Long-term assessment of glucose control by haemoglobin-AGE measurement

BACKGROUND: Control of blood glucose is important in reducing both the incidence and the severity of complications in diabetes mellitus. One consequence of long- term hyperglycaemia is the formation and accumulation of advanced glycation end-products (AGEs) on tissue macromolecules. An AGE-modified form of human haemoglobin (Hb-AGE) present at high levels in the red cells of diabetic patients, differs from glucose-derived Amadori product HbA1c in being chemically irreversible and thus persisting for the circulating life of the red cell. We therefore compared Hb- AGE with HbA1c as indicators of long-term blood glucose control.

METHODS: In an open study we measured circulating HbA1c and Hb-AGE concentrations in eight patients with poorly controlled non-insulin-dependent diabetes after a switch to subcutaneous insulin therapy and careful blood glucose monitoring.

RESULTS: After 16 weeks of insulin therapy, the mean HbA1c had decreased from 13.3 (SD 1.2) to 7.3 (0.9)% and the mean Hb-AGE from 12.1 (1.5) to 7.3 (1.3) U/mg Hb. The rate of Hb-AGE decline was 23% slower than that of HbA1c (p=0.044).

INTERPRETATION: The observation that Hb-AGE declines more slowly than HbA1c is consistent with the irreversible nature of the AGE product. Because of this property, Hb-AGE may prove superior to HbA1c as a long-term index of circulating glucose concentrations.