Circulating microparticles and risk of venous thromboembolism

Introduction: Circulating microparticles (MPs) may trigger a hypercoagulable state, leading to thrombotic complications. Data on their association with venous thromboembolism (VTE) are few and inconsistent. Materials and methods: To investigate whether or not high levels of MPs are associated with an increased risk of VTE, we carried out a case-control study on 186 patients with a first, objectively diagnosed, episode of VTE and 418 healthy controls. Plasma levels of circulating MPs were measured by flow cytometry. Results: Patients had higher median plasma levels of total MPs than controls (2184 per mu L vs 1769 per mu L, p <0.0001). The risk of VTE increased progressively with increasing MPs, with a linear dose-response effect in the log odds. Individuals with MPs above the 90th percentile of the controls' distribution (P-90 = 3263 per mu L) had a 5-fold increased risk of VTE than those with MPs below the 10th percentile of controls (P-10 = 913 per mu L), independently of sex, age, body mass index, thrombophilia, and plasma factor VIII levels [adjusted odds ratio: 5.30 (95%CI: 2.05-13.7)]. Using the 95th percentile of controls as cut-off (P-95 = 4120 per mu L), the adjusted odds ratio was 2.20 (1.01-4.79) for individuals with MPs > P-95 compared with those having MPs <= P-95. After exclusion of individuals with antiphospholipid antibodies and hyperhomocysteinemia, the interaction between MPs > P-95 and thrombophilia increased the VTE risk from 1.63 (0.60-4.50) to 6.09 (1.03-36.1). Conclusions: High levels of circulating MPs are a possible independent risk factor for VTE. (c) 2011 Elsevier Ltd. All rights reserved.