Fasting plasma glucose is a useful test for the detection of gestational diabetes

Abstract

OBJECTIVE - To evaluate fasting plasma glucose as a screening test for states of gestational diabetes. RESEARCH DESIGN AND METHODS - Baseline data of a cohort conducted in general prenatal care units in Brazil, enrolling 5,579 women aged ≤20 years with gestational ages of 24-28 weeks at the time of testing and no previous diagnosis of diabetes. A standardized 2-h 75-g oral glucose tolerance test was performed in 5,010 women. Gestational diabetes and its subcategories - diabetes and impaired glucose tolerance - were defined according to the 1994 World Health Organization panel recommendations. We evaluated screening properties of calculated sensitivity and specificity for fasting plasma glucose with receiver operator characteristic curves. RESULTS - For detection of the subcategory diabetes, a fasting plasma glucose of 89 mg/dl jointly maximizes sensitivity (88%) and specificity (78%), identifying 22% of the women as test-positive. For detection of impaired glucose tolerance, a value of 85 mg/dl jointly maximizes sensitivity and specificity (68%), identifying as test-positive 35% of the women. Lowering the cut point to 81 mg/dl increases sensitivity to 81%, but decreases specificity to 54%, labeling as test-positive 49% of the women. CONCLUSIONS - Fasting plasma glucose is a useful test for the screening of both subcategories of gestational diabetes, a threshold of 85 mg/dl being an acceptable option. Effective screening for the subcategory diabetes can be achieved using a cut point of 89 mg/dl. If greater emphasis is placed on the detection of impaired glucose tolerance, a lower value, 81 mg/dl, may be needed.