An expert committee representing 3 leading diabetes organizations has joined forces to recommend the adoption of the hemoglobin A_1C (HgA_1C) assay for the diagnosis of diabetes rather than fasting plasma glucose (FPG). While the HgA_1C assay shows less variability than FPG and requires no overnight fasting, it is 2 to 3 times more expensive than the FPG.

In a report published in Diabetes Care, representatives from the American Diabetes Association (ADA), the International Diabetes Federation (IDF), and the European Association for the Study of Diabetes (EASD) concluded that the HgA_1C assay provides a reliable measure of chronic glycemia and correlates well with the risk of long-term diabetes than a single measure of glucose. They reviewed the evidence linking glycemic exposure with complications and concluded that an HbA_1C of 6.5% should be the diagnostic cutoff and that the diagnosis should be confirmed with a repeat HgA_1C unless clinical symptoms and glucose levels > 200 mg/dL are present. Furthermore, a level ≥ 6% but < 6.5% is sufficient to identify individuals at especially high risk for diabetes.

The recommendations state that using HgA_1C as a diagnostic standard will enable clinicians to more accurately diagnose diabetes, especially in children. Although previous expert committees recommended against using HbA_1C values for the diagnosis of diabetes, the current expert committee concludes that the precision and accuracy of HbA_1C assays have now been shown to be as accurate as glucose measurements at defining the level of hyperglycemia at which retinopathy begins. In a recent analysis, moderate retinopathy was virtually nonexistent among more than 15,000 patients with HbA_1C levels < 6.5%.

HbA_1C is not accurate in cases of severely low hemoglobin; in these cases, the authors recommend that FPG and 2-hour postprandial glucose testing be used. They caution, however, that mixing different methods to diagnose diabetes should be avoided.

The committee members note that the statement represents their consensus opinion and not necessarily that of the appointing organizations.

1. The International Expert Committee. International Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care. 2009;32(7):1-8. Full text available at: http://care.diabetesjournals.org/content/early/2009/06/01/dc09-9033.full.pdf+html. Accessed June 25, 2009.