Power of Contemporary Clinical Strategies to Detect Patients with Obstructive Coronary Artery Disease

Abstract

Background: Non-invasive Ischemia Testing (NIST) is recommended for most patients suspected to have stable coronary artery disease (CAD) before invasive cardiac angiography (ICA). We sought to assess the diagnostic predictive ability of NIST over clinical risk profiling in a contemporary sample of patients undergoing the currently recommended diagnostic triage strategy. Methods and results: From 2006 - 2011, 2600 consecutive patients without known CAD undergoing elective ICA in a single tertiary - care centre were retrospectively identified and the prevalence of obstructive CAD determined. To understand the incremental value of frequently used clinical parameters in predicting obstructive CAD, receiver - operating - characteristic curves were plotted for six sequential models starting with Framingham risk score and then progressively adding multiple clinical factors and finally NIST results. At ICA 1268 patients (48.8%) had obstructive. The vast majority (85%) were classified in an intermediate clinical pre - test probability of CAD and NIST prior to ICA was used in 86% of the cohort. The most powerful correlate of obstructive CAD was the presence of severe angina (OR = 9.1, 95% confidence interval (CI), 4.3 - 19.1). Accordingly, the incorporation of NIST in a sequential model had no significant effect on the predictive ability over that achieved by clinical and symptomatic status model (C - statistic 0.754; 95% CI, 0.732 - 0.776, p = 0.28). Conclusions: Less than half the patients with suspect stable obstructive CAD referred to a tertiary level centre for elective ICA had the diagnosis confirmed. In this clinical setting, the results of NIST may not have the power to change the discriminative ability over clinical judgment alone.