To evaluate fasting plasma glucose as a screening test for states of gestational diabetes.
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.
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.
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.