The Association Between Pretest Probability of Coronary Artery Disease and Stress Test Utilization and Outcomes in a Chest Pain Observation Unit

Objectives Cardiology consensus guidelines recommend use of the Diamond and Forrester (D&F) score to augment the decision to pursue stress testing. However, recent work has reported no association between pretest probability of coronary artery disease (CAD) as measured by D&F and physician discretion in stress test utilization for inpatients. The author hypothesized that D&F pretest probability would predict the likelihood of acute coronary syndrome (ACS) and a positive stress test and that there would be limited yield to diagnostic testing of patients categorized as low pretest probability by D&F score who are admitted to a chest pain observation unit (CPU). Methods This was a prospective observational cohort study of consecutively admitted CPU patients in a large‐volume academic urban emergency department (ED). Cardiologists rounded on all patients and stress test utilization was driven by their recommendations. Inclusion criteria were as follows: age > 18 years, American Heart Association (AHA) low/intermediate risk, nondynamic electrocardiograms (ECGs), and normal initial troponin I. Exclusion criteria were as follows: age older than 75 years with a history of CAD. A D&F score for likelihood of CAD was calculated on each patient independent of patient care. Based on the D&F score, patients were assigned a priori to low‐, intermediate‐, and high‐risk groups (90%, respectively). ACS was defined by ischemia on stress test, coronary artery occlusion of ≥70% in at least one vessel, or elevations in troponin I consistent with consensus guidelines. A true‐positive stress test was defined by evidence of reversible ischemia and subsequent angiographic evidence of critical stenosis or a discharge diagnosis of ACS. An estimated 3,500 patients would be necessary to have 1% precision around a potential 0.3% event rate in low‐pretest‐probability patients. Categorical comparisons were made using Pearson chi‐square testing. Results A total of 3,552 patients with index visits were enrolled over a 29‐month period. The mean (± standard deviation [SD]) age was 51.3 (±9.3) years. Forty‐nine percent of patients received stress testing. Pretest probability based on D&F score was associated with stress test utilization (p