Monitoring metabolic control in diabetic outpatients with glycosylated hemoglobin.

The usefulness of HbA, as a monitor of metabolic control was studied in 15 diabetic outpatients during periods of stable, deteriorating, and improving control. Mean fasting concentrations of HbA, and plasma glucose during a 3-month period of stable control were 12.6% +/- 0.8% and 120 +/- 8 mg/dL, respectively. One week after discontinuation of oral hypoglycemic therapy, blood glucose had risen to 172 +/- 23 mg/dL and HbA, to 14.1% +/- 0.7% (P less than 0.025). Reinstitution of therapy resulted in a significant fall of blood glucose within 2 weeks. A significant decline in HbA1 (from 15.3% +/- 0.8% to 14.1% +/- 0.9%, P less than 0.025) occurred 2 weeks later. The data show that the rate of formation of HbA1 is considerably faster than its rate of disappearance. Thus, HbA1 is likely to reflect disproportionally recent episodes of poor control. We conclude that HbA1 is useful to monitor diabetic outpatients during periods of stable and rapidly deteriorating control but is not suited to detect rapid metabolic improvements.