- Top of page
- Conflict of interest
Summary. 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 full-intensity 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 D-dimer with recurrence was larger among patients with one prior VTE (HR 3.2, 95% CI 1.3–8.0) than in patients with more than one event (HR 1.4, 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. Low-intensity 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.