ASNC: Nuc appropriateness criteria works, but falters with asymptomatic patients
Educating physicians about appropriate use criteria for ordering SPECT myocardial perfusion imaging resulted in significant changes in referrals, including reduced inappropriate and increased appropriate ordering, according to a poster presentation at the 2010 American Society of Nuclear Cardiology meeting in Philadelphia in September.

In another poster presentation, however, researchers found that strict interpretation of appropriateness criteria for asymptomatic patients without known coronary artery disease (CAD) may fail to detect CAD in a significant proportion of these patients.

In the first study, Terrance S.J. Chua, MBBS, and colleagues from the National Heart Centre in Singapore conducted a review of all consecutive SPECT MPI studies referred to their single tertiary cardiac care center between Feb. 16, 2009 and Aug. 30, 2009.

The study intervention included dissemination of the 2009 American College of Cardiology and ASNC appropriate use criteria (AUC), as well as didactic lectures and discussions about AUC to physicians who were authorized to order SPECT MPI studies.

Researchers found that inappropriate referrals of patients with ischemic equivalent in the nonacute setting declined from 16 percent pre-intervention to 4.3 percent after education. In low-risk patients less likely to have an abnormal MPI, the decline went from 2.7 percent to 1.1 percent. The differences were significant.

Among patients without ischemic equivalent who were referred for the detection of CAD, SPECT use declined from 45.6 percent to 14 percent in the pre- and post-intervention period, respectively, predominantly in low-risk patients (7.1 vs. 3.4 percent) who were less likely to have an abnormal MPI scan. The differences were significant.

However, appropriate referrals for preoperative evaluation of intermediate-risk patients with poor functional class and high-risk patients increased from 7.3 percent to 38.9 percent in the pre- and post-intervention periods, a significant difference, according to researchers.

While Chua and colleagues concluded that the educational effort was effective in changing ordering patterns of referring physicians, they emphasized that the cost effectiveness and clinical implications of these changes require further investigation.

In the second study, Mazhar A. Afaq, MD, and colleagues from the Bay Pines Veterans Affairs Healthcare System in Bay Pines, Fla., focused on AUC that address the detection of CAD and risk assessment in patients who are asymptomatic without ischemic equivalent and with prior test results.

Researchers retrospectively studied 206 consecutive outpatients referred for SPECT MPI from January to February 2009 and identified 23 percent who were asymptomatic and without known CAD.

Applying the 2009 AUC, they found that 43 percent of these imaging studies were appropriate, 43 percent were inappropriate and 12 percent were undetermined. One patient lacked sufficient data to classify.

They further found that 23 percent of appropriate imaging studies had abnormal results. Among the patients with inappropriate studies, 54 percent had interpretable electrocardiograms, 23 percent had prior stress imaging studies done less than two years ago and 23 percent had low coronary heart disease risk. A total of 19 percent of the patients with inappropriate imaging had abnormal results.

Among the patients classified as having undetermined appropriateness, 57 percent had abnormal results and 43 percent had normal results.

Overall, Afaq and colleagues found that one-fourth of outpatients referred for SPECT MPI were asymptomatic and without known CAD at the time of referral. Less than half of these referrals were appropriate according to 2009 AUC.

Approximately one-fifth of imaging studies determined to be inappropriate based on 2009 AUC had abnormal results despite this classification.

Imaging studies that were classified as undetermined yielded almost equal numbers of abnormal and normal results.

"Strictly applying 2009 AUC for SPECT MPI to asymptomatic patients at this VAMC may fail to detect CAD in a significant proportion of these patients," they concluded.