Implications of Using Hemoglobin A1C for Diagnosing Diabetes Mellitus
American Journal of Medicine, 05/03/2011
Malkani S et al. – The authors conclude that A1C and plasma glucose tests are frequently discordant for diagnosing diabetes.
- Until 2010, the diagnosis of diabetes mellitus was based solely on glucose concentration, but the American Diabetes Association (ADA) recommendations now include a new criterion: hemoglobin A1C ≥6.5%.
- Because this change may have significant implications for diabetes diagnosis, the authors conducted a comprehensive literature review including peer–reviewed articles not referenced in the ADA report.
- A1C ≥6.5% identifies fewer individuals as having diabetes than glucose–based criteria.
- Convenience of A1C test might increase the number of patients diagnosed, but this is unproven.
- Diagnostic cut–points for both glucose and A1C are based on consensus judgments regarding optimal sensitivity and specificity for the complications of hyperglycemia.
- A1C may not accurately reflect levels of glycemia in some situations, but in comparison with glucose measurements, it has greater analytic stability and less temporal variability.
- When choosing a diagnostic test for diabetes, the limitations of each choice must be understood.
- Clinical judgment and consideration of patient preference are required to appropriately select among the diagnostic alternatives.