D-dimer levels in combination with residual venous obstruction and the risk of recurrence after anticoagulation withdrawal for a first idiopathic deep vein thrombosis.

We assessed the predictive value of D-dimer levels in combination with residual venous obstruction (RVO) for recurrent venous thromboembolism (VTE) in a prospective cohort of outpatients after oral anticoagulant therapy (OAT) suspension for a first episode of idiopathic proximal deep vein thrombosis of the lower limbs during a 2-year follow-up. Patients (n=400) were enrolled on the day of OAT suspension when RVO was determined by compression ultrasonography (present in 48.6\% of patients). D-dimer (cut-off value: 500 ng/mL) was measured 30+/-10 days afterwards (abnormal in 56.4\% of patients). The overall recurrence rate was 16.7\% (67/400; 95\% confidence intervals - CI -: 13-21 \%). The multivariate hazard ratio (HR) for recurrence was 3.32 (95\% CI: 1.78-6.75; p<0.0001) for abnormal D-dimer compared to normal D-dimer and 1.2 (95\% CI:0.72-2.07; p>0.05) for RVO compared to absent RVO. The recurrence rate was 5.7\% (95\% CI:2-13\%) and 10.4\% (95\% CI:6-18\%), respectively, for normal D-dimer either without or with RVO, 22.9\% (95\% CI: 14-33\%) and 25.9\% (95\% CI: 18-35\%), respectively, for abnormal D-dimer, either without or with RVO. When compared with normal D-dimer without RVO, the multivariate HR for recurrence was similar for abnormal D-dimer either with RVO (4.76 - 95\% CI:1.78-12.8) or without RVO (4.3-95\%:1.56-11.88). Abnormal D-dimer at one month after OAT withdrawal is an independent risk factor for recurrent VTE, while RVO at the time of OAT withdrawal, either with normal or abnormal D-dimer after one month, does not influence the risk of recurrence.