A review of maturity onset diabetes of the young (MODY) and challenges in the management of glucokinase-MODY

To the Editor:

We note with interest the recent review of challenges in the management of maturity onset diabetes of the young associated with glucokinase gene mutations (GCK-MODY).1 In Box 2, Bishay and Greenfield reported a prevalence of gestational diabetes mellitus (GDM) of 5–10%. Indeed, in 2010 we reported an estimated prevalence of 10–11% of GDM in south-western Sydney;2 however, the prevalence is now almost double that figure (18.5% of births at Bankstown-Lidcombe hospital in 2015).

Bishay and Greenfield also summarised the findings of Chakera and colleagues3 for a population of predominantly European descent:

In contrast, in our recent study of women with GDM, we found that at least 8.1 women would need to be tested to identify one case of GCK-MODY.4 Given our interest in the management of women with GDM, we sought to determine whether these criteria were applicable in a large multi-ethnic cohort of women with GDM. Analysing de-identified, prospectively collected data from all women with GDM in our ethnically diverse population, diagnosed using the Australasian Diabetes in Pregnancy Society (1998) criteria at our institution between 1993 and 2013, we categorised the women into two groups: those with body mass index ≤ 21 kg/m² (group A1) and those with body mass index > 21 kg/m² and < 25 kg/m² (group A2). We collected complete data, including post-partum oral glucose tolerance test results, for 171 women (54, group A1; 117, group A2). The oral glucose tolerance test and post-partum glycated haemoglobin results identified few women (< 14%) in either group who still had possible GCK-MODY. Testing all 171 of these women in pregnancy would have been a costly exercise with a low yield. In testing data in different ethnic groups, we therefore recommend caution regarding the number suggested by Chakera and colleagues.