Evaluation of glycaemic status in young people with clinical insulin resistance; fasting glucose, fasting insulin or an oral glucose tolerance test?

P>Objective It is important to identify young people with prediabetes for early intervention. However, it is unclear how to best screen overweight and obese young people for prediabetes. The objective of this study was to compare fasting indices with an oral glucose tolerance test (OGTT) in diagnosing prediabetes. Design Retrospective review. Patients A total of 224 young people, aged 12 center dot 0 years (range: 3 center dot 2-17 center dot 3 years), with clinical features of insulin resistance, who had an OGTT between 2000 and 2007 at a tertiary children's hospital, Sydney, Australia. Measurements Oral glucose tolerance test. Results A total of 168 (75%) participants had normal glucose tolerance, 45 (20%) had prediabetes and 11 (5%) had type 2 diabetes; 29 of those with prediabetes and 10 with type 2 diabetes were identified by fasting glucose criteria alone. Young people with normal fasting glucose and fasting insulin < 180 pmol/l had lower insulin resistance (homeostasis model assessment median 1 center dot 9 vs. 4 center dot 2, P < 0 center dot 001), higher insulin sensitivity index (2 center dot 4 vs. 1 center dot 0, P < 0 center dot 001) and a lower early insulin response (insulinogenic index 2 center dot 5 vs. 4 center dot 1, P < 0 center dot 001) compared to those with normal fasting glucose and higher fasting insulin levels. If a fasting insulin cut point (< 180 pmol/l) was used in addition to fasting glucose to determine the need for an OGTT, 114 (68%) young people with normal glucose tolerance would have avoided the test. By contrast, the diagnosis of impaired glucose tolerance, identified by an OGTT, would have been missed in three children. Conclusion Fasting glucose and insulin levels should be measured in young people with insulin resistance before undertaking a time- and resource-intensive OGTT.