Study objective: To assess the accuracy of a rapid ELISA D-dimer assay for the exclusion of pulmonary embolism (PE) in patients suspected of PE, using pulmonary angiography alone as reference method rather than a diagnostic strategy including lung scintigraphy and leg vein ultrasonography.
Methods: In 342 patients who were examined by pulmonary angiography to diagnose or exclude PE, the accuracy of the quantitative rapid VIDAS D-dimer test for the exclusion of PE was evaluated retrospectively. D-dimer levels were assayed in frozen samples collected during the diagnostic work-up at the time of pulmonary angiography while on treatment with unfractionated heparin for 1-2 days.
Results: Mean plasma D-dimer concentrations were increased in patients with angiographic evidence of PE (P <0.0001). The sensitivity of D-dimer for segmental PE was 98%, its accuracy in excluding segmental PE was 99%, higher than the respective figures for subsegmental PE (76% and 94%; P <0.01, both). For both forms of PE combined the sensitivity was 90% and the negative predictive value 94%.
Discussion: The sensitivity and negative predictive values reported here, are low compared with previous studies using the same rapid ELISA D-dimer assay. This probably reflects an overlooking of mild cases of subsegmental PE in previous studies, although a reduction of D-dimer levels by the heparin pretreatment may have contributed to part of the discrepancy. Prospective studies are needed to clarify this issue.