A 50-g glucose challenge test: is there any diagnostic cut-off?

To evaluate the diagnostic performance of 50-g glucose challenge test for diagnosis of gestational diabetes.

A retrospective study was conducted by reviewing the medical records of pregnant women who had a 50-g glucose challenge test of 140 mg/dL or higher and followed by a 100-g glucose tolerance test. Results were categorized in 10 mg/dL increments. Gestational diabetes was diagnosed using National Diabetes Data Group criteria.

The present study included 2,226 cases from universal screening of 11,084 pregnant women. The incidence of gestational diabetes was 3.2% (351/11,084). Only 1.6% (6/374) of patients with positive screening results of less than 145 mg/dL had gestational diabetes. All of the 6 women undiagnosed by this threshold were gestational diabetes class A1 and had at least one risk factor Of 1,875 women, seven cases (0.4%) would be over diagnosed as gestational diabetes if 100-g glucose tolerance test was not performed after a result of 50-g glucose challenge test of > or = 250 mg/dL (99.6% specificity, 85.8% negative predictive value, 12.3% sensitivity and 86.0% positive predictive value).

A 50-g glucose challenge test may be used as a diagnostic test when the value is > or = 250 mg/dL. The present data suggested that the value of glucose screening of > or = 145 mg/dL can be used as a threshold for a positive test in the low risk women.