Abstract:ObjectiveTo further understand the factors that promote thrombosis in essential thrombocythemia （ET） that were not included in IPSET-thrombosis （International Prognostic Score of Thrombosis for ET）. MethodsA systematic evaluation was conducted on 292 studies by retrieving PubMed，Web of Science, and The Cochrane Library. The incidence and relative risk ratio （RR） of thrombosis in ET patients with different risk factors were calculated. The confidence levels for the outcome were analyzed in combination with RR values and recommendation scores (RS) to find the thrombotic risk factors in ET patients. ResultsOut of 9 risk factors that promoted ET thrombosis, there were 4 factors in IPSET-thrombosis, including history of thrombosis （35.0%, RR=3.30, 95% CI : 2.30-4.75）, JAK2V617F positive （21.0%, RR=2.28, 95%CI : 1.14-4.56）, age over 60 years old （ 22.4% , RR=1.95, 95%CI : 1.17-3.23） and cardiovascular risk factors （17.7%, RR =1.90, 95%CI : 1.08-3.35）. The remaining five risk factors, not listed in IPSET-thrombosis, included monoclonal type of ET based on X-chromosome inactivation pattern （XCIP, 30.6%, RR=4.49, 95% CI: 1.58-12.77）, high JAK2V617F burden （33.9%, RR=3.69, 95%CI: 1.70-7.99）, leukocytosis （18.7%, RR=3.05, 95%CI: 1.81-5.13）, MPL mutation （22.1%, RR=2.40, 95%CI: 1.08-5.33） and splenomegaly （25.6%, RR=1.76, 95%CI：1.29-2.40）. ConclusionAmong the risk factors promoting thrombosis in ET patients, five thrombotic risk factors not included in the IPSET-thrombosis have been identified.