Can HbA1c and One-Hour Glucose Concentration in Standard OGTT Be Used for Evaluation of Glucose Homeostasis in Childhood?

OBJECTIVE To investigate whether glycosylated hemoglobin (HbA1c) and 1-hour glucose level in oral glucose tolerance test (OGTT) are useful parameters for evaluation of glucose homeostasis in childhood. METHODS The medical records of 106 obese/overweight children aged from 7 to 18 years who underwent OGTT were evaluated retrospectively. The subjects were divided into 2 groups according to their one-hour glucose concentration. Group 1 consisted of subjects whose one-hour glucose level was <155 mg/dL, and Group 2 consisted of subjects whose one-hour glucose level was ≥155 mg/dL. The fasting and 2-hour glucose concentrations of the groups were compared. The sensitivity and specificity levels were determined using the ROC curve to assess the predictive value of HbA1c for impaired glucose tolerance (IGT). RESULTS The mean 2-hour glucose concentration of the subjects in Group 2 was significantly higher than that of the subjects in Group 1 (137.8±35.5 mg/dL versus 113.1±21.2 mg/dL, p<0.05). If a 5.5% cut-off value for HbA1c was accepted as predictor of IGT, the sensitivity was 63% and specificity was 70%. 31% of the subjects with HbA1c levels at or above 5.5% had IGT. This rate was significantly lower in subjects who had HbA1c levels below 5.5% (p<0.05). CONCLUSIONS Obese/overweight children and adolescents whose 1-hour glucose level is ≥155 mg/dL in the standard OGTT carry a high risk for IGT. Obese/overweight children and adolescents whose HbA1c level is at or above 5.5% may have IGT even though their fasting glucose level is normal, thus, OGTT is necessary to evaluate the glucose tolerance.