Quantitative plasma D-dimer levels among patients undergoing pulmonary angiography for suspected pulmonary embolism.

OBJECTIVE To test the hypothesis that a low D-dimer level has a high negative predictive value for acute pulmonary embolism (PE) among patients undergoing diagnostic pulmonary angiography. DESIGN Blinded comparison of quantitative plasma D-dimer levels, measured using a monoclonal antibody assay, with pulmonary angiographic results from 173 patients with suspected acute PE. SETTING Tertiary care setting at fur participating institutions. PATIENTS Plasma samples were analyzed in 173 patients who underwent diagnostic pulmonary arteriography for suspected acute PE. MAIN OUTCOME MEASURES Sensitivity, specificity, and predictive values of quantitative plasma D-dimer levels for the diagnosis of PE, using pulmonary angiographic data as the criterion standard test. RESULTS Of 35 patients with D-dimer values less than 500 ng/mL, only three had abnormal pulmonary angiograms. The negative predictive value of a plasma D-dimer level less than 500 ng/mL for acute PE was 91.4% (95% confidence interval [CI], 76.9% to 98.2%). D-dimer levels were greater than 500 ng/mL in 42 of 45 patients with PE and in 96 of 128 patients without PE (P = .016). Sensitivity, specificity, and positive predictive value of a plasma D-dimer level greater than 500 ng/mL for acute PE were 93.3% (95% CI, 81.7% to 98.6%), 25.0% (95% CI, 17.5% to 32.5%), and 30.4% (95% CI, 22.8% to 38.1%), respectively. CONCLUSIONS The results of our study indicate that quantitative plasma D-dimer levels can be useful in screening patients with suspected PE who require pulmonary angiography. Plasma D-dimer values less than 500 ng/mL may obviate the need for pulmonary angiography, particularly among medical patients for whom the clinical suspicion of PE is low. The plasma D-dimer value, assayed using a commercially available enzyme-linked immunosorbent assay kit, is a sensitive but nonspecific test for the presence of acute PE.