Glucose challenge test threshold values in screening for gestational diabetes among black women

Objective The objective of the study was to assess the incidence of gestational diabetes among black women according to various cut-off values of the glucose challenge test. Study design We performed a retrospective chart review of black patients who had a 50-g, 1-hour glucose challenge test between 24 and 28 weeks' gestation of 130 mg/dL or higher followed by a 100-g, 3-hour glucose tolerance test. Results were categorized in 10-mg/dL increments. Gestational diabetes was diagnosed by 2 or more abnormal values using the Carpenter-Coustan criteria. Results The study included 387 patients. The incidence of gestational diabetes diagnosed overall in all patients with a glucose challenge test of 130 mg/dL or higher was 31.2%. The incidence of gestational diabetes in individuals with a challenge test in the range of 130 to 140 mg/dL was 10.7%. The incidence of gestational diabetes with a screening test of 180 mg/dL or higher was 72.0%. Conclusion Our data support the use of 130 mg/dL as the threshold for a positive glucose challenge test and suggest the use of a glucose tolerance test to confirm the diagnosis of gestational diabetes for screening values up to 200 mg/dL.