Can Fasting Blood Sugar be Used as an Indicator of Long-Term Diabetic Control Instead of Estimated Average Glucose?

Labile glycated hemoglobin: an underestimated laboratory marker of short term glycemia

OBJECTIVES

Diabetes mellitus is a major public health problem. Hemoglobin A_1c (HbA_1c) is a key laboratory parameter in the management of diabetes patients. However, in diabetes monitoring, interpretation of HbA_1c results is hampered by the important interindividual variation in red blood cell (RBC) life span. Furthermore, HbA_1c only slowly responds to changes in glucose metabolism. Besides HbA_1c, there exists a labile HbA_1c fraction (l-HbA_1c), exhibiting much faster kinetics. As both HbA_1c and l-HbA_1c are measured by modern standard chromatography, we explored the possibilities of using the l-HbA_1c fraction for monitoring glycemia.

METHODS

l-HbA_1c and HbA_1c fractions were simultaneously assayed on a Tosoh G8 analyzer and expressed as %. l-HbA_1c results were compared with serum glucose and HbA_1c. Concomitantly, RBC distribution width (RDW) was determined on a Sysmex SN analyzer as a marker for erythrocyte life span.

RESULTS

l-HbA_1c could be measured with between-run coefficient of variations (CVs) between 2.2 and 2.3%. l-HbA_1c correlated with both glycemia (r=0.80) and HbA_1c results (r=0.73). In a multiple regression model (r²=0.752), glycemia and HbA_1c were the most determining factors. To a lesser extent, RDW correlated with l-HbA_1c (r=0.158). Furthermore, the l-HbA_1c/HbA_1c ratio weakly positively correlated with RDW (r=0.247).

CONCLUSIONS

L-HBA_1c represents an additional marker for monitoring the rapid occurrence of glycemic disorders that escape detection when using only HbA_1c and blood glucose. RDW can be used as an indicator of atypical RBCs life span, in which the l-HbA_1c fraction may be helpful.