Training, not self-interest, may prompt inappropriate MPI use

Those who argue that greed and fear drive overuse of myocardial perfusion imaging (MPI) may want to rethink their stance. A study of MPI tests ordered in a center where physicians had no profit motive or likelihood of litigation found rates of inappropriate testing similar to other settings.

In 2009, the American College of Cardiology, the American Society of Nuclear Cardiology and others published revised appropriate use guidelines for cardiac radionuclide imaging. The guidelines are designed to help physicians identify patients who will benefit from studies. Still, average rates of inappropriate use ranged from 10 percent to 15 percent two years later.

David E. Winchester, MD, of the Malcom Randall Veterans Affairs (VA) Medical Center in Gainesville, Fla., and colleagues tested a hypothesis that inappropriate use would be lower than average in a health system such as the VA. Their reasoning was that VA physicians faced neither the financial temptation from self-referral nor significant worries from malpractice. They published their results in a letter in the July 22 issue of JAMA Internal Medicine.

The researchers identified 332 patients in the VA center who received MPI testing between Dec. 1, 2010 and April 11, 2011. Almost half reported a symptom of chest pain. Based on the 2009 appropriate use criteria, 78 percent of the studies were appropriate, 13 percent inappropriate and 8 percent uncertain.

The most common indication of inappropriatenesss was low pretest probability (16.7 percent of the inappropriate group) and patients being asymptomatic for coronary heart disease (also 16.7 percent). Six of nine preoperative MPI tests reviewed were inappropriate.

When Winchester et al analyzed patient characteristics associated with inappropriate use, they found a five-fold higher likelihood with absence of symptoms. Chest pain and diabetes mellitus were associated with a lower likelihood of inappropriate studies.

They found that “a substantial portion of MPI tests were ordered for inappropriate indications.” The lack of a reduction in inappropriate use in the VA setting “suggests a lesser role of defensive medicine and self-referral in the inappropriate use of MPI,” they wrote.

Instead, common influences in medical training may give physicians misperceptions about the benefits of MPI in asymptomatic and low-risk patients. “This exaggerated perception of the benefit would also seem to hold true for preoperative risk assessment, with the majority of preoperative MPI in our study having been inappropriately ordered.”