Performance of recommended screening tests for undiagnosed diabetes and dysglycemia

Abstract

OBJECTIVE - To evaluate the performance, in settings typical of opportunistic and community screening programs, of screening tests currently recommended by the American Diabetes Association (ADA) for detecting undiagnosed diabetes. RESEARCH DESIGN AND METHODS - Volunteers aged ≥20 years without previously diagnosed diabetes (n = 1,471) completed a brief questionnaire and underwent recording of postprandial time and measurement of capillary blood glucose (CBG) with a portable sensor. Participants subsequently underwent a 75-g oral glucose tolerance test; fasting serum glucose (FSG) and 2-h postload serum glucose (2-h SG) concentrations were measured. The screening tests we studied included the ADA risk assessment questionnaire, the recommended CBG cut point of 140 mg/dl, and an alternative CBG cut point of 120 mg/dl. Each screening test was evaluated against several diagnostic criteria for diabetes (FSG ≥ 126 mg/dl, 2-h SG ≥ 200 mg/dl, or either) and dysglycemia (FSG ≥ 110 mg/dl, 2-h SG ≥ 140 mg/dl, or either). RESULTS - Among all participants, 10.7% had undiagnosed diabetes (FSG ≥ 126 or 2-h SG ≥ 200 mg/dl), 52.1% had a positive result on the questionnaire, 9.5% had CBG ≥ 140 mg/dl, and 18.4% had CBG ≥ 120 mg/dl. The questionnaire was 72-78% sensitive and 50-51% specific for the three diabetes diagnostic criteria; CBG ≥ 140 mg/dl was 56-65% sensitive and 95-96% specific, and CBG ≥120 mg/dl was 75-84% sensitive and 86-90% specific. CBG ≥ 120 mg/dl was 44-62% sensitive and 89-90% specific for dysglycemia. CONCLUSIONS - Low specificity may limit the usefulness of the ADA questionnaire. Lowering the cut point for a casual CBG test (e.g., to 120 mg/dl) may improve sensitivity and still provide adequate specificity.