Hemoglobin A1c assay variations and implications for diabetes screening in obese youth

11-Oxyandrogens in Adolescents With Polycystic Ovary Syndrome

Context

Polycystic ovary syndrome (PCOS) is common and diagnosis requires an elevated testosterone. The clinical importance of adrenal 11-oxyandrogens in PCOS is unclear.

Objective

We sought to determine if 11-oxyandrogens 1) better identify PCOS diagnosis compared to testosterone, 2) predict clinical comorbidities of PCOS, and 3) are altered with an combined oral contraceptive pill (COCP) or metformin therapy.

Methods

Data from 200 adolescent female participants aged 12 to 21 years, most with obesity, enrolled across 6 studies in pediatric endocrinology were included: 70 non-PCOS controls, 115 untreated PCOS, 9 PCOS + obesity treated with COCP, and 6 PCOS + obesity treated with metformin. 11-Hydroxyandrostenedione (11-OHA4), 11-hydroxytestosterone (1-OHT), 11-ketotestosterone (11-KT), and testosterone were measured with liquid chromatography-tandem mass spectrometry. Data between 1) untreated PCOS and controls and 2) untreated PCOS and the 2 treatment groups were compared.

Results

Untreated girls with PCOS had higher 11-OHA4 (P = .003) and 11-OHT (P = .005) compared to controls, but not 11-KT (P = .745). Elevated 11-OHA4 remained statistically significant after controlling for obesity. Testosterone better predicted PCOS status compared to 11-oxyandrogens (receiver operating characteristic curve analysis: 11-OHA4 area under the curve [AUC] = 0.620, 11-OHT AUC = 0.638; testosterone AUC = 0.840). Among untreated PCOS patients, all 3 11-oxyandrogens correlated with hirsutism severity. 11-KT (P = .039) and testosterone (P < .006) were lower in those on COCP treatment compared to untreated PCOS. Metformin treatment had no effect on 11-oxyandrogens, although testosterone was lower (P = .01).

Conclusion

Although 11-oxyandrogens do not aid in the diagnosis of PCOS, they relate to excess hair growth. COCP treatment may related to 11-KT; however, further work is needed to determine causality, relationship with metabolic outcomes, and the clinical utility of measuring these androgens in PCOS.

Short-Term Change in Measures of Glycemia in Obese Youth Meeting Criteria for Prediabetes: A Retrospective Chart Review

BACKGROUND

The prevalence of youth diagnosed with prediabetes is increasing, yet there is a lack of guidelines on how to manage this condition clinically.

OBJECTIVES

The aim was to determine the short-term outcomes of patients referred with prediabetes and to determine predictors of worsening dysglycemia in youth.

STUDY DESIGN

This is a retrospective chart review of patients referred to our Youth Diabetes Prevention Clinic (YDPC) with laboratory tests indicating an increased risk for type 2 diabetes (T2D). We defined glycemic categories by HbA1c with normoglycemia as HbA1c <5.7%, prediabetes I (P1) as HbA1c 5.7 to <6.0%, and prediabetes II (P2) as HbA1c 6.0 to <6.5%. We compared HbA1c at the time of referral (screening HbA1c) and at the YDPC visit (YDPC HbA1c) to assess for improvement or worsening. Multinomial logistic regression was used to assess predictors of prediabetes.

RESULTS

Among 562 patients seen, 336 had both screening and YDPC HbA1c values. Race (p < 0.001) and screening glycemic category (p < 0.001) were significantly associated with dysglycemia at the YDPC visit, while sex (p = 0.50), BMI z-score change (p = 0.27), and days from referral (p = 0.83) were not. As compared to those who reverted to normoglycemia, patients with prediabetes at YDPC were 7 times more likely to have a higher screening HbA1c (both P1 and P2). The majority of patients referred with prediabetes had lower HbA1c at the YDPC (75.4-82.6%).

CONCLUSION

Patients with screening HbA1c <6% might benefit from a 4-month follow-up at primary care while recommending lifestyle changes. Patients of minority race and screening HbA1c ≥6% are more likely to have a persistent elevation of HbA1c.

