Odds, risks and appropriate diagnosis of gestational diabetes
The International Association of the Diabetes and Pregnancy Study Groups (IADPSG) diagnostic process and criteria for gestational diabetes mellitus (GDM) are designed to identify women at increased risk of a range of adverse pregnancy outcomes related to maternal hyperglycaemia; in particular, excessive fetal growth and fetal hyperinsulinaemia.1 The relationship between maternal hyperglycaemia and adverse outcomes is continuous, and more than one elevated glucose level from oral glucose tolerance testing equates to higher glucose exposure; however, one elevated glucose value is sufficient to impart a higher risk of pregnancy complications.2
We note with concern the recent article in the Journal by d’Emden, which proposes “a more statistically valid basis for diagnosing GDM”.3 It suggests that the criteria for GDM diagnosis proposed in 2010 by the IADPSG1 would result in up to 50% of women with a single elevated oral glucose tolerance test result being “inappropriately diagnosed with GDM as they do not meet the agreed risk threshold”. We consider these statements to be incorrect and offer the following arguments in rebuttal.
Interpreting odds ratios and confidence intervals
No distinction appears to have been made between “odds” and “risks” in the…