| Summary: | Objective As the mortality and rate of obstructive coronary artery disease (CAD) is low in patients with unstable angina (UA), better pre-test selection criteria for acute coronary angiography (CAG) is warranted. We aimed to validate the current guidelines against other clinical variables as predictors of obstructive CAD in UA patients referred for acute CAG. Methods From 2005 to 2012, all CAGs performed at the University Hospital of North Norway, the sole provider of CAG in the region, were recorded in a registry. We included 979 admissions of UA in the primary catchment area to enable retrospective collection from patient hospital records. Obstructive CAD was defined as ≥50% stenosis and considered prognostically significant if found in the left main stem, proximal LAD or in all three main coronary arteries. Characteristics were analysed by logistic regression analysis. A score was developed using odds ratios from significant factors in a multivariable model. Results The overall rate of obstructive CAD was 45%, and the rate of prognostically significant CAD was 11%. The ACC/AHA and ESC guidelines had an area under the curve (AUC) of 0.58. Adding clinical information increased the AUC to 0.77 (95% CI 0.74-0.80). Applying the derived score, we found that 56% (n=546) of patients with a score of <13 had a negative predictive value of 95% for prognostic obstructive CAD. Conclusions CAG can be postponed or cancelled in up to 56% of UA patients, by improving pre-test selection criteria with the addition of clinical parameters to current guidelines.
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