Clinical profile at diagnosis with youth-onset type 1 and type 2 diabetes in two pediatric diabetes registries: SEARCH (United States) and YDR (India)

BACKGROUND

Over the last decades, diabetes in youth has increased in both India and the United States, along with the burden of long-term complications and healthcare costs. However, there are limited standardized population-based data in contemporary youth cohorts for comparison of clinical and demographic characteristics of diabetes for both type 1 (T1D) and type 2 (T2D).

METHODS

In partnership, we harmonized demographic and clinical data from the SEARCH for Diabetes in Youth (SEARCH) registry in the United States and the Registry of People with Diabetes with Youth Age at Onset (YDR) in India to the structure and terminology of the Observational Medical Outcomes Partnership Common Data Model. Data were from youth with T1D and T2D, aged <20 years and newly diagnosed between 2006 and 2010. We compared key characteristics across registries using χ2 tests and t-tests.

RESULTS

In total, there were 9650 youth with T1D and 2406 youth with T2D from 2006 to 2012. SEARCH youth were diagnosed at younger ages than YDR youth for T1D and T2D (10.0 vs 10.5 years, P < .001 and 14.7 vs 16.1 years, P < .001, respectively). For T2D, SEARCH had a higher proportion of females and significantly lower proportion of youth of high socioeconomic status compared to YDR. For T1D and T2D, SEARCH youth had higher BMI, lower blood pressure, and lower A1c compared to YDR youth.

CONCLUSIONS

These data offer insights into the demographic and clinical characteristics of diabetes in youth across the two countries. Further research is needed to better understand why these differences exist.

Oral glucose tolerance test does not affect degree of hemoglobin glycation as measured by routine assay

BACKGROUND

Hemoglobin A1c (HbA1c) is an accurate index of fluctuation in glycemia over the 2-3 months prior to quantitative assessment. During this time, hemoglobin (Hb) slowly glycates until it shows the properties of advanced glycation end-products. Glycation kinetics is intensified by prolonged glucose exposure. In subjects undergoing oral glucose tolerance testing (OGTT), immediately after ingestion, glucose is ostensibly transported by the glucose transporter 1 (GLUT1) to erythrocyte corpuscular hemoglobin. The earliest significant measurable level of hemoglobin glycation associated with this transportation is still not clear.

SUBJECTS AND METHODS

We attempted to explore the early impact of short-term glucose load on HbA1c levels, because it is now known that transmembrane GLUT1-mediated glucose transport occurs immediately. A total of 88 participants (46 patients and 42 clinically healthy controls) underwent fasting plasma glucose quantitation during an OGTT. HbA1c, revealed by a monoclonal anti-glycation epitope antibody and adiponectin, was quantitated before (T0) and 2 hours (T120) after 80 g glucose ingestion.

RESULTS

Wilcoxon test revealed that the HbA1c values did not significantly vary (P=0.15) during the OGTT, whereas glucose concentration varied strongly between T0 and T120.

DISCUSSION

It is well known that quantitative estimation of HbA1c is informative for clinical care, independently of glucose level. The molecular mechanisms and dynamics by which glucose enters/exits red blood cells are incompletely known and may differ between individuals. We here show, for the first time, that HbA1c levels do not significantly increase during OGTT, supporting the view that non-enzymatic glycation of hemoglobin occurs slowly and that glycation during the 2 hours of an OGTT is insignificant.

