Plasma D-dimer: a useful tool for evaluating suspected pulmonary embolus.

Although ventilation-perfusion lung scanning is widely used in evaluating patients with suspected pulmonary embolus, additional rapid screening tests are needed to supplement scintigraphy in patients in whom the scan is indeterminate or the scan results are discordant with clinical suspicion. D-dimer is a fibrin degradation product which should be elevated in the presence of intravascular coagulation. We prospectively studied patients referred for lung scanning by obtaining a plasma D-dimer latex agglutination assay at the time of the scan. Of 64 patients who had pulmonary angiography to confirm the diagnosis, 16 were positive for pulmonary embolus and only one had a normal D-dimer. The D-dimer was normal in 27 of 48 patients without embolus and elevated in 21. Although an elevated D-dimer level is a nonspecific finding, we conclude that a normal D-dimer is a good negative predictor for pulmonary embolus, with a negative predictive value of 0.97.