SPECT Appropriateness: Does It Matter for Patient Outcomes?
In this issue of Circulation, Doukky et al. report findings from a cohort of 1,511 patients from 11 outpatient community-based practices (20 primary care physicians and 2 cardiologists) in the Chicago metropolitan area. The patients underwent single photon emission computed tomographic myocardial perfusion imaging (SPECT), and were then followed for 27 +/- 10 months for major adverse cardiac events (MACE): death, death or myocardial infarction, and cardiac death or myocardial infarction.1 The SPECT studies were categorized on the basis of the 2009 appropriate use criteria (AUC) as appropriate, uncertain, or inappropriate. The investigators report that 823 patients (54.5%) underwent SPECT that were classified as appropriate or uncertain, and 688 patients (45.5%) underwent SPECT that were classified as inappropriate. In those patients whose SPECT were appropriate or uncertain, abnormal scans were of significant value in predicting MACE with hazard ratios of 3.1-3.7, compared to normal scans. However, in those patients undergoing SPECT classified as inappropriate, abnormal SPECT did not achieve statistical significance in predicting MACE, although the hazard ratios ranged from 2.3 to 11.8. Regardless of SPECT appropriateness, the presence of ischemia on SPECT, reflected in the summed difference score (SDS), predicted subsequent coronary angiography and revascularization. As the investigators indicate, this is the first large study validating the prognostic implications of SPECT AUC, further supporting their clinical utility. In this editorial, we will examine both the internal and external validity of this study to place it in context for evidence-based clinicians.
- Received August 30, 2013.
- Accepted September 4, 2013.