Glycated hemoglobin in fractionated erythrocytes.

Erythrocytes were fractionated, by centrifugation, on the basis of cell density, which is proportional to cell age. Glycated hemoglobin (Hb A1c) in the fractionated cells was measured and compared with the Hb A1c in whole blood and with the fructosamine concentrations in plasma of normal and diabetic subjects. In normal subjects, Hb A1c increased according to the age of the erythrocytes, but hyperbolically rather than linearly, indicating the slow conversion of Hb A to Hb A1c with saturability. The greatest correlation of Hb A1c with plasma fructosamine was in younger middle-aged cells. A subgroup of subjects with impaired glucose tolerance had high Hb A1c in older cells. Hb A1c of the young cells reflects recent glycemic status, for monitoring the initial stage of the treatment of diabetics, whereas Hb A1c of the older middle-aged cells more specifically reflects the longer term glycemic status, for screening and for the long-term monitoring index for treatment of diabetes.