The performance of two rapid quantitative D-dimer assays in 287 patients with clinically suspected pulmonary embolism

Context: Objective tests are necessary for the diagnosis of pulmonary embolism (PE). D-dimer assays have been suggested as useful screening tests to exclude this diagnosis. Objective: To compare the diagnostic accuracy of two rapid quantitative D-dimers in patients with suspected pulmonary embolism. Design: Plasma D-dimer levels were measured using two commercially available assays (Tinaquant® and Vidas®). A strict imaging protocol was used to arrive at a final diagnosis of PE or deep venous thrombosis (DVT). Setting: Multicenter study in six Dutch referral centers. Patients: A total of 287 in- and outpatients with clinically suspected pulmonary embolism. Main outcome measures: Diagnostic accuracy indices for the two assays were calculated and additional receiver-operated characteristics (ROC) analysis was performed. Results: Using the manufacturer's advised cutoff values, the sensitivity and specificity were 88% and 52% for Vidas and 82% and 61% for Tinaquant, respectively. These differences were statistically significant (McNemar, P<0.0001). However, no statistical differences were found between the two assays using ROC analysis (AUC=0.78 for both assays). Conclusions: Both quantitative D-dimer tests had similar diagnostic accuracy; however, at the manufacturer's advised cutoff level, Vidas performed significantly better. Nevertheless, to safely exclude pulmonary embolism, D-dimer assays should be combined with other diagnostic tests.

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