To investigate whether erythrocyte creatine can serve as a corrective index for HbA1c in patients with a shortened mean age of erythrocytes.
HbA1c and creatine in density-fractionated erythrocytes from 18 normal subjects were measured. HbA1c and erythrocyte creatine in the whole blood of 43 patients with liver cirrhosis (LC), 14 patients with hemolytic anemia (HA), 38 other patients with high reticulocyte counts (HRC) (>2.2%), and 59 normal subjects were also measured. The patients in this study all had normal blood glucose levels. A correction formula derived from the linear regression equation for the correlation between HbA1c and erythrocyte creatine was used to correct the patients' HbA1c values.
Among density-fractionated erythrocytes, the young cells exhibited low HbA1c and high creatine values. With progressively increasing density, HbA1c gradually increased and creatine gradually decreased. In the whole blood samples, the HbA1c values were significantly lower (P < 0.001) in LC, HA, and HRC patients than in normal subjects. By contrast, the erythrocyte creatine values were significantly higher (P < 0.001) in LC, HA, and HRC patients than in normal subjects. A linear correlation between HbA1c Cy) and erythrocyte creatine (x) was observed (y = −0.224x + 5.00; n = 154; r = −0.70; P < 0.001). Based on the regression equation, a correction formula was obtained. Low HbA1c values (<4.3%) were found in 24 of the 43 LC patients, 12 of the 14 HA patients, and 20 of the 38 HRC patients. After correction of the HbA1c values, 15 of the 24 LC patients, 9 of the 12 HA patients, and 16 of the 20 HRC patients had HbAlc values within the normal range.
HbA1c decreased in inverse proportion to the increase in erythrocyte creatine because of a shortened mean age of erythrocytes. The abnormally decreased HbA1c value could be assessed with erythrocyte creatine.