Random capillary whole blood glucose test as a screening test for diabetes mellitus in a middle-aged population

This study was aimed at assessing the adequacy of a random capillary whole blood glucose (RCBG) test as a screening test for diabetes mellitus in a middle-aged (55-year-old) Finnish population. Both the screening test (RCBG) and a standard 2-h oral glucose tolerance test (OGTT) were performed on all the participants according to the WHO criteria. The prevalence based on the 2-h OGTTs was 8.5% (11.7% for men and 6.0% for women). The sensitivity, specificity and predictive values of the screening test for diabetes and the receiver operator characteristic (ROC) curves were studied. The likelihood ratios for diabetes within the test categories were also calculated. When a cut-off point of 6.2 mmol l-1 was used, which proved to be the most appropriate in the present study, the specificity was 92% and the sensitivity 63% (79% for men and 40% for women). The men had much higher sensitivities than the women at all cut-off points, but the specificities were comparable. The present study indicated that the RCBG test could be used as a screening test in a subpopulation with a high prevalence of diabetes and severe hyperglycaemia, but it would be quite insensitive in a subpopulation with a considerable overlap of RCBG values between the diabetic group and the non-diabetic one. It would be inappropriate to use the RCBG test as a routine screening test for diabetes in a general population, particularly among subjects with a known low prevalence of diabetes.