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Use of nuclear myocardial perfusion imaging (MPI) declined in a large integrated health care system after reaching a peak in 2006, according to a research letter published in the March 26, 2014, issue of the Journal of the American Medical Association. Substitution of other imaging modalities such as cardiac computed tomography (CT) and stress echocardiography cannot explain the reduction, the authors say.

Researchers led by Edward J. McNulty, MD, of Kaiser Permanente Medical Center (San Francisco, CA), analyzed patient-level data from the clinical databases of Kaiser Permanente Northern California for 2.3 million patients from 2000 to 2011. MPI was used in 302,506 patients at 19 facilities in the database, amassing 23.2 million person-years of follow-up.

Between 2000 and 2006, use of MPI increased by nearly half (41%). Starting in 2006, however, MPI utilization decreased steadily, such that by 2011 use had dropped by 51%.

The degree of decrease between 2006 and 2011 did not differ by sex or revascularization history, but was greater for outpatients than inpatients and for persons younger than 65 years (both P for interaction < 0.001; table 1).

Table 1. Change in MPI Rate per 100,000 Person-Years, 2000-2011

Shift Not Offset by Increases in Other Imaging Modalities

Increased use of other non-invasive imaging technologies cannot account for the reduction in MPI utilization, the authors say. Stress echocardiography use was comparable in 2007 and 2011 with 189 tests/100,000 person-years and 182 tests/100,000 person-years, respectively (P = 0.93). Cardiac CT use increased modestly, from 37 tests/100,000 person-years in 2007 to 73 tests/100,000 person-years in 2011 (P = 0.01), potentially accounting for only 5% of the decline in MPI use.

In an email with TCTMD, Kishore Harjai, MD, of Geisinger Wyoming Valley (Wilkes-Barre, PA), agreed that the “reduction in MPI is not balanced by an increase in other noninvasive tests.” He explained that the results are meaningful because “[they] occurred in a system where financial incentives for ordering more tests can be largely discounted.”

Reassuringly, he noted, from 2006 to 2011, the incidence of MI declined by 27% in the population.

A Win for Appropriate Use Criteria?

“These findings suggest a cause-effect relationship between the publication of appropriate use criteria (AUC) in 2005 and reduction in stress testing starting in 2006,” Dr. Harjai posited. Additionally, “the demographics of the enrollees, the baseline prevalence of cardiovascular risk factors, the frequency of positive stress tests, [and] the characteristics of the employed physicians all could have been instrumental [in influencing the results], but are not described in this brief report.” Thus, he wrote, “it is hard to estimate the relative contribution of each of these factors to reduced utilization of stress tests.”

Though it is difficult to generalize the results from Northern California to the rest of the United States, Dr. Harjai said, “If I had to bet, I would guess that these findings do in fact reflect a nationwide trend related to 3 factors: greater emphasis on AUC, better control of CV risk factors, and reduction in reimbursement for stress testing.”

Dr. Harjai suggested that it is “unlikely that [a] reduction in MPI test frequency had any serious negative consequences,… and it is possible (though not confirmed in this report) that less MPI tests led to fewer ‘unnecessary’ diagnostic caths that often result from false-positive stress tests.”

Furthermore, the authors say, “the substantial reduction in MPI use demonstrates the ability to reduce testing on a large scale with anticipated reductions in health care costs.”

Study Details

Patients were 30 years or older. Use of alternative imaging modalities (eg, cardiac CT and stress echocardiography) was estimated using a referrals database from 2007 to 2011. Age- and sex-adjusted annual rates of MPI tests/100,000 person-years were calculated using direct adjustment methods with 2011 as the reference year. 

• Dr. McNulty reports no relevant conflicts of interest.
• Dr. Harjai is the CEO and co-founder of AUCmonkey.com

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