Thromboembolism in patients with immune thrombocytopenia (ITP): a meta-analysis of observational studies.

This meta-analysis describes the incidence rate of arterial and venous thromboembolism (ATE and VTE) in patients with immune thrombocytopenia (ITP), and the relative risk of ATE and VTE in patients with ITP and comparable populations without ITP. MEDLINE and EMBASE were systematically searched for observational studies reporting incidence rates of ATE and VTE in populations with and without ITP between 1996 and 2013 [follow-up completed before thrombopoietin receptor (TPOr) agonists were commercially available]. Three large, population-based studies were identified from Denmark, the United Kingdom, and the United States. The incidence of ATE per 100 patient-years among patients with ITP ranged from 1.0 to 2.8, and among populations without ITP ranged from 0.7 to 1.8; the summary relative risk adjusted for matching factors (aRR) was 1.5 [95 % confidence interval (CI) 1.3, 1.8]. The incidence of VTE per 100 patient-years among patients with ITP ranged from 0.4 to 0.7, and among populations without ITP ranged from 0.1 to 0.4; the summary aRR (95 % CI) was 1.9 (1.4, 2.7). The risk of ATE and VTE among patients with ITP, based on evidence from three large, population-based observational studies, should be considered when evaluating the risk of thromboembolism attributed to ITP treatments, such as TPOr agonists.