A significant increase in the prevalence of GDM is expected with new IADPSG diagnostic criteria. This new criteria will place greater emphasis on the fasting and 1-hr BSL post 75 g OGTT. It is unclear whether OGTT readings can anticipate treatment requirements.
To evaluate whether (a) fasting, 1-hr or 2-hr BSL predicted the need for insulin therapy and (b) the proposed IADPSG criteria will change GDM prevalence and proportion of women requiring insulin in a multi-ethnicity clinic.
A retrospective cross-sectional study evaluating BSLs post OGTT in women diagnosed with GDM according to ADIPS consensus criteria and then re-evaluation using IADPSG criteria. Only women with a fasting, 1-hr and 2-hr BSL were included. Data were sorted based on GDM treatment.
There were 399 women diagnosed using ADIPS criteria. 307 of these women would be diagnosed based on IADPSG criteria. The fasting (p<0.001), 1-hr (p<0.001) and 2-hr (p<0.029) BSLs differed significantly between treatment groups, however all predicted the requirement for insulin.
ADIPS criteria: 33.6% required insulin. 85.7% were diagnosed based on an elevated 2 hr BSL and within this group 27.2% required insulin. In contrast, of those who had an abnormal fasting BSL , 71.9% required insulin.
IADPSG criteria: 41.4% required insulin. 63.2% were diagnosed on elevated 1-hr +/or 2-hr BSLs and within this group 30.4% required insulin, as opposed to 69.9% of those with an elevated fasting BSL.
23% less women would be diagnosed with GDM based on IADPSG criteria possibly due to a significant proportion of our cohort being of Asian ethnicity. However, this may underestimate the true prevalence as women diagnosed on IADPSG but not ADIPS criteria have not been included. The need for insulin was similar using both diagnostic criteria. Insulin therapy use appeared to be better predicted by fasting BSL excursions which may help guide which patients require tertiary centre referral.