Incidence of immune thrombocytopenia in Taiwan: a nationwide population-based study

BACKGROUND: The incidence of immune thrombocytopenia (ITP) is not well known in Asians. The aims of this study were to survey incidences and clinical features of ITP in Taiwan. STUDY DESIGN AND METHODS: This study identified 4855 incident ITP cases from the population-based National Health Insurance Research Database from mid-2006 to mid-2013, and compared incidences, patient characteristics, and clinical manifestations of ITP by age. RESULTS: Respective ITP incidence rates among those aged <15, 15 to 59, and ≥60 years were 4.0, 2.0, and 5.4 per 100,000 person-years. A male predominance was noted in children, and a female predominance was found in adults. The most common causes of secondary ITP were systemic lupus erythematosus (21.8%), viral hepatitis C (16.9%), and viral hepatitis B (13.4%). The rate of secondary ITP in children was less than one fifth that in adults (4.2% vs. 23.8%). Rates of central nervous system (1.1%) and gastrointestinal tract bleeding (3.3%) were rare, with variations by age. The rate of splenectomies in children (0.4%) was only one tenth that in adults (4.1%). The disease in 25% of children and 30% of adults became persistent or chronic. A decreasing trend in the ITP incidence was found (annual percentage change, −4.9%), and it was confined to those aged >15 years. CONCLUSION: Incidence estimates of ITP in Taiwan were close to those of Western countries, with age-specific variations in sex ratio, comorbidity, splenectomy, secondary causes, and incidence trends. The results suggest no racial variations in ITP incidences, but a geographical difference in causes of secondary ITP.