Objectives: This study aimed to investigate the prevalence and current treatment status of immune thrombocytopenia (ITP) in Taiwan.Methods: This was a retrospective study conducted using claim data collected from the Bureau of National Health Insurance (BNHI) of Taiwan from 2003 to 2007. ITP patients were identified using the ICD-9 code, 287.3 (primary thrombocytopenia), with two diagnoses separated by at least 14 days for diagnostic specificity. In addition, sensitivity analysis was based on 28 (ITP-28) and 84 (ITP-84) days.Results: ITP prevalence ranged from 10.35 to 11.02 (per 100,000 individuals) with an annual number of 2,300 to 2,500 patients, and sensitivity analyses using ITP-28 and ITP-84 criteria showed that the prevalence were "9.52 to 10.35" and "6.87 to 8.14" in 5,445 ITP patients, respectively. The median age of ITP-14 patients was 46.5 years. In children, the female-to-male ratio was nearly equal (0.93), whereas in adults, it was 1.91. About 3.9% received splenectomy, of which 64.3% were responsive to splenectomy. Further, 92.6% were responsive to steroids. The average costs per visit were US$ 36 and US$ 1,700 for outpatients and inpatients, respectively. For steroid-responsive patients, the mean costs for clinic visits and hospitalization were US$ 35 and US$ 1,415, respectively. In contrast, the medical expense for steroid-refractory patients was approximately one and a half times the costs for responsive patients (inpatient: US$ 54; outpatient: US$ 2,349). For splenectomy-responsive inpatients, the average expenses prior to, at, and after splenectomy were US$ 1,877, 5,476, and 2,061, respectively. For splenectomy-refractory inpatients, the costs were comparable to those of responsive patients (P> 0.05). On the contrary, there were significant differences between the expenditure for splenectomy-responsive and -refractory outpatients. Among ITP patients in Taiwan, 7.4% and 6.4% had hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, respectively, and 1.5% had both HBV and HCV infections. Patients with HBV were significantly high in the splenectomy group (splenectomy vs. non-splenectomy 11.7% vs. 7.2%, P = 0.01), and those who were more responsive to splenectomy had a low HCV infection rate, i.e., 14.5% had HCV infection in splenectomy-refractory group vs. 4.38% in splenectomy-responsive group (P = 0.02). Conclusions:The epidemiology of ITP in Taiwan, including the age and sex, was comparable with that in western countries, except with lower incidence of splenectomy in our patients. The status of HBV and HCV infection in splenectomized patients should be closely monitored. The medical expenditure in Taiwan was much lower than that in western countries. We suggest that novel agents or more aggressive treatment strategies should be further explored or considered in Taiwan.