Rapid fluctuations in glycohemoglobin (hemoglobin Alc) related to acute changes in glucose

Since glycohemoglobin (Hb Alc) has been observed to change acutely, Hb Alc was studied in both human and monkey subjects to determine whether acute changes occurred with rapid changes in plasma glucose concentration. A marked increase in Hb Alc was observed over 2 days in a 3 1/2-year-old boy who developed steroid-induced diabetes mellitus. In addition, a significant fall in Hb Alc was observed over 7 days in a pregnant woman recovering from hyperglycemia and ketoacidosis. During marked acute hyperglycemia and its recovery, three normal rhesus monkeys were studied for changes in plasma glucose and Hb Alc over 1 day. Hb Alc more than doubled in each study by the time plasma glucose reached approximately 90 mmol/L and then declined by 12 hr. While maintained at their usual stable glucose concentrations, human and monkey subjects showed little differences in Hb Alc levels for dialyzed and nondialyzed hemolysates. With acute changes in blood glucose, however, the dialysis for 48 hr yielded lower Hb Alc values. Hb Alc increased when hemolysates were dialyzed against high glucose concentrations. Thus the effect of dialysis in sample preparation may be an important factor in correlating glycohemoglobin with acute and chronic changes in glucose status.