Screening for gestational diabetes in a high-risk population.

One hundred eighty-one pregnant Navajo women were screened for gestational diabetes. The 50-g oral glucose screening test was greater than 7.2 mmol/L (130 mg/dL) in 44 of 181 subjects (24.3 percent) and greater than 8.3 mmol/L (150 mg/dL) in 23 of 181 subjects (12.7 percent). The incidence of gestational diabetes in the study population was 6.1 percent of all pregnancies by standard oral glucose tolerance testing. Incidence of gestational diabetes was 9.5 percent in 21 subjects whose screening test was 7.2 to 8.3 mmol/L (130 to 149 mg/dL) and 39.1 percent in 23 subjects whose screening test was 8.3 mmol/L (150 mg/dL) or greater. Using equal to or greater than 7.2 mmol/L (130 mg/dL) of glucose as the definition of an abnormal screening test yielded a 0.80 specificity and a 0.25 positive predictive value, while the cost for each case of gestational diabetes detected was $114. Using equal to or greater than 8.3 mmol/L (150 mg/dL) of glucose as the definition of an abnormal screening test yielded a 0.81 sensitivity, 0.58 specificity, and 0.39 positive predictive value, while the cost for each case of gestational diabetes detected was $106. Logistic regression analyses demonstrated that the screening test was more strongly associated with the diagnoses of gestational diabetes than any other risk factor for gestational diabetes. Universal screening of gestational diabetes is recommended in this high-risk population using equal to or greater than 7.2 mmol/L (130 mg/dL) of glucose as the definition of an abnormal screening test.