Ruling out coronary artery disease in primary care: development and validation of a simple prediction rule

Background

Chest pain can be caused by various conditions, with life-threatening cardiac disease being of greatest concern. Prediction scores to rule out coronary artery disease have been developed for use in emergency settings. We developed and validated a simple prediction rule for use in primary care.

Methods

We conducted a cross-sectional diagnostic study in 74 primary care practices in Germany. Primary care physicians recruited all consecutive patients who presented with chest pain (n = 1249) and recorded symptoms and findings for each patient (derivation cohort). An independent expert panel reviewed follow-up data obtained at six weeks and six months on symptoms, investigations, hospital admissions and medications to determine the presence or absence of coronary artery disease. Adjusted odds ratios of relevant variables were used to develop a prediction rule. We calculated measures of diagnostic accuracy for different cut-off values for the prediction scores using data derived from another prospective primary care study (validation cohort).

Results

The prediction rule contained five determinants (age/sex, known vascular disease, patient assumes pain is of cardiac origin, pain is worse during exercise, and pain is not reproducible by palpation), with the score ranging from 0 to 5 points. The area under the curve (receiver operating characteristic curve) was 0.87 (95% confidence interval CI] 0.83–0.91) for the derivation cohort and 0.90 (95% CI 0.87–0.93) for the validation cohort. The best overall discrimination was with a cut-off value of 3 (positive result 3–5 points; negative result ≤ 2 points), which had a sensitivity of 87.1% (95% CI 79.9%–94.2%) and a specificity of 80.8% (77.6%–83.9%).

Interpretation

The prediction rule for coronary artery disease in primary care proved to be robust in the validation cohort. It can help to rule out coronary artery disease in patients presenting with chest pain in primary care.Chest pain is common. Studies have shown a lifetime prevalence of 20% to 40% in the general population.¹ Its prevalence in primary care ranges from 0.7% to 2.7% depending on inclusion criteria and country,^2–4 with coronary artery disease being the underlying cause in about 12% of primary care patients.^1,5 General practitioners are challenged to identify serious cardiac disease reliably and also protect patients from unnecessary investigations and hospital admissions. Because electrocardiography and the cardiac troponin test are of limited value in primary care,^6,7 history taking and physical examination remain the main diagnostic tools.Most published studies on the diagnostic accuracy of signs and symptoms for acute coronary events have been conducted in high-prevalence settings such as hospital emergency departments.^8–10 Predictive scores have also been developed for use in emergency departments, mainly for the diagnosis of acute coronary syndromes.^11–13 To what degree these apply in primary care is unknown.^14–16A clinical prediction score to rule out coronary artery disease in general practice has been developed.¹⁷ However, it did not perform well when validated externally. The aim of our study was to develop a simple, valid and usable prediction score based on signs and symptoms to help primary care physicians rule out coronary artery disease in patients presenting with chest pain.