Fasting Plasma Glucose as a Primary Screening Test for the Diagnosis of Gestational Diabetes mellitus

Aim: To see the diagnostic efficacy of fasting plasma glucose (FPG) in respect to OGTT during pregnancy. Materials and Method: In this cross-sectional study, we enrolled 542 pregnant women 18 years or older by consecutive sampling irrespective of gestational age. 75gm three samples OGTT was done and categorized them to either normal glucose tolerance (NGT) or abnormal glucose tolerance (AGT) according to World Health Organization (WHO) 2013 criteria. Results: The sensitivity of FPG with a threshold of 5.1mmol/L was 47.3% among the study subjects, which was very low but specificity was very high (99.7%). However, changing the cut off value to 4.7mmo/L and 4.5mmol/L significantly increased the sensitivity to 64.8% and 73.3% with modestly decreased specificity to 86.2% and 73.2% respectively. In pregnant women with gestational age 24 to 28 weeks, FPG with a threshold of 4.5mmol/L could identify 75% of GDM subjects with specificity 76.8%. Furthermore, it has the highest sensitivity in detecting AGT in all three trimesters (80%, 74.4% and 68%) compared to 4.7mmol/L (80%, 68.9% and 50%) and 5.1 (80%, 47.8% and 30%) in 1st, 2nd and 3rd trimester respectively. FPG had positive correlation with maternal age (r=0.138, p=0.001), BMI (r=0.164, p<0.001) but negative correlation with weeks of gestation (r= -0.242, p<0.001). Conclusion: FPG with cut off value of 4.5mmol/L may be used as an initial screening test for GDM to reduce the need for OGTT. Keyword: Gestational Diabetes mellitus, Fasting Plasma Glucose, Screening Test.