Hemoglobin AIc as an indicator of the degree of glucose intolerance in diabetes.

Hemoglobin AIc concentration, fasting blood sugar, response to an oral glucose tolerance test, and skeletal muscle capillary basement membrane thickness were measured in diabetic patients. Hemoglobin AIc concentration correlates with both response to a glucose tolerance test (r = 0.82, p less than 0.001) and fasting blood sugar (r = 0.62, p less than 0.001). The correlation of hemoglobin AIc concentration with glucose tolerance is independent of fasting blood sugar concentration (partial r = 0.61, p less than 0.005), whereas that of hemoglobin AIc with fasting blood sugar probably reflects the relationship between fasting blood sugar levels and glucose tolerance (partial r = 0.22, p less than 0.05). Hemoglobin AIc levels do not correlate with basement membrane thickness ( r = 0.15, p less than 0.05).