GCK monogenic diabetes and gestational diabetes: possible diagnosis on clinical grounds

To determine if the previously published clinical criteria for identifying glucokinase monogenic diabetes [GCK gene mutation in maturity-onset diabetes of the young (GCK-MODY)], an elevated antenatal fasting blood glucose of 5.5-8.0 mmol/l, an increment of < 4.6 mmol/l at 2 h in an oral glucose tolerance test and slim are applicable in a large multi-ethnic cohort of women with gestational diabetes.

We analysed de-identified data from all women with gestational diabetes, diagnosed using the Australasian Diabetes in Pregnancy Society (1998) Australian criteria at our institution between 1993 and 2013, making comparisons among those with complete antenatal data including: diagnostic oral glucose tolerance test results meeting the above criteria; pregestational BMI; birth outcomes; and postpartum oral glucose tolerance test data. We categorized these women into two groups: Group A1 had a BMI ≤ 21 kg/m(2) and Group A2 had a BMI > 21 kg/m(2) and < 25 kg/m(2).

Of the 302 women meeting the study entry criteria, we had complete data including a postpartum oral glucose tolerance test result for 171 women: 54 in Group A1 and 117 in Group A2. Ethnicity was significantly different between the groups. The oral glucose tolerance test and postpartum HbA1c results identified few women ( < 14%) in Group A1 and Group A2 who still had 'possible GCK-MODY'.

Our findings indicate that previously recommended clinical criteria for the identification of women likely to have GCK-MODY lack specificity in a cohort of women with multi-ethnic backgrounds. Using these criteria to select women for testing for GCK-MODY in pregnancy would therefore be costly and is likely to yield few women positive for this condition.