Epidemiology of Immune Thrombocytopenic Purpura in the United Kingdom, Germany, and the Netherlands.

Background: Immune thrombocytopenic purpura (ITP) is an autoimmune disorder that is associated with serious clinical and health-related quality of life consequences. However, the true burden of ITP is not known because there is limited published data on its incidence and prevalence.

Aims: To describe the incidence and prevalence of ITP over time among adults in selected European countries (United Kingdom, Germany, and the Netherlands) and to ascertain whether ITP incidence and prevalence differ by age or sex.

Methods: ITP incidence and prevalence rates were calculated from three healthcare databases: the General Practitioners Research Database (UK), the IMS Disease Analyzer (UK and Germany), and the PHARMO Database (the Netherlands). These databases contain longitudinal patient medical record information from selected general practitioners and specialists, using samples designed to be representative of the countries of interest. Patient information is acquired through electronic linkages to providers’ practices in the GPRD and IMS Disease Analyzer, and through the Dutch National Medical Registry in PHARMO. The study periods were 1990–2000 (GPRD), 1994–2003 (IMS Disease Analyzer), and 1991–2003 (PHARMO); analyses were restricted to persons 19 years and older. ITP diagnoses were identified using the ICD-9-CM 287.3 and ICD-I0-CM D69.3 codes. Incidence rates as calculated include only first-time diagnoses whereas prevalence rates include all new and existing cases during a given year.

Results: As shown in the table, average ITP incidence and prevalence rates during the study periods (10 years or more) were generally similar in the UK, Germany, and the Netherlands; for example, average incidence rates ranged from 0.6–3.0 per 100,000 persons/year. Although the differences were relatively minor, in general, incidence and prevalence appeared to be highest in Germany and lowest in the Netherlands. From all databases and years of study, persons 60 years and older had the highest age/sex-specific incidence and prevalence. Incidence and prevalence rates were also generally higher (7–36%) among women than men.

Summary/Conclusions: During all study years, the incidence and prevalence of ITP in the UK, Germany, and the Netherlands was less than 10 per 100,000 persons/year and was relatively stable over time. ITP was more frequent among women and persons over 60 years of age. While studies derived from databases of medical records have potential limitations, such as disease misclassification, selection bias, or omissions/recording errors, our findings are consistent with other published investigations showing that ITP incidence and prevalence is fairly low in European countries.