D-dimer, factor VIII coagulant activity, low-intensity warfarin and the risk of recurrent venous thromboembolism

Abstract

Background: Elevated plasma D-dimer and factor VIII coagulant activity (FVIIIc)may be associated with the risk of recurrent venous thromboembolism (VTE). Objectives: To evaluate D-dimer and FVIIIc as risk factors for recurrent VTE and assess the efficacy of extended low-intensity warfarin (target International Normalized Ratio 1.5-2.0) in preventing recurrence by biomarker level. Patients and methods: In the Prevention of Recurrent Venous Thromboembolism trial, 508 idiopathic VTE patients treated for ≥ 3 months with fullintensity warfarin, and who had stopped warfarin for 7 weeks on average, were randomized to low-intensity warfarin or placebo and followed for 2.1 years for recurrent VTE. Prerandomization blood samples were analysed for D-dimer and FVIIIc. Results: One-third of participants had elevated baseline D-dimer (≥ 500 ng mL-1) and one-fourth, elevated FVIIIc (≥ 150 IU dL-1). Adjusting for other risk factors, the hazard ratios (HRs) for recurrent VTE with elevated D-dimer or FVIIIc were 2.0 [95% confidence interval (CI) 1.2-3.4] and 1.5 (95% CI 0.8-2.8), respectively. The association of elevated Ddimer with recurrence was larger among patients with one prior VTE (HR3.2, 95% CI 1.3-8.0) than in patients with more than one event (HR1.4, 95%CI 0.7-2.2). For patients with one prior VTE on placebo, the annual recurrence incidence was 10.9% with elevated D-dimer and 2.9% with normal values. Lowintensity warfarin was equally effective in recurrence risk reduction in those with normal or elevated biomarkers. Conclusions: Among patients with idiopathic VTE, measurement of D-dimer, but not FVIIIc, might be useful for risk stratification. The efficacy of extended low-intensity warfarin therapy did not vary by biomarker level. © 2006 International Society on Thrombosis and Haemostasis.