Objective: The aim of this study was to evaluate whether fasting laboratory values can predict impaired glucose tolerance (IGT) in adolescents who are at risk for developing type 2 diabetes mellitus (T2DM).
Hypothesis: Elevated fasting triglycerides, a marker for worsening insulin resistance, predict risk for IGT.
Design: Following a fast of at least 9 h, laboratory measures, body mass index (BMI), and demographic information were obtained. The subjects then underwent a 75-g oral glucose challenge with a 2-h postchallenge glucose determination.
Subjects: Eighty-four adolescents aged 12–20 yr with at least two risk factors for developing T2DM (obesity, family history of T2DM, or acanthosis nigricans) and with either a fasting insulin level ≥25 μU/mL or a homeostasis model assessment of insulin resistance (HOMA-IR) ≥3.5 were recruited for the study.
Results: Ten subjects (12%) had IGT [2-h glucose ≥140 mg/dL (7.77 mmol/L)], and 10 subjects (12%) had impaired fasting glucose [IFG; fasting glucose ≥100 mg/dL (5.55 mmol/L)]. However, only three (30%) subjects with IGT had IFG, though all subjects with IGT had a fasting triglyceride level ≥150 mg/dL (1.70 mmol/L). Of those subjects with elevated triglycerides, 29% had IGT. As a screening test to predict risk for IGT, elevated triglycerides >150 mg/dL had a sensitivity of 100% and a specificity of 68%. The positive predictive value was 29%, and the negative predictive value was 100%.
Conclusions: Screening with fasting glucose alone would have missed 70% of subjects with IGT in this population of insulin-resistant adolescents. However, a fasting triglyceride level ≥150 mg/dL was strongly associated with IGT and may help to identify at-risk adolescents who should undergo formal glucose tolerance testing.