Validation of previous prognostic models for thrombosis and exploration of modified models in patients with essential thrombocythemia.

Objective: We examined the prognostic factors to validate previous prognostic models for survival and thrombosis with large-scale data on Japanese patients with essential thrombocythemia (ET). Method: We conducted a study in 352 patients with ET to validate previous prognostic models and search for new prognostic factors. Results: The International Prognostic Score for essential thrombocythemia (IPSET), the conventional risk classification and the International Prognostic Score for thrombosis in essential thrombocythemia (IPSET-T) were confirmed to be reproducible in Japanese patients. However, no significant difference was observed between the low-risk and intermediate-risk categories according to the revised IPSET-T, which does not allow direct comparison of the four risk groups. We reevaluated the risk using a modified revised IPSET-T, which was derived from the revised IPSET-T by scoring the factors as follows: one point for age > 60 years, two points for past history of thrombosis, two points for JAK2 gene mutation-positive; total points of 0 = very low risk, 1 = low risk, 2 = intermediate risk, 3 and above = high risk, with significantly different thrombosis-free survival. Conclusion: The modified revised IPSET-T has been useful for 4-group stratification to predict a population that requires therapeutic intervention, irrespective of the treatment regimens.