A new warfarin dosing algorithm including VKORC1 3730 G > A polymorphism: comparison with results obtained by other published algorithms

The optimal duration of anticoagulation after recurrent venous thromboembolism(VTE) is poorly established [1,2]. Recent studies suggested that D-dimer may identify patients at low risk of recurrence after a first VTE [3,4]. In a pilot, prospective, cohort study we aimed to assess the negative predictive value of D-dimer in patients with recurrent VTE. Patients with negative D-dimer while on treatment stopped anti coagulation and underwent repeated testing after 7, 15, and 30 days; treatment was resumed if D-dimer turned positive and permanently stopped if it remained negative. The study was interrupted after the enrolment of 75 patients. At that time, treating physicians decided treatment resumption in 12.2% of the patients, but the majority of events were distal or superficial vein thromboses. The rate of objectively documented recurrent proximal deep vein thrombosis (DVT) and/or pulmonary embolism (PE) was 2.56% (95% CI 0.13, 15.07%) in the 39 patients with persistently negative D-dimer at 30 days, for an annual incidence of VTE of 5.65 events/100 patient/years. These preliminary findings suggest that negative D-dimer may identify patients with history of previous VTE at low risk of recurrences, but this approach should be tested in larger trials in highly selected patients.