B blood group: A strong risk factor for venous thromboembolism recurrence

Abstract Background Non-O blood group patients are at higher risk of first episode of venous thromboembolism (VTE). However, only little is known about the risk of recurrence according to the blood group. In this study, we aimed to determine the impact of ABO blood group on VTE recurrence. Methods We prospectively recruited 106 consecutive patients with a first documented episode of pulmonary embolism (PE). Patients were followed at least 12 months after anticoagulation discontinuation. The main endpoint was recurrence of symptomatic VTE. Results Data from 100 patients were analyzed. Median follow-up was 28 months [24–34.8]. PE was unprovoked in 48 patients. Mean anticoagulation duration was 5.3 ± 2.2 months. The rate of VTE recurrence was 12.7 per 100 patient-years (30 recurrences). B blood group patients had a 2.7-fold increased risk of VTE recurrence (95%CI 1.1-6.2, p = 0.03). On multivariate analysis, B blood group was the strongest independent predictor of VTE recurrence (Hazard Ratio (HR) 2.6, 95%CI 1.1-6.1, p = 0.04). In contrast, A and AB blood groups were not associated with VTE recurrence. VTE recurrences were less frequent in O blood group compared to non-O patients (HR 0.5, 95%CI 0.2-1.1, p = 0.09). O blood group women had a 5-fold decreased risk of VTE recurrence (HR 0.2, 95%CI 0.1-0.8, p = 0.01). Conclusions Non-O blood groups, beyond being involved in the occurrence of a first VTE event, also contribute to VTE recurrence. B blood group is strongly associated with VTE recurrence, thus high-risk B blood group patients could benefit from long-term anticoagulation therapy after a first VTE event.