HbA1c is overtested in many adults with type 2 diabetes, study reports

More than 60% of U.S. adult patients with stable and controlled type 2 diabetes receive too many HbA1c tests, according to a study published online December 11, 2015 in The BMJ. Also, patients who are overtested for HbA1c are also more likely to be overtreated with hypoglycemic drugs despite having their diabetes under control, the researchers reported.  

“More is not always better,” said the study’s lead investigator Rozalina McCoy, MD, primary care physician and endocrinologist at the Mayo Clinic, in Rochester, MN. “And in this case, we see that more is actually less, because patients can be not only burdened by additional tests but also harmed by being prescribed extra medication they may not need.”

In this retrospective analysis, researchers reviewed data for 31,545 adults with type 2 diabetes who did not use insulin, who maintained HbA1c levels of less than 7.0%, and who were not pregnant. The researchers found that 6% of patients had 5 or more HbA1c tests in one year, and 55% had three or four tests in one year.

“Because HbA1c is a measure of average glycemia over three months, more frequent monitoring is also not representative of steady state glycemic control and is generally not clinically informative,” the authors wrote.

Current guidelines indicate that patients with stable, controlled type 2 diabetes should have HbA1c testing only once or twice per year, the researchers noted.

“Potential reasons for more frequent testing include clinical uncertainty; misunderstanding of the nature of the test—that is, not realizing that HbA1c represents a three-month average of glycemic control; or a desire for diagnostic and management thoroughness,” Dr. McCoy said. “Other times, it may be the result of fragmentation of care (more than one unconnected provider); the need to fulfill regulatory demands, such as public reporting of performance metrics; or internal tracking of performance.”

Rates of overtesting were lower among patients who received bundled testing (such as cholesterol, creatinine, and HbA1C tests all in the same day).

The researchers also found that excessive testing increased the odds for patients to be overtreated with one or more hypoglycemic drugs, despite having normal HbA1c levels.

“The implications of such overtreatment needs further work to identify whether it results in direct patient harm, specifically hypoglycemia and other adverse drug reactions, in addition to burden of polypharmacy and increased health care use,” they concluded.