The American Diabetes Association’s decision earlier this month to officially endorse hemoglobin A1c as a diagnostic test for diabetes is either timely, inappropriate, or long overdue, depending on whom you talk to.
Use of HbA1c for diabetes diagnosis was initially endorsed as a consensus opinion last summer by an international expert committee. The ADA working group reviewed that paper and arrived at similar conclusions (except that ADA did not say HbA1c is the “preferred” test).
“There is an inherent attractiveness to using the A1c, since it measures glucose exposure over a long period of time, not just the specific instance of when the blood test is obtained. … In all, the recent guidelines gives practicing clinicians another tool to screen patients who are at risk for diabetes,” Dr. Inzucchi said.
But Dr. Zachary T. Bloomgarden of Mount Sinai School of Medicine, New York, said ADA’s move is “overall, not to my mind satisfactory.” Although he says he believes HbA1c could be used to screen people who would then undergo further testing, he says its use as a stand-alone diagnostic test could lead to overdiagnosis of “high glycators” or underdiagnosis of “low glycators,” each of whom comprise about 10% of the population.
At the other extreme is Dr. Mayer Davidson of the University of California, Los Angeles, who has been advocating use of the HbA1c to diagnose diabetes for more than a decade. In fact, he says he believes it should be the only test: “Unfortunately, the ADA kept the glucose criteria, which will lead to the confusing situation of people who have diabetes by one criterion but not by the other when both are measured, which is likely to occur frequently.”
So will the new endorsement change clinical practice? In a 2005 survey of 258 internists, 93.4% reported that they routinely screened for diabetes, 49% reported using HbA1c for screening, and 58% said they used it for diagnosis of diabetes. Interestingly, 49% mistakenly thought HbA1c was already an approved screening test (J. Clin. Endocrinol. Metab. 2008;93:2447-53).
–Miriam E. Tucker (@MiriamETucker on Twitter)