Incidence of Thrombosis at Different Sites During the Follow-Up Period in Essential Thrombocythemia: A Systematic Review and Meta-Analysis.

Thrombotic events are the most frequent manifestations of essential thrombocythemia (ET). The objective of this study is to determine the incidence of thrombosis at different sites on follow-up in patients with ET. We searched PubMed, Web of Science, and The Cochrane Library databases and calculated the incidence of thrombosis by pooling and analyzing the extracted data using a random-effects model. A total of 70 studies (N  =  25,805) were included in the analysis. The total and annual incidences of arterial thrombosis on follow-up were 13.4% and 2.0%, respectively. The total and annual incidences of the different manifestations of arterial thrombosis were as follows: stroke (5.3% and 0.8%), transient ischemic attack (5.1% and 1.2%), myocardial infarction (2.4% and 0.5%), unstable angina (0.9% and 0.2%), and peripheral arterial thrombosis (2.0% and 0.2%), respectively. In contrast, the total and annual incidences of arterial thrombosis in JAK2-positive patients were 18.4% and 2.7%, respectively. The total and annual incidences of arterial thrombosis in JAK2-negative patients were 5.9% and 0.8%, respectively. The total and annual incidences of venous thrombosis were 5.5% and 0.7%, respectively, and the incidences of the different manifestations of venous thrombosis at different sites were as follows: peripheral venous thrombosis (2.9% and 0.5%), superficial venous thrombosis (1.8% and 0.7%), deep venous thrombosis (1.6% and 0.3%), abdominal venous thrombosis (0.8% and 0.1%), pulmonary embolism (0.3% and 0.1%), and cerebral venous thrombosis (0.2% and 0%), respectively. The total and annual incidences of venous thrombosis in JAK2-positive patients were 7.4% and 1.2%, respectively. The total and annual incidences of venous thrombosis in JAK2-negative patients were 1.6% and 0.4%, respectively. The incidence of arterial thrombosis was higher than that of venous thrombosis in patients with ET. Arterial thrombosis manifested with cerebral arterial thrombosis, followed by cardiac thrombosis. Venous thrombosis events were mainly peripheral and superficial venous thrombosis. JAK2-positive patients have a higher incidence of arterial and venous thromboses than JAK2-negative patients, the sequence of thrombsis sites was similar to that of the overall patients.