Renal impairment, hemoglobinuria, and hemoglobinemia among patients with idiopathic thrombocytopenic purpura.

Renal impairment (RI) and events potentially leading to RI were reported in idiopathic thrombocytopenic purpura (ITP) patients with specific medications. This study was conducted to estimate the incidence rate (IR) of RI, hemoglobinuria and hemoglobinemia (HE) and characterize baseline risk factors in ITP and ITP-free patients. Incident ITP and matched non-ITP patients were identified from an electronic medical record database from 1990 to 2002. ITP patients were classified by the treatment first received (initiators) or ever received (users). All cohorts were followed for study outcomes. IRs were calculated and standardized by age and gender. A total of 881 ITP and 4,496 ITP-free patients yielded 3,044 and 16,006 person-years, respectively. The ITP cohort had a slightly higher prevalence of autoimmune diseases and infections than the ITP-free cohort. The IR (/10,000 person-years) for RI, hemoglobinuria and HE was 14.2, 35.7, and 7.1 in the ITP cohort; 10.0, 48.8, and 0 in the ITP-free cohort; and 18.3, 37.1, and 6.1 in untreated ITP patients, respectively. The risk of RI, HE or hemoglobinuria was not found to differ substantially between ITP and non-ITP patients or across ITP treatments.