Glycohemoglobin and glucose tolerance tests compared as indicators of borderline diabetes

We concurrently measured glycohemoglobin and performed 3-h oral (100 g) glucose tolerance tests on 69 ambulatory patients suspected of having abnormal carbohydrate metabolism. The patients were divided into two groups: (a) The 37 patients for whom the results were normal had plasma glucose concentrations of 0.70--1.15 milligram during fasting and 0.70--1.23 g/L 2 h after glucose ingestion. (b) Borderline diabetics exceeded one or both of these limits. The range of glycohemoglobin in the normal group was 3.0--4.7% of total hemoglobin. Of the 21 borderline diabetics, 11 had increased glycohemoglobin (4.8--8.0%). The difference in tolerance test results between borderline diabetics with and without increased glycohemoglobin was insufficient to predict the status of glycohemoglobin. We suggest a tentative definition for latent diabetes: increased glycohemoglobin in the presence of normal or borderline-abnormal glucose concentration in plasma collected during fasting.