc of the roc curves ( table 4 ) . adding hba1c or elevated alt values to data obtained from the clinical history and physical exam
did not improve the prediction of igt , but adding fasting blood work was beneficial . adding fasting glucose alone demonstrated no increased predictive power , but adding fasting tgs did .
similar conclusions were reached if the anthropometric variable included was bmi z score or wc z score .
roc analysis of models for prediction of isolated igt using ada criteria using thresholds for each variable in model 4 , the potential predictors age > 10 ( p = 0.49 ) , pubertal ( p = 0.52 ) , parental t2 dm ( p = 0.15 ) , hba1c > 5.7% ( p = 0.43 ) , fasting blood glucose ( p = 0.85 ) , sbp > 95th centile ( p = 0.82 ) , and bmi z score > 2.58 were not significant and were not included in the final logistical model .
remaining in the model was tg > 1.17 mmol / l ( or 4.3 ; p < 0.0001 ) .
this variable alone had clinical usefulness ( table 3 ) , and auc that exceeded the ada and cda screening criteria was somewhat lower than continuous models 4a and 4b ( table 4 ) .
current ada screening criteria had low discriminatory capacity for identifying dysglycemia in our cohort of overweight children presenting to a weight management program . using a specific multilevel approach to applying screening criteria ,
we have identified a screening algorithm requiring history and physical examination only , with comparable discriminatory capacity ( auc in roc analysis ) to ada recommendations but requiring less information ( age , sex , parent history of t2 dm , sbp , and bmi z score ) .
the addition of a nonfasting blood test to measure hba1c did not improve the predictive properties , but adding a fasting tg improved the discriminatory capacity .
in fact , a fasting tg > 1.17 mmol / l had better discriminatory capacity and clinical usefulness than current ada criteria in identifying isolated igt .
dysglycemia was common ( 20.8% ) and igt was identified in 16.2% of the participants , comparable to the findings of several american studies ( 2,25 ) .
silent t2 dm was relatively rare in this population ( 1 of 259 ) but was identified on a 2-h blood glucose alone . as with previous studies ,
the prevalence of ifg was low , and 68% of children with elevated 2-h glucose levels
had fasting glucose < 5.6 mmol / l ( ada cutpoint for ifg ) . among our population of obese children and adolescents , important risk predictors for
sbp , parental t2 dm , and higher tc - to - hdl ratio were also predictive variables .
important variables without evident influence include age , pubertal stage , sex , body size ( bmi ) , and wc , suggesting that among obese youth , these variables have little predictive potential for dysglycemia .
current ada screening criteria had low sensitivity and only moderate specificity to identify isolated igt .
using roc analysis , we identified a model using history , physical examination , and fasting laboratory data ( glucose and tg ) with better discrimination of igt than current ada and cda screening criteria .
this may enable reasonable identification of children with prediabetes while avoiding excessive use of ogtts .
hba1c thresholds recently have been recommended for identifying adults at high risk for t2 dm and for diagnosis of t2 dm in adults ( 26 ) .
this approach also has been recommended recently for adolescents , although the clinical usefulness in this age - group has since been challenged ( 27,28 ) . using national health and nutrition examination survey data , hba1c thresholds of 5.7 and 6.0% had poorer performance in identifying prediabetes in adolescents compared with adults .
we found no added predictive benefit of including hba1c with data from history and physical examination in identifying igt .
however , adding the fasting tg level improved the auc . when applying thresholds to develop a simple clinically applicable version of model 4 , only fasting tg > 1.17 mmol / l remained in the model , and this alone had sensitivity of 70% and specificity of 64% to identify igt .
furthermore , the auc exceeded that of current ada and cda screening methods . despite being one of very few studies to critically examine the usefulness of current screening recommendations to identify prediabetes in obese youth , our study does have some limitations . even though no influence of pubertal stage was identified on prevalence of prediabetes
, it is noteworthy that puberty was not assessed by a physician but was self - reported by the study participants using a validated methodology .
although we identified no difference in prevalence of prediabetes in those aged < 10 compared with those 10 years , only 73 participants aged < 10 were included .
thus , further observation of the prevalence of prediabetes and evaluation of appropriate screening criteria in this age group should occur .
our classification of the glycemic status of the study participants was based on a single ogtt , and given published concerns on the reliability of this measure , we may have misclassified some of the participants .
however , our methodology is consistent with that used in most studies examining the risk of progression to t2 dm and comparable studies identifying the prevalence of prediabetes in youth .
finally , our evaluation was within a select population : all children and youth were overweight , 93% were obese , and all were referred for weight management .
balancing the costs and the consequences of more invasive testing with the potential health advantages of screening depends on how important one considers the identification of a disorder .
although in adults we have interventions that prevent the progression of prediabetes to t2 dm , thus arguing for high importance of identification of prediabetes , questions remain on the natural history of prediabetes in youth .
8 of 33 ( 24% ) youth with igt at baseline progressed to t2 dm during a 2-year period ( 1 ) , comparable to annual progression rates of 510% reported in adults ( 6 ) .
should future research support the importance of intervening in children and youth with igt , screening criteria with high sensitivity would be required .
although screening obese children and youth with a fasting tg provides moderate sensitivity and specificity and is better than currently recommended approaches , 30% of obese children with igt will not be identified using this screening criteria , suggesting that an ogtt be done in all obese children and youth .
 objectiveto examine the performance of current screening recommendations for detecting dysglycemia in children and adolescents with obesity.research design and methodsin a cross - sectional study , an oral glucose tolerance test and demographic ( age , sex , family history of diabetes , and ethnicity ) , clinical ( bmi z score , waist circumference , and pubertal stage ) , and laboratory variables used in current pediatric screening criteria for type 2 diabetes mellitus were measured in 259 overweight or obese youth aged 517 years . 
 glycemic status was based on american diabetes association ( ada ) thresholds . the performance ( sensitivity and specificity ) of current screening criteria and newly developed models to identify isolated igt 
 were compared.resultsdysglycemia was present in 20.8% of the cohort . 
 of the 54 participants with dysglycemia , 68% had a normal fasting glucose and were identified with the 2-h glucose test . 
 current ada criteria had low sensitivity ( 41.7% [ 95% ci 25.657.8 ] ) and moderate specificity ( 69.5% [ 63.575.6 ] ) to identify igt . in receiver operating characteristic ( roc ) analysis 
 , the addition of hemoglobin a1c ( hba1c ) or fpg did not improve the roc area under the curve ( auc ) ( hba1c : 0.64 vs. 0.63 ; p = 0.54 ; hba1c + fpg : 0.66 ; p = 0.42 ) , but adding triglyceride level did ( auc 0.72 vs. 0.63 ; p = 0.03 ) . a simple model with fasting triglyceride level > 1.17 mmol / l improved auc compared with ada screening criteria ( 0.68 vs. 0.57 ; p = 0.04).conclusionsthe prevalence of igt is high among obese children and youth . 
 current screening criteria have low sensitivity to detect isolated igt . 
 although adding nonfasting laboratory values to history and physical measures does not improve diagnostic accuracy , adding fasting lipid profile improves predictive value . 