Purpose: To estimate the incidence of cataracts in an adult idiopathic thrombocytopenic purpura (ITP) and in a comparable non-ITP population, stratified by age, gender and medication use in order to determine whether the risk of cataracts is greater in ITP patients.
Methods: Retrospective cohort of 745 newly diagnosed ITP patients and 3725 non-ITP subjects who were 18 years of age or older. The study population included patients registered on the General Practice Research Database (GPRD) during the period 1992-2005. ITP patients, identified using Read/Oxmis codes, were matched to five non-ITP patients. The exposure of interest was oral systemic steroid use and the primary outcome was cataracts.
Results: The overall incidence rate of cataracts in males was 11.8 per 1000 PY (95%CI: 6.3-20.2) and in females 9.0 per 1000 PY (95%CI: 5.2-14.4). In the non-ITP population these rates were 14.0 per 1000 PY (95%CI: 11.0-17.4) and 8.1 per 1000 PY (95%CI: 6.4-10.1), respectively. In the ITP population, users of oral steroids (OS) had a cataract incidence rate of 14.0 per 1000 PY (95%CI: 8.7-21.4) and non-users 6.0 per 1000 PY (95%CI: 2.8-11.4). In the non-ITP population, these rates were 16.9 per 1000 PY (95%CI: 11.9-23.3) and 9.2 per 1000 PY (95%CI: 7.6-11.0), respectively. OS were associated with an increased risk for cataracts.
Conclusions: The rates of cataract in an adult ITP population are comparable to that in a non-ITP population.