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 four 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.