Venous Thromboembolism In Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis: An Underlying Prothrombotic Condition?

DObjectives. We investigated the incidence and potential underlying risk factors of venous thromboembolism (VTE) in patients with AAV. We assessed haemostatic disturbances and factors that might contribute to the risk of development of VTE.Methods. ANCA-positive AAV patients (n = 187) were included. Previously identified risk factors for VTE and current medication were retrieved from the medical records. We assessed haemostasis using different methods [endogenous thrombin potential (ETP), overall haemostatic potential (OHP), overall coagulation potential (OCP) and overall fibrinolysis potential (OFP)] in patients with active AAV ( n = 19), inactive AAV (n = 15) and healthy controls (n = 15).Results. Twenty-eight VTEs occurred in 24 patients over a total follow-up time of 1020 person-years. A majority of VTEs occurred within the first year after diagnosis. Old age (P<0.01), ongoing prednisolone treatment and recent rituximab administration were more common in the VTE group (P<0.05 for all). ETP and OHP were significantly increased and OFP significantly decreased in plasma from active compared with inactive AAV patients (P<0.05, P<0.01 and P<0.05, respectively) and healthy controls (P<0.001). We could not confirm previously reported risk factors for VTE development.Conclusion. A high prevalence of VTE in AAV patients was seen within the first year after diagnosis, suggesting that disease activity contributes to development of VTE. Old age and concurrent treatment should also be taken into account when estimating VTE risk. The results also indicate disturbances in the haemostatic balance towards pro-thrombotic conditions in AAV patients, where ETP and OHP might be useful markers for identifying patients at high risk.