A 2 hr oral glucose tolerance test will identify more women at risk for type 2 diabetes when screening postpartum in gestational diabetics.

Abstract

The CDA 2003 Clinical Practice guidelines recommends screening women with gestational diabetes (GDM) in the first 6 months postpartum for type 2 Diabetes Mellitus (T2DM) with a 2 hour 75 g oral glucose tolerance test (2 hr GTT) as a fasting glucose may lead to under-diagnosis of T2DM (Grade D, consensus) and can not identify impaired glucose tolerance (IGT). We performed a randomized controlled trial evaluating the effect of postal reminders on screening rates in women with GDM. All women from this cohort who completed a 2 hr GTT were included. We determined the rates of impaired fasting glucose (IFG) and T2DM diagnosed by a fasting glucose and IGT and T2DM diagnosed by a 2 hr GTT. Of the 428 patients 156 women completed a 2 hr GTT. 20/156 (12.8%) were diagnosed with IFG, 27/156 (17.3%) were diagnosed with IGT and 4/156 (2.6%) were diagnosed with both. 3/156 (1.9%) women were diagnosed with T2DM by a fasting glucose and 8/156 (5.1%) were diagnosed based on the 2 hr glucose result only. If a two step testing strategy was utilized (i.e. only women with fasting glucose >5.6 mmol/L screened with 2 hr GTT ) 15/27 (56%) of women with IGT and 3/11 (27%) of women with T2DM would be missed.