Gestational diabetes: utility of fasting plasma glucose as a screening test depends on the diagnostic criteria.

AIMS: To demonstrate the effect of diagnostic criteria, as defined by four international expert panels, on the usefulness of fasting plasma glucose (FPG) as a screening test for gestational diabetes mellitus (GDM).

METHODS: We tested 4602 pregnant women using a 75-g oral glucose tolerance test (OGTT) for universal GDM screening. The area under the receiver operating characteristic curve (AUC) was used to determine the FPG performance to detect GDM by the criteria of the American Diabetes Association (ADA), the Australasian Diabetes in Pregnancy Society, the European Association for the Study of Diabetes, and the World Health Organization (WHO).

RESULTS: By applying ADA, Australasian, European and WHO criteria, respectively, the FPG: (i) AUC (95% CI) was 0.882 (0.866-0.897), 0.830 (0.809-0.852), 0.808 (0.791-0.825) and 0.690 (0.670-0.710); (ii) independently could 'rule-in' GDM (with 100% specificity) in 74 (10.9%), 620 (53.5%), 252 (45.3%) and 74 (7.6%) women; (iii) independently could 'rule-out' GDM in an additional 2864 (62.2%), 928 (20.2%), 1510 (32.8%) and 1171 (25.4%) women, at FPG thresholds (with 85% sensitivity); (iv) false-positive rate (FPR) was 29.4, 75.5, 63.8 and 71.2%, at these thresholds.

CONCLUSIONS: The value of the FPG as a screening test for GDM is highly dependent on the diagnostic criteria. The performance is excellent with the ADA criteria. With the other criteria, the high FPR (poor specificity) would limit its utility as a screening test. Regardless of the criteria used, initial testing by FPG can significantly decrease the number of cumbersome OGTTs needed for the diagnosis of GDM.