Background: Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease in which the platelet count falls to <100 × 109 /L. Corticosteroids are recommended as the first-line treatment, splenectomy is recommended as the second-line treatment, and thrombopoietin receptor agonists (TPO-RAs) and rituximab are recommended as the third-line treatments for ITP in Japanese ITP treatment guidelines. However, in Japan, rituximab is not eligible for reimbursement for the treatment of ITP. The cost-effectiveness of ITP treatment has not been investigated in Japan. Therefore, in this study, the cost-effectiveness of adding rituximab treatment to the existing treatments indicated for ITP in Japan, namely splenectomy and the TPO-RA romiplostim, was investigated based on the scenario that rituximab is eligible for reimbursement in Japan as a treatment for ITP. Methods: The efficacy endpoint was set as the number of years with a platelet count ?30 × 109/L. The analysis was conducted from the healthcare payer's perspective. If the first treatment is ineffective or relapse occurs, then the patient is given the following treatment. The analyzed treatment order consisted of three patterns: Splenectomy-romiplostim (sequence 1), splenectomy-romiplostim-rituximab (sequence 2), and splenectomy-rituximab-romiplostim (sequence 3). A Markov model was built for ITP, and the analysis period was set as 2 years. The discount rate was an annual rate of 2%. Sensitivity analyses of the efficacy of splenectomy, romiplostim, and rituximab; treatment cost; and romiplostim dose were performed. Results: The expected costs per patient over a 2-year period for sequences 1, 2, and 3 were USD 40,980, USD 39,822, and USD 33,551, respectively. The expected years with a platelet count ≤30 × 109/L for the three sequences were 1.75, 1.79, and 1.78 years, respectively. The sensitivity analyses illustrated that the results of the base case analysis were robust. Conclusions: Adding rituximab to standard treatment for ITP (sequences 2-3) is less costly and marginally more effective than standard therapy in adults. According to the study results, if rituximab is reimbursed for the treatment of ITP in Japan, medical expenses are expected to decline.
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