Can fasting plasma glucose replace oral glucose-tolerance test for diagnosis of gestational diabetes mellitus?

Background and aims Gestational diabetes mellitus (GDM) has high prevalence worldwide. This study aimed to evaluate the fasting plasma glucose (FPG) cutoffs at first prenatal visit and at 24-28th of gestational weeks to avoid obtaining full oral glucose-tolerance test (OGTT) in the diagnosis of GDM. Methods This study was a cross-sectional study conducted in Tehran, Iran during October 2016 and November 2017. All pregnant women reporting for the first routine prenatal visit before 20th week of gestational age were included in this study. Participants without overt diabetes mellitus at first prenatal visit, underwent OGTT at 24-28th of gestational weeks. Results Totally 952 pregnant women with mean age of 26.4 +/- 14.1 years took part in this study. The prevalence of GDM was 12.7% (mostly diagnosed based on the FPG alone). FPG cutoffs 75 and 80 mg/dL at first prenatal visit and at 24-28th of gestational weeks can rule out the GDM with high sensitivity and negative predictive value, respectively. FPG cutoffs 85 and 90 mg/dL at first prenatal visit and at 24-28th of gestational weeks had high capacity, excellent specificity and positive predictive value in diagnosing GDM, respectively. Conclusions Performing only the FPG and considering FPG cutoffs 75 and 80 mg/dL at first prenatal visit and at 24-28th of gestational weeks can be a useful tool predicting the incidence of GDM, respectively, and had similar diagnostic power.