Risk of cataract among idiopathic thrombocytopenic purpura patients in the UK general practice research database.

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.