Because half of the people with non-insulin-dependent diabetes mellitus (NIDDM) are undiagnosed and because near-normal glycemic control can prevent diabetic complications, we evaluated the use of field-based random capillary blood glucose measurement as a screening test for NIDDM.
A cross-sectional sample of 828 Egyptians ≥20 years of age underwent both a random capillary blood glucose measurement performed with a portable reflectance meter in the field and an oral glucose tolerance test in the laboratory. The sensitivity and specificity of random capillary blood glucose measurements in predicting the presence of NIDDM were evaluated.
Multivariate analyses showed that the screening test performed better when subjects had eaten shortly before the test (area under receiver operating characteristic curve, 0.87 for a 1-h postprandial period compared with 0.69 for an 8-h postprandial period) and that the optimal capillary blood glucose cutoff points to define a positive test increased with age. For a postprandial period of 1 h, cutoff points of 115 mg/dl for individuals 30 years of age and 140 mg/dl for those 75 years of age yielded similar performance characteristics (sensitivity 82% and specificity 78% for those 30 years old; sensitivity 81% and specificity 80% for those 75 years old).
Adjusting random capillary blood glucose measurements for the postprandial period and using age-specific cutoff point values can improve performance of the screening test.