Diagnosis of left ventricular systolic dysfunction (LVSD): development and validation of a clinical prediction rule in primary care.

BACKGROUND: Diagnosing suspected left ventricular systolic dysfunction (LVSD) in the community is a challenge for GPs. We developed and validated a clinical prediction rule (CPR) for LVSD based on history, examination and electrocardiogram (ECG).
METHODS: Prospective cohort studies of 458 symptomatic patients (derivation cohort) and 535 patients (validation cohort) in 26 general practices in Tayside and Fife, Scotland. All patients underwent a structured clinical examination and ECG and the 'reference standard' investigation of echocardiography to establish the presence of LVSD.
RESULTS: Four elements from the clinical history and examination were all independently associated with LVSD--male sex [adjusted odds ratio (OR) 2.5; 95% CI 1.1, 5.0], presence of orthopnoea (OR 5.4; 1.9, 13.8) history of myocardial infarction (OR 5.6; 2.3, 13.6) and elevated jugular venous pulsations (OR 15.1; 4.6, 49.3). Addition of ECG (OR 20.6; 2.7, 158.6) provides important diagnostic information in terms of probability of LVSD. A CPR based on the presence or absence of these five elements will generate probabilities ranging from 1% to 97% for LVSD when applied to an individual patient. In the validation cohort, the model under-predicted the probability of LVSD, particularly at lower levels of expected risk, reflecting differences in the risk-factor profiles of the derivation and validation cohorts.
CONCLUSIONS: The derived CPR provides quantitative estimates of post-test probability for LVSD. This rule requires further validation in other populations and settings because of the difficulties encountered in the validation cohort.