Effect on hemoglobin A₁ of rapid normalization of glycemia with an artificial endocrine pancreas

Six insulin-requiring chronically hyperglycemic diabetic patients underwent glucose control for 72 hours with an artificial endocrine pancreas, the Biostator Glucose Controller. Euglycemia was achieved within 4 hours and was maintained (110 ± 2 mg/dl) thereafter. The concentration of hemoglobin A₁ (HbA₁) was elevated, at 12.5 ± 0.6%, at the initiation of Biostator treatment. Decreases in HbA, of 0.5 ± 0.1% (P<0.01) were observed within 4 hours of Biostator therapy. Over the first 16 hours, the slope of the decrease in HbA₁ was -0.068 ± 0.022% per hour; thereafter, the slope was less steep, -0.018 ± 0.004% per hour (P<0.01). After 72 hours, decreases in HbA₁ of 1.8 ± 0.4% (P<0.01) were observed. The current concept of HbA₁ as an indication of integrated glycemia over weeks and months requires modification to account for a small, rapidly reversible component. Interpretation of the value of HbA₁ when measured by a kit method must take into consideration that small changes in HbA₁ may occur over a few hours as a result of a large and persistent change in glycemia.