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 pati ents undergoing diagnostic pulmonary angiography. Design.-Blinded comp arison of quantitative plasma D-dimer levels, measured using a monoclo nal antibody assay, with pulmonary angiographic results from 173 patie nts with suspected acute PE. Setting.-Tertiary care setting at four pa rticipating institutions. Patients.-Plasma samples were analyzed in 17 3 patients who underwent diagnostic pulmonary arteriography for suspec ted acute PE. Main Outcome Measures.-Sensitivity, specificity, and pre dictive values of quantitative plasma D-dimer levels for the diagnosis of PE, using pulmonary angiographic data as the criterion standard te st. Results.-Of 35 patients with D-dimer values less than 500 ng/mL, o nly three had abnormal pulmonary angiograms. The negative predictive v alue 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 wer e 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 le vels 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 medica l patients for whom the clinical suspicion of PE is low. The plasma D- dimer value, assayed using a commercially available enzyme-linked immu nosorbent assay kit, is a sensitive but nonspecific test for the prese nce of acute PE.