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Early-pregnancy glucose screening for gestational diabetes mellitus
Gerard G Nahum1, Stephen B Wilson, Harold Stanislaw
1Departments of Obstetrics and Gynecology, Duke University School of Medicine, Durham, North Carolina, USA. nahum001@mc.duke.edu
Objective:
To determine the accuracy of the 50-g, one-hour glucose screening test administered at 16 weeks of pregnancy for identifying women with gestational diabetes mellitus.
Study Design:
Two hundred fifty-five women underwent 50-g, one-hour glucose screening tests at 16 weeks of pregnancy. Those with results > or = 135 mg/dL underwent 100-g, three-hour glucose tolerance tests. All patients without diagnoses of gestational diabetes during the second trimester of pregnancy underwent standard third-trimester glucose testing.
Results:
Gestational diabetes mellitus was diagnosed in 25 patients. Glucose screening tests administered at 16 weeks of pregnancy identified 96% (24) of these patients. Patients with 16-week glucose screening test results > or = 135 mg/dL had a 55% risk of developing diabetes during pregnancy, while the risk was 0.6% for patients with 16-week test results < or = 110 mg/dL. Patients with 16-week glucose screening test results in the intermediate range, 111-134 mg/dL, had a 4.8% risk of developing diabetes during pregnancy.
Conclusion:
Glucose screening at 16 weeks of pregnancy is a useful alternative to third-trimester screening for gestational diabetes. The negative predictive value of screening test results < or = 110 mg/dL is 99.4%. The positive predictive value for screening test results > or = 135 mg/dL is 55%. This latter finding is superior to the 8.6-22% found during the third-trimester.