Pediatric Clinical Endpoint and Pharmacodynamic Biomarkers: Limitations and Opportunities

Medical research in children typically lags behind that of adult research in both quantity and quality. The conduct of rigorous clinical trials in children can raise ethical concerns because of children's status as a 'vulnerable' population. Moreover, carrying out studies in pediatrics also requires logistical considerations that rarely occur with adult clinical trials. Due to the relatively smaller number of pediatric studies to support evidence-based medicine, the practice of medicine in children is far more reliant upon expert opinion than in adult medicine. Children are at risk of not receiving the same level of benefits from precision medicine research, which has flourished with new technologies capable of generating large amounts of data quickly at an individual level. Although progress has been made in pediatric pharmacokinetics, which has led to safer and more effective dosing, gaps in knowledge still exists when it comes to characterization of pediatric disease and differences in pharmacodynamic response between children and adults. This review highlights three specific therapeutic areas where biomarker development can enhance precision medicine in children: asthma, type 2 diabetes mellitus, and pain. These 'case studies' are meant to update the reader on biomarkers used currently in the diagnosis and treatment of these conditions, and their shortcomings within a pediatric context. Current research on surrogate endpoints and pharmacodynamic biomarkers in the above therapeutic areas will also be described. These cases highlight the current lack in pediatric specific surrogate endpoints and pharmacodynamic biomarkers, as well as the research presently being conducted to address these deficiencies. We finally briefly highlight other therapeutic areas where further research in pediatric surrogate endpoints and pharmacodynamic biomarkers can be impactful to the care of children.

Screening for cystic fibrosis-related diabetes and prediabetes: Evaluating 1,5-anhydroglucitol, fructosamine, glycated albumin, and hemoglobin A1c

OBJECTIVE

Dysglycemia is prevalent in cystic fibrosis (CF) but screening with annual oral glucose tolerance tests (OGTT) can be burdensome. We investigated alternate glycemic markers-hemoglobin A1c (HbA1c), 1,5-anhydroglucitol (1,5AG), fructosamine (FA), and glycated albumin (GA)-as screening tests for CF-related diabetes (CFRD) and pre-diabetes (CFPD) in youth with CF as defined by the gold-standard OGTT 2-hour glucose (2hG).

METHODS

Youth 10 to 18 years with CF had a 1,5AG, FA, GA, HbA1c, and 2-hour OGTT collected. Correlations between all glycemic markers and 2hG were evaluated. Area under the receiver operative characteristic (ROC-AUC) curves were generated. Optimal cut points for predicting CFPD (2hG ≥ 140 mg/dL) and CFRD (2hG ≥ 200 mg/dL) were determined.

RESULTS

Fifty-eight youth with CF were included (2hG < 140, n = 16; CFPD, n = 33; CFRD, n = 9; 41% male, mean ± SD age 14.2 ± 3.6 years, BMI z-score 0.0 ± 0.8, % predicted forced expiratory volume in 1 second [FEV1] 89.9 ± 15.1, % predicted forced vital capacity [FVC] 103.2 ± 14.6). ROC-AUC's for all alternate markers were low for CFPD (0.52-0.67) and CFRD (0.56-0.61). At a cut point of 5.5%, HbA1c had 78% sensitivity (95% CI: 0.45-0.94) and 41% specificity (95% CI: 0.28-0.55) for identifying CFRD, correlating to a ROC-AUC of 0.61 (95% CI: 0.42-0.8).

CONCLUSIONS

All alternate markers tested demonstrate poor diagnostic accuracy for identifying CFRD by 2hG.

Health Outcomes of Youth in Clinical Pediatric Weight Management Programs in POWER

OBJECTIVE

To describe treatment outcomes of children and adolescents enrolled in the Pediatric Obesity Weight Evaluation Registry, a consortium of multicomponent pediatric weight management programs in the US.

STUDY DESIGN

This multicenter prospective observational cohort study, established in 2013, includes youth (2-18 years of age) with obesity enrolled from 31 Pediatric Obesity Weight Evaluation Registry (POWER) sites over a 2-year period and followed up to 12 months. Weight status was evaluated by the percentage of the 95th percentile for body mass index (%BMIp95). Associations of weight status outcomes with patient characteristics and program exposure were analyzed with multivariable mixed effects modeling.

