D-dimer as a risk factor for deep vein thrombosis: the Leiden Thrombophilia Study.

We studied the association of D-dimer with the risk of deep vein thrombosis (DVT). D-dimer was measured in 474 patients more than 6 months after diagnosis of a first DVT and in 474 age- and sex-matched controls. For D-dimer above the 70th percentile (130.5 ng/ml), the odds ratio (OR) for DVT was 2.2 (95% CI, 1.6-2.9). The association was unchanged with adjustment for other risk factors. Excluding participants with Factor V Leiden, prothrombin 20210A, or factors VIIIc or IX above the 90th percentile, the OR was 1.6 (95% CI, 1.1-2.3). The risks of DVT with the joint presence of high D-dimer and either factor V Leiden or prothrombin 20210A were increased 12.4-fold (95% CI 5.6-27.7) and 7.2-fold (95% CI 2.1-25.1), respectively. Higher D-dimer concentration was associated with the risk of DVT, and was supra-additive to the risks associated with factor V Leiden and the prothrombin 20210A variant. Persistence of this association in the absence of other hemostatic risk factors for DVT suggests that high D-dimer may be related to other, as yet unknown, risk factors for venous thrombosis. Confirmation of these findings is desirable.