Original ArticlesDecrease in sensitivity of D-dimer for acute venous thromboembolism after starting anticoagulant therapyCouturaud, F.; Kearon, C.; Bates, S. M.; Ginsberg, J. S.Author Information F. Couturaud, C. Kearon, J.S. Ginsberg and S.M. Bates are with the Hamilton Civic Hospitals Research Centre, and McMaster University, Hamilton, Ontario, Canada. (Received 28 September 2001; revised 2 January 2002; accepted 3 January 2002) Address correspondence to Dr Clive Kearon, McMaster Medical Unit, Henderson General Hospital, 711 Concession Street, Hamilton, Ontario, Canada L8V 1C3. Tel: (+1) 905 383 2251; fax: (+1) 905 575 7320; e-mail: firstname.lastname@example.org Blood Coagulation & Fibrinolysis: April 2002 - Volume 13 - Issue 3 - p 241-246 Buy Abstract D-Dimer testing is useful for the exclusion of acute venous thromboembolism (VTE). Anticoagulant therapy is expected to reduce D-dimer levels in patients with thrombosis and, consequently, it may not be safe to use D-dimer levels to exclude VTE after anticoagulant therapy has been started. The objectives of this study were to estimate the decrease in D-dimer levels after 24 h of heparin therapy and, applying this estimate to the results of a recent study, to calculate the expected reduction in sensitivity. Using pre-defined criteria, we first performed a literature review to determine whether, and by how much, D-dimer levels decrease within 24 h of starting heparin therapy in patients with acute VTE. Using D-dimer levels that were measured in a prospective study of patients with confirmed deep vein thrombosis and/or pulmonary embolism as baselines, we then determined the change in sensitivity (and specificity) that would result from the fall in D-dimer levels that the literature review suggested would have occurred after 24 h of heparin therapy. On the basis of the literature review, we calculated that mean D-dimer levels decrease by 25%, 24 h after starting heparin therapy in patients with acute VTE. This 25% decrease in D-dimer levels resulted in a decrease in sensitivity from 95.6% (95% confidence interval, 90.0–98.6) to 89.4% (95% confidence interval, 83.7–95.1). There is a decrease in D-dimer levels in patients with acute VTE 24 h after starting heparin therapy that is expected to result in a clinically important drop in sensitivity. © 2002 Lippincott Williams & Wilkins, Inc.