RESULTS

We included 6454 children and adolescents (median age, 11 years; IQR, 9-14 years; 53% white, 32% Hispanic; 73% with severe obesity) who were enrolled in POWER. Median changes in %BMIp95 for this cohort were -1.88 (IQR, -5.8 to 1.4), -2.50 (IQR, -7.4 to 1.8), -2.86 (IQR, -8.7 to 1.9), at 4-6, 7-9, and 10-12 of months follow-up, respectively (all P < .05). Older age (≥12 years), greater severity of obesity, and Hispanic race/ethnicity were associated with better improvement in %BMIp95. A 5-percentage point decrease in %BMIp95 was associated with improvement in cardiometabolic risk factors.

CONCLUSIONS

Overall, treatment in pediatric weight management programs is associated with a modest median decrease in BMI as measured by change in %BMIp95. Further studies are needed to confirm these findings, as well as to identify additional strategies to enhance the effectiveness of these multicomponent interventions for youth with severe obesity.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02121132.

Assessment of disturbed glucose metabolism and surrogate measures of insulin sensitivity in obese children and adolescents

BACKGROUND

With the rising prevalence of obesity and type 2 diabetes (T2D) in obese children, it is becoming imperative to detect disturbed glucose metabolism as early as possible in order to prevent T2D development.

SUBJECTS/METHODS

Cross-sectional study of 92 obese children (median age 11.7 years, 51% female) and 7 lean children (median age 11.4 years, 57% female) who underwent an oral glucose tolerance test (OGTT) in a tertiary pediatric care center. Glucose tolerance was assessed and different indices for β-cell function, insulin sensitivity and insulin secretion were calculated.

RESULTS

Nineteen obese children were identified with prediabetes (PD, 12 impaired glucose tolerance, 4 increased fasting glucose and 3 combined). Compared with the 73 obese children with normal glucose tolerance (nGT), subjects with PD had higher insulin resistance, but lower insulin sensitivity and β-cell function, although their glycated hemoglobin (HbA1c) levels were comparable. The Whole Body Insulin Sensitivity Index (WBISI) and β-cell function by Insulin Secretion-Sensitivity Index-2 (ISSI-2) strongly correlated with the OGTT glucose area under the curve 0-120 min (r = 0.392, p < 0.0002; r = 0.547, p < 0.0001, respectively). When testing the relation between early insulin response during OGTT by insulinogenic index and insulin sensitivity assessed by WBISI, a hyperbolic relationship between insulin secretion and insulin sensitivity was found. The calculated disposition index was lower in subjects with PD vs. nGT (median 459 vs. 792, p = 0.004). We identified the OGTT 30-min/120-min insulin ratio as a simple marker, which is significantly lower in obese children with vs. without PD (median 0.87 vs. 1.29, p = 0.021) and which has a better sensitivity and specificity for detecting PD than HbA1c among obese children.

CONCLUSIONS

Children with identified PD had changes of several markers for β-cell function, insulin sensitivity and resistance before changes in HbA1c occurred. The lower disposition index indicates that these children have already inadequate β-cell compensation for the degree of insulin resistance.

Alternate glycemic markers reflect glycemic variability in continuous glucose monitoring in youth with prediabetes and type 2 diabetes

OBJECTIVE

To determine whether the alternate glycemic markers, fructosamine (FA), glycated albumin (GA), and 1,5-anhydroglucitol (1,5AG), predict glycemic variability captured by continuous glucose monitoring (CGM) in obese youth with prediabetes and type 2 diabetes (T2D).

STUDY DESIGN

Youth with BMI ≥85th%ile, 10-18 years, had collection of fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), FA, GA, and 1,5AG and 72 hours of CGM. Participants with HbA1c ≥5.7% were included. Relationships between glycemic markers and CGM variables were determined with Spearman correlation coefficients. Linear models were used to examine the association between alternate markers and CGM measures of glycemic variability-standard deviation (SD) and mean amplitude of glycemic excursions (MAGE)-after controlling for HbA1c.

