Risk of thrombosis in patients with primary immune thrombocytopenia and antiphospholipid antibodies: A systematic review and meta-analysis

• We carried out a meta-analysis of the risk of thrombosis associated with antiphospholipid antibodies in primary ITP
• The presence of lupus anticoagulant was strongly associated to the occurrence of arterial and venous thrombosis
• Anticardiolipid antibodies were also associated with the occurrence of thrombosis, but the association was weaker
• Further studies are needed to refine the association with anticardiolipid and anti-β2GP1 antibodies

Antiphospholipid antibodies (aPL) are common in ITP, but their role for the occurrence of ITP-related thrombosis is controversial. We performed a systematic review and a meta-analysis to investigate the risk of thrombosis associated with lupus anticoagulant (LA), anticardiolipin (aCL) and anti-β2GP-I antibodies in primary ITP.The literature search was run on Medline, Cochrane and ISI Web of Science from January 1st 1980 to December 31st 2014. Unpublished studies were searched in meeting abstracts. The main analysis assessed the risk of all thromboses (arterial or venous) associated with the presence of LA, aCL or anti-β2GP-I antibodies. Random-effect models were used to calculate odds ratios (OR) and their 95% confidence intervals (CI).Searches in electronic databases retrieved 776 citations. Twelve additional studies from unpublished literature were added. Eventually, 10 cohort studies totalizing 1574 patients were included in the analysis. The pooled OR for the risk of all thromboses associated with LA was 6.11, 95% CI [3.40–10.99]; it was 2.14, 95% CI [1.11–4.12] with aCL. The ORs were similar when stratifying on the type of thrombosis (arterial vs. venous). Only two studies assessed the risk of thrombosis associated with anti-β2GP-I antibody positivity; consequently, no pooled OR was computed for these antibodies.This meta-analysis highly suggests that LA positivity, and to a less extent aCL antibodies, are associated with an enhanced risk of thrombosis in primary ITP patients. Further prospective studies are needed to identify the factors associated with the risk of thrombosis among LA patients before assessing prevention strategies.