D-dimer testing to determine the duration of anticoagulant therapy

The optimal duration of oral anticoagulation after a first idiopathic venous thromboembolism is uncertain. Recent prospective observational studies show that D-dimer levels have a predictive value for the risk of recurrence. D-dimer testing may help in assessing the individual need for prolonged anticoagulation.

The recently published Prolong study investigated 608 patients with a first unprovoked venous thromboembolism who had received oral anticoagulation for at least 3 months. D-dimer testing was performed 1 month after anticoagulation withdrawal. Patients with normal D-dimer (n = 385) did not resume anticoagulation. Patients with abnormal D-dimer were randomized to resume (n = 103) or not resume (n = 120) anticoagulation. All patients were followed for an average of 1.4 years. Study outcomes occurred in 6.2% of patients with normal D-dimer, and in 15.0% and 2.9% of those with abnormal D-dimer who were allocated to stop or to resume anticoagulation, respectively.

Patients with an abnormal D-dimer measured 1 month from anticoagulation withdrawal have a significant incidence of recurrent venous thromboembolism which is reduced by resumption of anticoagulation. The risk of recurrence in patients with normal D-dimer is significantly lower. D-dimer testing can be used to regulate the duration of anticoagulation.