D-dimer, oral anticoagulation, and venous thromboembolism recurrence. 
Venous thromboembolism (VTE) requires prolonged treatment to prevent late recurrences.  However, the optimal duration of vitamin K antagonist (VKA) therapy is still controversial.  More recently, D-dimer (D-d) has emerged as a predictive factor for recurrences.  D-d has been evaluated both during and after VKA treatment.  Some patients with DVT of the lower limbs have persistently high D-d during anticoagulation and this could reflect insufficient anticoagulation despite apparently adequate antithrombotic treatment.  Altered D-d during anticoagulation is more frequent in patients with idiopathic or cancer-associated VTE than in those with secondary VTE.  In subjects with an unprovoked VTE event, the time spent at near normal international normalization ratio (INR) values (< 1.5) during the first 3 months of treatment is associated with higher D-d during and after VKA treatment and with a higher risk for late recurrences.  Moreover, the combination of altered D-d and inherited thrombophilia, and not residual venous obstruction, is associated with a significantly higher hazard ratio for recurrence.  Preliminary results of a management study, the PROLONG study, indicate that subjects with normal D-d at 1 month after VKA withdrawal have a low risk of recurrence, and those with altered D-d have a significantly higher risk and deserve prolonged treatment.