A Comparison of the Sex-Specific Incidence of Immune Thrombocytopenia in Children, Teenagers, and Adults in the General Practice Research Database.

Immune thrombocytopenia (ITP) is an autoimmune condition characterized by low blood platelet counts. It has been reported that the epidemiology of ITP in the pediatric population (<18 years old) is different from that in adults. We therefore assessed the incidence of ITP in the pediatric population as compared to the adult population in a large UK-based primary care database – the General Practice Research Database (GPRD).

We identified all patients with a first-time diagnosis of ITP recorded in the GPRD during the period from 1990 to 2005. Age- and sex-specific incidences of ITP were estimated as the number of patients with a first-time recorded diagnosis of ITP divided by the person-time contributed by all subjects in the database who did not have a diagnosis of ITP.

Of the total of 1,146 incident cases of ITP among 29.2 million person-years (PY) of observation from 1990 to 2005, we observed 257 incident cases of pediatric ITP (<18 years old) in 6.1 million PY, of whom 197 were children (aged less than 10 years) and 60 were teenagers (10 – 17 years old) at diagnosis. The age-specific incidence estimate for ITP in children was 5.7 per 100,000 PY [95% confidence interval (CI): 5.0 – 6.6 per 100,000 PY], with a statistically significantly 60% higher incidence in boys compared to girls. By contrast, among teenagers the overall incidence was lower [2.2 (95% CI: 1.7 – 2.9) per 100,000 PY] with a suggestion of a 50% higher incidence rate in girls compared to boys. The overall incidence in the adult population was 3.8 (95% CI: 3.6 – 4.1) per 100,000 PY, with women having a statistically significantly 48% higher incidence compared to men.

Our results showed an interaction between age and sex with ITP incidence, suggesting that patterns of disease burden differ among children, teenagers, and the adult population. Further investigation into these differences, including comorbidities and treatment practices is warranted.

This study was supported by Amgen Inc.

Yong:Amgen Inc.: Employment, Equity Ownership. Schoonen:Amgen Inc.: Employment, Equity Ownership. Kaye:Amgen Inc.: Research Funding.