Measurement of Glycated Hemoglobin Does Not Aid in Predicting CVD Risk

Determination of levels of glycated hemoglobin (HbA1c) does not aid in identifying individuals at risk of developing cardiovascular disease (CVD) according to a recent study.

HbA1c is a derivative of hemoglobin that is formed nonenzymically by reaction at the N terminus of the protein molecule with glucose. In the normal adult human such derivatives constitute a few percent of the total erythrocyte hemoglobin, the most abundant being hemoglobin A1c, which increases several fold in concentration in diabetes mellitus, and is assayed to monitor control of diabetes. Once a hemoglobin molecule is glycated, it remains that way. A buildup of glycated hemoglobin within the red cell, therefore, reflects the average level of glucose to which the cell has been exposed during its life-cycle. Measuring glycated hemoglobin assesses the effectiveness of therapy by monitoring long-term serum glucose regulation. The HbA1c level is proportional to average blood glucose concentration over the previous four weeks to three months.

The recent HbA1c study was conducted in association with The Emerging Risk Factors Collaboration (ERFC), which has established a central database on over two million participants from more than 125 prospective population-based studies, in which subsets have information on lipid and inflammatory markers, other established risk factors and characteristics, as well as major cardiovascular morbidity and cause-specific mortality. Information on repeat measurements on relevant characteristics has been collected for over 300,000 participants to enable estimation of and adjustment for within-person variability.

In the current study, investigators at the University of Cambridge (United Kingdom) analyzed data from 73 studies involving 294,998 participants to discover whether adding information on HbA1c levels to information about conventional cardiovascular risk factors was associated with improvements in the prediction of CVD risk.

They determined that adding information on levels of HbA1c to conventional CVD risk factors was associated with only slight improvement in risk discrimination. In addition, they found that adding information on HbA1c did not improve the accuracy of probability predictors for patients with and without CVD. "Contrary to recommendations in some guidelines, the current analysis of individual-participant data in almost 300,000 people without known diabetes and CVD at baseline indicates that measurement of HbA1c is not associated with clinically meaningful improvement in assessment of CVD risk," said the authors.

The study was published in the March 2014 issue of Journal of the American Medical Association.

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