RESULTS

Total n = 56; Median (25th%ile, 75th%ile) age = 14.3 years (12.5, 15.9), 32% male, 64% Hispanic, 20% black, 13% white, HbA1c = 5.9% (5.8, 6.3), FA=211 mmol/L (200, 226), GA= 12% (11%, 12%), and 1,5AG = 22mcg/mL (19, 26). HbA1c correlated with average sensor glucose, AUC, SD, MAGE, and %time > 140 mg/dL. FA and GA correlated with average and peak sensor glucose, %time >140 and >200 mg/dL, and MAGE. GA also correlated with SD and AUC180. 1,5AG correlated with peak glucose, AUC180, SD, and MAGE. After adjusting for HbA1c, all 3 markers independently predicted MAGE; FA and GA independently predicted SD.

CONCLUSIONS

Alternate glycemic markers predict glycemic variability as measured by CGM in youth with prediabetes and T2D. After adjusting for HbA1c, these alternate markers continued to predict components of glycemic variability detected by CGM.

Comparison of A1C to Oral Glucose Tolerance Test for the Diagnosis of Prediabetes in Overweight and Obese Youth

IN BRIEF This study reports performance of A1C against the oral glucose tolerance test (OGTT) in predicting prediabetes among overweight and obese African-American and Caribbean children. A retrospective chart review was completed for 230 children. Receiver operating characteristic curves were generated to find the predictive performances of different tests against the OGTT. A1C alone is a poor discriminator of prediabetes in our study population, with low sensitivity (70%) and specificity (48.8%). BMI z score, A1C, and homeostatic model assessment of insulin resistance are significant predictors of prediabetes and, when taken together, provide better discrimination for prediabetes.

Examining trends in prediabetes and its relationship with the metabolic syndrome in US adolescents, 1999-2014

AIMS

We sought to investigate temporal trends in prediabetes prevalence among US adolescents using two definitions and evaluate relationships with obesity and a MetS-severity score.

METHODS

We evaluated data from 5418 non-Hispanic white, non-Hispanic black, and Hispanic adolescents aged 12-19 participating in the National Health and Nutrition Examination Survey 1999-2014 with complete data regarding MetS and hemoglobin A1c (HbA1c). Prediabetes status was defined by American Diabetes Association (ADA) criteria: fasting glucose 100-125 mg/dL or HbA1c 5.7%-6.4%. MetS severity was assessed with a MetS-severity Z-score.

RESULTS

Prevalence of prediabetes as defined by HbA1c abnormalities significantly increased from 1999-2014, while prevalence of prediabetes as defined by fasting glucose abnormalities showed no significant temporal trend. There were variations in these trends across different racial/ethnic groups. MetS Z-score was overall more strongly correlated with HbA1c, fasting insulin, and the homeostasis model of insulin resistance than was BMI Z-score. These correlations were true in each racial/ethnic group with the exception that in non-Hispanic white adolescents, in whom the MetS Z-score was not significantly correlated with HbA1c measurements.

CONCLUSION

We found conflicting findings of temporal trends of US adolescent prediabetes prevalence based on the ADA's prediabetes criteria. The increasing prevalence of prediabetes by HbA1c assessment is concerning and raises the urgency for increased awareness and appropriate measures of prediabetes status among physicians and patients.

Performance of point-of-care HbA1c test devices: implications for use in clinical practice - a systematic review and meta-analysis

BACKGROUND

Point-of-care (POC) devices could be used to measure hemoglobin A1c (HbA1c) in the doctors' office, allowing immediate feedback of results to patients. Reports have raised concerns about the analytical performance of some of these devices. We carried out a systematic review and meta-analysis using a novel approach to compare the accuracy and precision of POC HbA1c devices.

METHODS

Medline, Embase and Web of Science databases were searched in June 2015 for published reports comparing POC HbA1c devices with laboratory methods. Two reviewers screened articles and extracted data on bias, precision and diagnostic accuracy. Mean bias and variability between the POC and laboratory test were combined in a meta-analysis. Study quality was assessed using the QUADAS2 tool.

