C‐reactive protein and D‐dimer with clinical probability score in the exclusion of pulmonary embolism

Summary This study evaluated the diagnostic value of C-reactive protein (CRP) combined with a clinical decision rule in the exclusion of pulmonary embolism (PE) and compared this with D-dimer. In 363 consecutive outpatients CRP and D-dimer test were performed and clinical probability of PE was assessed. Patients with D-dimer levels <500 μg/l and clinical probability indicating ‘PE unlikely’ were followed for 3 months. Ventilation-perfusion scan or spiral computerized tomography was performed in patients with D-dimer levels ≥500 μg/l or clinical probability indicating ‘PE likely’. The CRP had a sensitivity of 95·7% [95% confidence interval (CI): 90–100] and negative predictive value (NPV) of 98·4% (96–100). CRP <5 mg/l with clinical probability score indicating ‘PE unlikely’ (n = 108, 30%), had a sensitivity of 96·7% (90–100), a specificity of 43·0% (37–49) and NPV of 99·1% (97–100). D-dimer <500 μg/l with clinical probability score indicating ‘PE unlikely’ (n = 170, 51%), had a sensitivity of 96·7% (90–100), a specificity of 67·9% (62–74) and NPV of 99·4% (98–100). Based on retrospective data it was concluded that a standard CRP test can potentially be used to safely exclude PE, either as a sole test or combined with clinical probability assessment. Prospective studies are needed to confirm these findings.