OBJECTIVES: To assess treatment costs per overall platelet response with romiplostim+concurrent treatment vs. placebo+concurrent treatment in chronic adult ITP, from a national payer perspective in Spain. METHODS: Platelet response was defined as a platelet count of ≥50x109/L. Overall platelet response rates to romiplostim and placebo were used for the analysis and derived from two parallel clinical trials in splenectomized and non-splenectomized ITP patients [1]. All patients were allowed to enter on concurrent ITP medication (danazol, corticosteroids, azathioprine) and receive rescue medication (eg, intravenous immunoglogulins). Treatment costs were calculated over the 24-week clinical trial period and included intervention, rescue medication and management of bleeding-related events. Costs were based on the 2009 national reimbursement list. Mean treatment cost per response was calculated for overall population, and for splenectomized and non-splenectomized patients.   RESULTS: Cost per response was substantially lower for romiplostim compared to placebo. Overall response rate was 83% for romiplostim and 7% for placebo (splenectomized patients 79% vs. 0%, non-splenectomized patients 88% vs. 14%, respectively). Mean treatment costs were €15,781 for romiplostim and €8,111 for placebo (splenectomized patients €15,436 vs. €10,263, non-splenectomized patients €16,125 vs. €5,958, respectively). Cost per response with romiplostim was €19,013 compared to €115,871 with placebo (splenectomized patients €19,539 vs. infinite cost/response, non-splenectomized patients €18,324 vs. €42,557, respectively). The main cost-offsets were due to reduced immunoglobulin rescue use. CONCLUSIONS: Romiplostim represents an efficient use of healthcare resources in both splenectomized and non-splenectomized ITP patients for the Spanish healthcare system, leading to a significant improvement in managing a disease with a limited number of existing effective therapies. [1] Kuter et al. Lancet 2008;371:395-403.