THE ROC CURVE IN THE EVALUATION OF FASTING CAPILLARY BLOOD-GLUCOSE ASA SCREENING-TEST TOR DIABETES AND IGT

OBJECTIVE - To assess the performance of different cutoff points of fa sting capillary glycemia (FCG) in the diagnosis of diabetes and impair ed glucose tolerance (IGT) using the receiver operating characteristic s (ROC) curve approach. RESEARCH DESIGN AND METHODS- This study includ ed a sample of 4,019 subjects without a previous history of diabetes w ho were recruited for a confirmatory 2-h post-glucose challenge capill ary glycemia from a larger sample of 21,847 individuals screened with FCG. The sensitivity and the specificity of FCG as a screening test we re analyzed in the cutoff range 3.9-8.9 mmol/l, and the corresponding ROC curves were plotted to assess the performance of the lest. RESULTS - The screening test performance was better for diabetes than for IGT in the full range of cutoff points studied. Sensitivities ranged betw een 37.9 and 97.1% for diabetes and 1.8 and 94.4% for IGT; the areas u nder the ROC curves were 0.91 +/- 0.01 and 0.75 +/- 0.01, respectively . The cutoffs showing the best equilibrium between sensitivity and spe cificity approached 5.6 and 5.0 mmol/l for diabetes and IGT, respectiv ely. Factors such as age, color, and family history of diabetes can af fect the screening test performance. CONCLUSIONS - ROC curves can prov ide useful information toward improving the usefulness of FCG as a scr eening test for abnormalities of glucose tolerance.