Endocrine Abstracts

Introduction: A standard oral glucose tolerance test (OGTT) measures samples at 0, 30, 60, 90, 120 min. Insulin and c-peptide are taken along with blood glucose (BG). Whether samples between baseline and 120 min provide any additional value in detecting children at high risk in clinical practice is not well documented. This audit is looking at the value of doing insulin and c-peptide within 2 h post glucose ingestion in otherwise healthy children seen in Oxford Children’s Hospital from 2006–2011.

Methods: All children who have had OGTT were included. Children previously diagnosed with diabetes (either type 1 or type 2 (T2DM)) were excluded. Insulin resistance (IR) was diagnosed by calculating Homeostatic model assessment (HOMA-IR) index >99th centile for age and sex, impaired glucose tolerance (IGT) by 2hr BG >7.1 mmol/l, T2DM when fasting blood glucose (FBG) ≥7.0 mmol/l, 2 h BG ≥11.1 mmol/l or HbA1C ≥0.6.5%. Children with IR, IGT, T2DM were included in disease group (DG) for analysis. The others were grouped as normal group (NG).

Results: Fifty-three children had OGTT. 82% were obese children (BMI SDS >2 S.D.). Mean age 12.4±4.0 years, 57% were female. 18/53 (34%) had normal OGTT, 25/53 (47%) insulin resistance, 3/53 (6%) IGT, 5/53 (9%) IGT+ IR and 2/53 (4%) were diagnosed with T2DM. Insulin and C-peptide results were statistical different (P<0.001) when comparing results between DG and NG at all-time points. 10/53 (19%) were diagnosed with IGT and T2DM detected by samples at 0 and 120 min.

Conclusion: This study supports the value of undertaking OGTT. However, there was no additional value from samples at 30, 60 and 90 minutes. There was no additional value in measuring C-peptide to aid in the diagnosis of IR, IGT or T2DM. Reducing the number of samples taken during the test significantly reduces the cost of the investigation.