RESULTS

Two researchers independently reviewed 1739 records for eligibility. Sixty-one studies were included in the meta-analysis of mean bias. Devices evaluated were A1cgear, A1cNow, Afinion, B-analyst, Clover, Cobas b101, DCA 2000/Vantage, HemoCue, Innovastar, Nycocard, Quo-Lab, Quo-Test and SDA1cCare. Nine devices had a negative mean bias which was significant for three devices. There was substantial variability in bias within devices. There was no difference in bias between clinical or laboratory operators in two devices.

CONCLUSIONS

This is the first meta-analysis to directly compare performance of POC HbA1c devices. Use of a device with a mean negative bias compared to a laboratory method may lead to higher levels of glycemia and a lower risk of hypoglycaemia. The implications of this on clinical decision-making and patient outcomes now need to be tested in a randomized trial.

Prediabetes in Pediatric Recipients of Liver Transplant: Mechanism and Risk Factors

OBJECTIVE

To investigate the role of calcineurin inhibitor exposure and states of insulin resistance-obesity and adolescence-in prediabetes after pediatric liver transplant via oral glucose tolerance testing, which previously has not been done systematically in these at-risk youths.

STUDY DESIGN

This was a cross-sectional study of 81 pediatric recipients of liver transplant. Prediabetes was defined as impaired glucose tolerance (IGT; glucose ≥140 mg/dL at 2 hours) or impaired fasting glucose (IFG, ≥100 mg/dL). Corrected insulin response (CIR) was calculated as measure of insulin secretion, corrected for glucose (CIR₃₀, CIR₆₀, CIR₁₂₀).

RESULTS

Subjects were aged 8.1-30.0 years and 1.1-24.7 years post-transplant; 44% had prediabetes-27% IGT, 14% IFG, and 3% both. IGT was characterized by insulin hyposecretion, with lower CIR₆₀ and CIR₁₂₀ in IGT than subjects with normal glucose tolerance. Subjects with tacrolimus trough >6 µg/mL at study visit had lower CIR₁₂₀ than those with trough ≤6 µg/mL and those off calcineurin-inhibitors. Mean of tacrolimus troughs preceding the study visit, years since transplant, and rejection episodes were not associated significantly with lower CIR. CIR suppression by tacrolimus was most pronounced >6 years from transplant. Overweight/obese subjects and adolescents who retained normal glucose tolerance had greater CIR than those who were IGT.

CONCLUSION

IGT after pediatric liver transplant is driven by inadequate insulin secretion. It is quite common but not detectable with fasting laboratory values-the screening recommended by current guidelines. Calcineurin inhibitors suppress insulin secretion in these patients in a dose-dependent manner. Given the recent focus on long-term outcomes and immunosuppression withdrawal in these children, longitudinal studies are warranted to investigate whether IGT is reversible with calcineurin inhibitor minimization.

HbA1c and the Prediction of Type 2 Diabetes in Children and Adults

OBJECTIVE

Long-term data validating glycated hemoglobin (HbA_1c) in assessing the risk of type 2 diabetes in children are limited. HbA_1c, fasting plasma glucose (FPG), and 2-h postload plasma glucose (2hPG) concentrations were measured in a longitudinal study of American Indians to determine their utility in predicting incident diabetes, all of which is thought to be type 2 in this population.

RESEARCH DESIGN AND METHODS

Incident diabetes (FPG ≥126 mg/dL [7.0 mmol/L], 2hPG ≥200 mg/dL [11.1 mmol/L], HbA_1c ≥6.5% [8 mmol/mol], or clinical diagnosis) was determined in 2,095 children without diabetes ages 10-19 years monitored through age 39, and in 2,005 adults ages 20-39 monitored through age 59. Areas under the receiver operating characteristic (ROC) curve for HbA_1c, FPG, and 2hPG in predicting diabetes within 10 years were compared.

