Fasting plasma glucose performs better than glycated hemoglobin and glycated albumin for diagnosing gestational...

Universal screening for gestational diabetes mellitus (GDM) using the oral glucose tolerance test (OGTT) has been recommended. In resource-poor environments, OGTTs are only administered to high-risk cases. In countries such as South Africa, where female obesity is common, this translates into high numbers of tests. We therefore investigated glycated hemoglobin (HbA1c), glycated albumin (GA) and fasting plasma glucose (FPG) as OGTT alternatives.

This was a cross-sectional study in black South African women between 24 and 32 weeks of gestation who were at high risk for GDM (N = 477). All women underwent an OGTT and were classified as non-GDM or GDM based on the International Association of Diabetes and Pregnancy Study Group (IADPSG) criteria. Demographic and anthropometric data were documented, and blood glucose, GA and HbA1c levels were measured using standardized laboratory procedures. Cut-points for GDM diagnosis using HbA1c and GA were calculated using receiver operating characteristic (ROC) curve analysis.

The sensitivity and specificity of HbA1c at a 5.5% cut-point for GDM diagnosis were 54% and 80% and for GA at a 37.56% cut-point were 54% and 83% whilst FPG at a 5.1 mmol/L (92 mg/dL) cut-point were 87% and 100%, respectively, missing 10 of 78 GDM cases. Applying an FPG cut-point of 4.6 mmol/L (83 mg/dL), nine of the 10 remaining GDM cases were identified, with sensitivity and specificity of 90% and 75%, respectively. This two-tiered approach missed one of 78 GDM cases.

FPG is a viable method for GDM diagnosis that when used in a two-tiered modality reduces the number of required OGTTs by 77%.