HbA1c vs FPG and 2-Hour OGTT Glucose in Identifying Dysglycemia in Youth




de la Torre, Alejandro
Huynh, Ngan
Hamilton, Luke
Wilson, Don


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INTRODUCTION In recent years, there has been an increased incidence of pre‑diabetes and type 2 diabetes mellitus in youth 10 years of age and older.1 Dysglycemia has been shown to be a continuous risk factor for cardiovascular disease and thus offers a compelling reason for evidence-based screening and management.2 Current ADA guidelines for the diagnosis and management of pre-diabetes in youth are based upon extrapolation from adult studies and may not be valid in the pediatric population.1, 3 EXPERIMENTAL METHODS To evaluate the utility of HbA1c in identifying dysglycemia in youth, results of the HbA1c, fasting plasma glucose (FPG), and 2-h oral glucose tolerance test (OGTT) were collected retrospectively from a multiethnic cohort of 390 youth seen in a preventive cardiology clinic from 2012 to 2015. Results of the HbA1c were compared to the FPG and 2-h glucose following a standard OGTT. RESULTS Table 1. Comparison between HbA1c and FPG values Table 2. Comparison between HbA1c and OGTT 2-h glucose values Of the patients with a HbA1c DISCUSSION HbA1c is frequently used to identify dysglycemia in at‑risk youth. Although it is a convenient screening tool, the results may be discordant with other measures of dysglycemia. Results from the 2005‑2010 Yale Pathophysiology of Type 2 Diabetes in Obese Youth Study indicate that the optimal A1c threshold for identifying T2DM was 5.8% and that the best predictor of 2-h glucose at a 2-year follow-up was the combination of the subject’s baseline A1c and 2‑h glucose.4 A cross-sectional study compared results of OGTT and HbA1c to measurement of glycemia via continuous glucose monitoring. The OGTT and HbA1c each predicted different patterns of dysglycemia, with the former providing a greater correlation with peak glucose and variability and the latter providing a greater correlation with average and overnight glucose values.5 CONCLUSION Diagnostic tests for pre-diabetes and diabetes in youth are often discrepant. It would appear that HbA1c is a convenient but imperfect screening tool in youth. The cutoff for the different categories of glycemia may need to be modified, and the HbA1c may need to be paired with the OGTT to increase the sensitivity of pre-diabetes screening in at-risk youth. More studies are needed to evaluate diagnostic markers of dysglycemia and effective management of pre-diabetes in this vulnerable population.