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Using HbA_1c Assay for Diagnosis of Diabetes

Hemoglobin A_1c levels are as accurate as glucose measurements for defining the level of hyperglycemia at which retinopathy begins.

Diagnosing diabetes is difficult, especially in children. Current diagnostic tests — fasting plasma glucose or glucose tolerance — usually require multiple office visits. In an important statement from an International Expert Committee appointed by the American Diabetes Association, the European Association for the Study of Diabetes, and the International Diabetes Federation, committee members call for the adoption of the hemoglobin A_1c (HbA_1c) assay for the diagnosis of diabetes. The committee members note that the statement represents their consensus opinion and not necessarily that of the appointing organizations.

The report reviews changes in recommendations for the diagnosis of diabetes during the past 3 decades and presents data on the reliability and validity of fasting plasma glucose and HbA_1c testing. In 1979, the National Diabetes Data Group provided diagnostic criteria for diabetes based on the distribution of glucose levels. These criteria were used for almost 20 years. In 1997, the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus changed the recommendations to emphasize the relation between glucose levels and the presence of long-term complications (particularly retinopathy) and lowered the fasting plasma glucose level for diagnosing diabetes from 140 mg/dL to 126 mg/dL. 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 subjects with HbA_1c levels <6.5%.

Recommendations of particular relevance to children are as follows:

• Diabetes should be diagnosed when the HbA_1c level is 6.5% and the level is confirmed with a repeat HbA_1c test.
  
• HbA_1c testing is indicated when diabetes is suspected but the child does not have classic symptoms or a casual plasma glucose level >200 mg/dL.
  

Comment: This statement has important implications for medicine. For children with a body mass index 85% and other risk factors for diabetes, an HbA_1c level could easily be obtained. The adoption of the HbA_1c measure as the diagnostic test for diabetes will certainly lead to additional testing, and, I suspect, more children and adolescents with diagnoses of diabetes. Whether this ultimately leads to improved care and prevention of long-term complications of diabetes is far less certain.

— Howard Bauchner, MD

Published in Journal Watch Pediatrics and Adolescent Medicine June 24, 2009

Citation(s):

Nathan DM et al. for the International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care 2009 Jun 5; [e-pub ahead of print]. (http://dx.doi.org/10.2337/dc09-9033)

Reader Remarks:

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• Diabetes-early dx
  Bernard A. Yablin, URMCPeds---Retired, 27 Jun 2009 10:08 AM EST
  If the BMI is more than 25-26,should a lipid profile also be obtained?