Gestational Diabetes: Use of Glucose Challenge Test as a Diagnostic Test

Abstract

Objective: To evaluate the positive predictive value of 50-g glucose challenge test (50-g GCT) for diagnosis of gestational diabetes (GDM).

Materials and Methods: The study was undertaken at the Faculty of Medicine Vajira Hospital, Navamindradhiraj University by reviewing the medical records of pregnant women who had a 50-g GCT value of ≥ 140 mg/dL followed by a 100-g glucose tolerance test (100-g GTT) between October 2010 and September 2013. Results were classified in 10 mg/dL increments. GDM was diagnosed using Carpenter and Coustan criteria.

Results: The current study included 1,886 cases from universal screening of 9,273 pregnant women. The incidence of GDM was 3.6%. A 50-g GCT cut-off value of ≥ 230 mg/dL provided 95% positive predictive value for diagnosis of GDM with 0.1% probability for overdiagnosis. Among population with positive screening who had at least one risk factor of GDM, a 50-g GCT threshold of ≥ 236 mg/dL could be interpreted as GDM without a false positive case and confirmation by 100-g GTT was not required.

Conclusion: For a policy of universal screening of GDM, a 50-g GCT may be employed as a diagnostic test when the value is ≥ 230 mg/dL.