Epidemiology of immune thrombocytopenic purpura in the General Practice Research Database

The epidemiology of immune thrombocytopenic purpura (ITP) is not well-characterised in the general population. This study described the incidence and survival of ITP using the UK population-based General Practice Research Database (GPRD). ITP patients first diagnosed in 1990-2005 were identified in the GPRD. Overall incidence rates (per 100 000 person-years) and rates by age, sex, and calendar periods were calculated. Survival analysis was conducted using the Kaplan-Meier and proportional hazard methods. A total of 1145 incident ITP patients were identified. The crude incidence was 3.9 (95% confidence interval [CI]: 3.7-4.1). Overall average incidence was statistically significantly higher in women (4.4, 95% CI: 4.1-4.7) compared to men (3.4; 95% CI: 3.1-3.7). Among men, incidence was bimodal with peaks among ages under 18 and between 75-84 years. The hazard ratio for death among ITP patients was 1.6 (95% CI: 1.3-1.9) compared to age- and sex-matched comparisons. During follow-up 139 cases died, of whom 75 had a computerised plausible cause of death. Death was related to bleeding in 13% and infection in 19% of these 75. In conclusion, ITP incidence varies with age and is higher in women than men. This potentially serious medical condition is associated with increased mortality in the UK.