Evaluation of the Combination of a Bedside D-Dimer Assay and Enzyme-Linked Immunosorbent Soluble Fibrin Assay in Patients with Suspected Venous Thromboembolism

The objectives of the study were to determine whether the combination of a negative SimpliRED D-dimer assay and a low soluble fibrin result reliably excludes venous thromboembolism, and whether patients with proven venous thromboembolism and a normal SimpliRED D-dimer have evidence of impaired fibrinolysis. The study was a retrospective analysis of a cohort of 262 consecutive patients, 94 patients presenting with suspected deep venous thrombosis and 168 with suspected pulmonary embolism. Fifty-nine patients (22.5%) were classified as venous thromboembolism-positive, 27 with pulmonary embolism, and 32 with deep venous thrombosis. One hundred and fourteen patients (43.5%) had SimpliRED D-dimer and a soluble fibrin result of less than or equal to 2.0 microg/ml; the negative predictive value was 98.2% (95% confidence interval: 93.8-99.8%), and the likelihood ratio was 0.06. Eight patients with proven venous thromboembolism had a negative SimpliRED D-dimer; all had elevated ELISA D-dimer levels and six had elevated soluble fibrin levels. This suggests that patients with venous thromboembolism and a normal SimpliRED result do not have impaired fibrinolysis as a cause of their false-negative result. This study suggests that the combination of SimpliRED and soluble fibrin can be used to exclude venous thromboembolism in over 40% of patients who present with a clinical suspicion of deep venous thrombosis or pulmonary embolism and that the small group of patients with venous thromboembolism and a normal SimpliRED do not have impaired fibrinolysis.