Background: The aim of this study was to investigate the diagnostic utility of clinical probability, rapid plasma D-dimer assay, compression ultrasonography (CUS) and transthoracic echocardiography (TTE) in patients with suspected pulmonary embolism.
Methods: One hundred forty consecutive outpatients with suspected pulmonary embolism were enrolled in a prospective trial. We evaluated sensitivity, specificity, positive and negative predictive value of a combination of clinical probability, D-dimer, CUS and TTE using perfusion lung scan and pulmonary angiography as a combined gold standard for determining the presence or absence of pulmonary embolism. Clinical probability was assessed in accordance with the PIOPED criteria. The D-dimer (Nycocard) level was considered as abnormal > 0.3 mg/l, the CUS if incompressibility of the leg veins was showed, and the TTE if right ventricular dilation was present, in the absence of chronic pulmonary disease. The combination of these tests was considered consistent with the presence of pulmonary embolism if D-dimer plus CUS and/or TTE showed abnormal results. A pulmonary embolism was excluded if D-dimer and CUS showed normal findings or a low clinical probability was associated with normal findings of CUS and TTE.
Results: One hundred eleven patients were evaluated. Pulmonary embolism was present in 45/111 (40%) patients. The combination of tests showed positive findings in 39/39 patients with pulmonary embolism, negative findings in 47/50 without pulmonary embolism and non-diagnostic results in 22/111 (20%) patients (95% confidence interval--CI 12-28%). There were three false positive and no false negative results. Sensitivity and specificity were 100 and 94% respectively (95% CI 92-100% and 87-100%); positive and negative predictive values were 93 and 100% (95% CI 85-100% and 93-100%). None of these tests, separately, showed enough sensitivity and specificity.
Conclusions: The combination of clinical probability, D-dimer, CUS and TTE was highly accurate to confirm or rule out pulmonary embolism.