Assessment of long-term glycemia in type I diabetes using multiple blood glucose values stored in a memory-containing reflectometer

The relationship between repetitive hemoglobin A₁ values and daily blood glucose tests performed by 20 insulin-dependent diabetic outpatients was assessed over a six-week period using a modified reflectance meter capable of storing blood glucose determinations automatically. An average of four and a half determinations per subject per day was recorded with a range of average blood glucose values between 82 ± 2 mg/dl and 316 ± 5 mg/dl (mean ± SE). The relationship between average blood glucose and hemoglobin A₁ values was significant when hemoglobin A₁ values at the end of the six-week period were correlated with the mean blood glucose level over that period (r = 0.55, p <0.02), but improved when a more remote hemoglobin A₁ value obtained at 10 weeks was used (r = 0.64, p <0.005). Hemoglobin A₁ values covering two-week intervals were extremely poor in reflecting average glycemia. The average fasting blood glucose level in these subjects was highly correlated with the overall daily blood glucose values (r = 0.89, p <0.0001), although the coefficients of variation of these parameters averaged 43 ± 3 percent and 47 ± 2 percent, respectively, and were greater than that of the hemoglobin A₁ values over six weeks (10 ± 2 percent). It is concluded that labile blood glucose control in patients with insulin-dependent diabetes is accurately reflected by the average fasting blood glucose level, although multiple determinations must be employed. Satisfactory assessment may be made by use of hemoglobin A₁ value provided that the hemoglobin A₁ determination follows a sufficiently long period of time, presumably related to the turnover of glycosylated hemoglobin.