• Clive Kearon, Frederick A Spencer, Denis O'Keeffe, Sameer Parpia, Sam Schulman, Trevor Baglin, Scott M Stevens, Scott Kaatz, Kenneth A Bauer, James D Douketis, Steven R Lentz, Craig M Kessler, Stephan Moll, Jean M Connors, Jeffrey S Ginsberg, Luciana Spadafora, Jim A Julian, and D-dimer Optimal Duration Study Investigators.
• Ann. Intern. Med. 2015 Jan 6; 162 (1): 27-34.

BackgroundNormal D-dimer levels after withdrawal of anticoagulant therapy are associated with a reduced risk for recurrence in patients with unprovoked venous thromboembolism (VTE) and may justify stopping treatment.ObjectiveTo determine whether patients with a first unprovoked VTE and negative D-dimer test result who stop anticoagulant therapy have a low risk for recurrence.DesignProspective management study with blinded outcome assessment. (ClinicalTrials.gov: NCT00720915).Setting13 university-affiliated clinical centers.Patients410 adults aged 75 years or younger with a first unprovoked proximal deep venous thrombosis or pulmonary embolism who had completed 3 to 7 months of anticoagulant therapy.InterventionAnticoagulant therapy was stopped if D-dimer test results were negative and was not restarted if results were still negative after 1 month.MeasurementsRecurrent VTE during an average follow-up of 2.2 years.ResultsIn 319 patients (78%) who had 2 negative D-dimer results and did not restart anticoagulant therapy, rates of recurrent VTE were 6.7% (95% CI, 4.8% to 9.0%) per patient-year overall (42 of 319), 9.7% (CI, 6.7% to 13.7%) per patient-year in men (33 of 180), 5.4% (CI, 2.5% to 10.2%) per patient-year in women with VTE not associated with estrogen therapy (9 of 81), and 0.0% (CI, 0.0% to 3.0%) per patient-year in women with VTE associated with estrogen therapy (0 of 58) (P = 0.001 for the 3-group comparison).LimitationsImprecision in female subgroups. Results may not be generalizable to different D-dimer assays from the one used in the study.ConclusionThe risk for recurrence in patients with a first unprovoked VTE who have negative D-dimer results is not low enough to justify stopping anticoagulant therapy in men but may be low enough to justify stopping therapy in women.Primary Funding SourceCanadian Institutes of Health Research.

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