RESULTS

During long-term follow-up of children and adolescents who did not initially have diabetes, the incidence rate of subsequent diabetes was fourfold (in boys) as high and more than sevenfold (in girls) as high in those with HbA_1c ≥5.7% as in those with HbA_1c ≤5.3%-greater rate ratios than experienced by adults in the same HbA_1c categories. Analyses of ROCs revealed no significant differences between HbA_1c, FPG, and 2hPG in sensitivity and specificity for identifying children and adolescents who later developed diabetes.

CONCLUSIONS

HbA_1c is a useful predictor of diabetes risk in children and can be used to identify prediabetes in children with other type 2 diabetes risk factors with the same predictive value as FPG and 2hPG.

Screening for type 2 diabetes and prediabetes in obese youth: evaluating alternate markers of glycemia - 1,5-anhydroglucitol, fructosamine, and glycated albumin

Hemoglobin A1c (HbA1c) is increasingly performed over the oral glucose tolerance test (OGTT) as the initial screening test for type 2 diabetes in youth. However, the optimal strategy for identifying type 2 diabetes in youth remains controversial. Alternate glycemic markers have been proposed as potentially useful tools for diabetes screening. We examined the relationships among fructosamine (FA), glycated albumin (GA), and 1,5-anhydroglucitol (1,5-AG) with traditional screening tests, HbA1c and OGTT. Youth 10-18 yrs, BMI ≥85th‰, and HbA1c <7.5% had a single visit with measurement of HbA1c, 1,5-AG, FA, GA, and a standard OGTT. Distributions of FA, GA, and 1,5-AG by HbA1c and 2-hour glucose (2hG) categories were compared. Receiver operating characteristic (ROC)-curves were generated to determine the cut points at which alternate markers maximized sensitivity and specificity for predicting prediabetes and diabetes. One hundred and seventeen, 62% female, 59% Hispanic, 22% White, 17% black, median 14.1 yr, and body mass index (BMI) z-score 2.3 participated. Median values of each alternate marker differed significantly between prediabetes and diabetes HbA1c and 2hG categories (p < 0.017). Only GA medians differed (p = 0.006) between normal and prediabetes HbA1c. Area under the receiver operating characteristic curves (ROC-AUCs) for alternate markers as predictors of prediabetes (0.5-0.66) were low; however, alternate marker ROC-AUCs for identifying diabetes (0.82-0.98) were excellent. Although the alternate markers were poor predictors of prediabetes, they all performed well predicting diabetes by 2hG and HbA1c. Whereas the usefulness of these markers for identifying prediabetes is limited, they may be useful in certain scenarios as second line screening tools for diabetes in overweight/obese youth.

Comparing glycemic indicators of prediabetes: a prospective study of obese Latino Youth

OBJECTIVE

One hour (1-hr) glucose during an oral glucose tolerance test (OGTT) is an emerging biomarker for type 2 diabetes. We compared the predictive power of 1-hr glucose to traditional glycemic markers for prospectively identifying prediabetes in youth.

RESEARCH DESIGN AND METHODS

Obese normoglycemic Latino youth (N = 116) were assessed at baseline for glycated hemoglobin (HbA1c), fasting, 1-hr, and 2-hr glucose during an OGTT and were followed for up to 8 yr for the development of prediabetes. Receiver operating characteristic (ROC) curves were used and a multivariable prediction model was developed.

RESULTS

The area under the 1-hr glucose ROC curve was the most powerful predictor of prediabetes over time [0.73, 95% confidence interval (CI) = 0.64-0.83]. However, combining all indicators into a single model was superior to individual marker models (0.77, 95% CI = 0.690.86).

CONCLUSIONS

These results further support the utility of 1-hr glucose during an OGTT as a prospective marker of diabetes risk in youth.

