Variability of Capillary Plasma Glucose in Healthy Individuals in Repeated 75 g Oral Glucose Tolerance Tests

Abstract

A series of ten 75g oral glucose tolerance tests was carried out on each of 14 apparently healthy subjects. The analytical, intra-individual and inter-individual components of variation were calculated by nested ANOVA following duplicate analyses of capillary plasma glucose under optimal conditions. The analyses met the objectively set analytical goal of CV ≤2·2%. There was considerable intra-individual variation, but no subject was ever classified as diabetic or having impaired glucose tolerance. Recent criteria for interpretation of results must be used since conventional population-based reference values are not adequate. Serial results from an individual must differ by more than 0·7 mmol/L for fasting specimens and at least 1·6 mmol/L for other specimens for a statistically significant ( P ≤ 0·05) change to have occurred.