Glycated Hemoglobin Levels Accurately Predict Risk of Type II Diabetes

A large screening study provided compelling new evidence that the level of HbA1c (glycated hemoglobin) in the blood can accurately gauge diabetes risk at an earlier stage than is currently recognized.

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 American Diabetes Association and the World Health Organization have suggested that an HbA1c level of 6.5% or more is an indicator of type II diabetes and an HbA1c level of between 5.7 and 6.4% is an indicator of prediabetes.

To evaluate the utility of HbA1c screening for type II diabetes in high-risk patients, investigators at the Tel Aviv University Sackler Faculty of Medicine (Israel) evaluated the medical history of 10,201 patients who had been tested for HbA1c in central Israel between 2002 and 2005. They reported that overall, 22.5% of the patients developed diabetes within five to eight years. Patients with HbA1c levels as low as 5.5%—below the official threshold for diagnosing diabetes— were significantly more likely to develop diabetes than patients with HbA1c levels below 5.5%. Every 0.5% increase in HbA1c levels up to 7% doubled the patients' risk of developing diabetes.

"We were actually able to quantify how risk increases with HbA1c levels," said first author Dr. Nataly Lerner, a researcher at the Tel Aviv University Sackler Faculty of Medicine. "This could allow doctors to make more informed decisions regarding diabetes prevention. Our study supports the idea that the HbA1c test, used to diagnose type II diabetes, can also be used at a much earlier stage to screen for the disease in the high risk population, like overweight patients."

The study was published in the November 29, 2013, online edition of the European Journal of General Practice.

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Tel Aviv University Sackler Faculty of Medicine