Marked increase in rat red blood cell membrane protein glycosylation by one-month treatment with a cafeteria diet

Background and Objectives. Glucose, an aldose, spontaneously reacts with protein amino acids yielding glycosylated proteins. The compounds may reorganize to produce advanced glycosylation products, which regulatory importance is increasingly being recognized. Protein glycosylation is produced without the direct intervention of enzymes and results in the loss of function. Glycosylated plasma albumin, and glycosylated haemoglobin are currently used as index of mean plasma glucose levels, since higher glucose availability results in higher glycosylation rates. In this study we intended to detect the early changes in blood protein glycosylation elicited by an obesogenic diet. Experimental Design. Since albumin is in constant direct contact with plasma glucose, as are the red blood cell (RBC) membranes, we analyzed their degree or glycosylation in female and male rats, either fed a standard diet or subjected to a hyper-energetic self-selected cafeteria diet for 30 days. This model produces a small increase in basal glycaemia and a significant increase in body fat, leaving the animals in the initial stages of development of metabolic syndrome. We also measured the degree of glycosylation of hemoglobin, and the concentration of glucose in contact with this protein, that within the RBC. Glycosylation was measured by colorimetric estimation of the hydroxymethylfurfural liberated from glycosyl residues by incubation with oxalate. Results. Plasma glucose was higher in cafeteria diet and in male rats, both independent effects. However, there were no significant differences induced by sex or diet in either hemoglobin or plasma proteins. Purified RBC membranes showed a marked effect of diet: higher glycosylation in cafeteria rats, which was more marked in females (not in controls). In any case, the number of glycosyl residues per molecule were higher in hemoglobin than in plasma proteins (after correction for molecular weight). The detected levels of glucose in RBC were lower than those of plasma, even when expressed in molal units, and were practically nil in cafeteria-diet fed rats compared with controls; there was no effect of sex. Conclusions. RBC membrane glycosylation is a sensitive indicator of developing metabolic syndrome-related hyperglycemia, more sensitive than the general measurement of plasma or RBC protein glycosylation. The extensive glycosylation of blood proteins does not seem to be markedly affected by sex; and could be hardly justified from an assumedly sustained plasma hyperglycemia. The low levels of glucose found within RBC, especially in rats under the cafeteria diet, could hardly justify the extensive glycosylation of hemoglobin and the lack of differences with controls, which contained sizeable levels of intracellular glucose. Additional studies are needed to study the dynamics of glucose in vivo in the RBC to understand how such extensive protein glycosylation could take place.

Continuous glucose monitoring and its relationship to hemoglobin A1c and oral glucose tolerance testing in obese and prediabetic youth

CONTEXT

The optimal screening test for diabetes and prediabetes in obese youth is controversial.

OBJECTIVE

We examined whether glycosylated hemoglobin (HbA1c) or the oral glucose tolerance test (OGTT) is a better predictor of free-living glycemia as measured by continuous glucose monitoring (CGM).

DESIGN

This was a cross-sectional study of youth 10-18 years old, body mass index (BMI) 85th percentile or greater, with diabetes risk factors.

SETTING AND PARTICIPANTS

Participants (n = 118) with BMI 85th percentile or greater, not on medications for glucose management, were recruited from primary care and pediatric endocrinology clinics around Denver, Colorado.

INTERVENTION

HbA1c, fasting plasma glucose, and 2-hour glucose were collected and all participants wore a blinded CGM for 72 hours.

MAIN OUTCOME MEASURES

CGM outcomes were determined and descriptive statistics calculated. Performance characteristics at current American Diabetes Association cutpoints were compared with CGM outcomes.

RESULTS

CGM data were successfully collected on 98 obese youth. Those with prediabetes had significantly higher average glucose, area under the curve (AUC), peak glucose, and time greater than 120 and greater than 140 mg/dL (P < .01) on CGM than youth with normal HbA1c or OGTT. HbA1c had a greater magnitude of correlation to CGM average glucose, AUC, and minimum glucose; 2-hour glucose had a greater magnitude of correlation to CGM SD, peak glucose, and time greater than 140 and greater than 200 mg/dL. However, there were no overall differences in the strength comparisons between 2-hour glucose and HbA1c correlations to CGM outcomes.

CONCLUSIONS

In obese youth, HbA1c and 2-hour glucose performed equally well at predicting free-living glycemia on CGM, suggesting that both are valid tests for dysglycemia screening.