Study Solidifies Role of AUC in SPECT-MPI

When performed in appropriately selected patients, single-photon emission computed-tomography (SPECT) stress myocardial perfusion imaging (MPI) provides high prognostic value, whereas patients "with inappropriate indications receive limited or ineffective risk stratification at high cost and unnecessary radiation exposure," according to a study published Sept. 10 in Circulation .

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The prospective cohort-study looked at 1,511 consecutive patients who underwent an office-based SPECT-MPI study requested by 22 physicians (20 primary care and two cardiologists) from 11 practices in the Chicago metropolitan area. Studies were categorized as appropriate, uncertain or inappropriate based on the 2009 Appropriate Use Criteria (AUC) for Cardiac Radionuclide Imaging.

Results showed that SPECT-MPI referrals were appropriate in 51.6 percent of patients, inappropriate in 45.5 percent and uncertain in 2.9 percent. The incidence of major adverse cardiac events — including death, death or MI, and cardiac death or MI — was significantly higher among patients in the appropriate/uncertain group than in the inappropriate use group. Patients in the appropriate/uncertain group with abnormal SPECT-MPI scans had a multifold increase in the risk of death, cardiac death and other adverse outcomes. Among patients in whom SPECT-MPI was used inappropriately, there was no significant difference in the major adverse cardiac event rates between those with and without abnormal findings.

The authors note that this study was the "first community-based validation of the AUC for MPI" and "was designed and powered to detect incremental prognostic value with appropriate MPI use." In addition, the "incremental risk prediction attained with appropriate use enhanced the excellent prognostic value of MPI in the appropriate/uncertain group; whereas inappropriate use was detrimental to the predictive value of MPI."

They add that the study "further emphasizes the need for optimal patient selection for cardiac testing" and "solidifies [the role of AUC] in clinical practice, policy-making, and reimbursement decisions." Moving forward, there is also a need for "national organizations of primary care and cardiology to educate their members about the AUC," the authors conclude.

Keywords: Uncertainty, Myocardial Perfusion Imaging, Incidence, Death, Patient Selection, Tomography, Emission-Computed, Single-Photon, Cardiology, Chicago, Referral and Consultation, Primary Health Care

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