The value of clinical features in the diagnosis of acute pulmonary embolism: systematic review and meta-analysis

Background: Clinical assessment of patients with suspected pulmonary embolus (PE) is used to estimate the probability of PE and determine what (if any) diagnostic testing is required. Aim: We aimed to estimate the diagnostic value of individual clinical features used to determine the pre-test probability of acute PE. Design: Systematic review and meta-analysis. Methods: We searched electronic databases (1966 to May 2007) and the bibliographies of retrieved articles for any article that reported the diagnostic performance of clinical features compared to a reference standard diagnostic test in patients with suspected acute pulmonary embolism. Likelihood ratios were calculated for each feature and pooled using a random effects model, as implemented by MetaDiSc statistical software. Results: We identified 18 studies for inclusion with a total of 5997 patients. The most useful features (pooled likelihood ratio) for ruling in PE were syncope (2.38), shock (4.07), thrombophlebitis (2.20), current DVT (2.05), leg swelling (2.11), sudden dyspnoea (1.83), active cancer (1.74), recent surgery (1.63), haemoptysis (1.62) and leg pain (1.60); while the most useful features for ruling out PE were the absence of sudden dyspnoea (0.430), any dyspnoea (0.521) and tachypnea (0.561). All other clinical features had likelihood ratios near to one. Many of the analyses involved pooling results that had significant heterogeneity, so these estimates should be used with caution. Conclusions: Individual clinical features only slightly raise or lower the probability of PE. In isolation, they have limited diagnostic value and none can be used to rule in or rule out PE without further testing.