PRO39 PREVALENCE OF PRIMARY IMMUNE THROMBOCYTOPENIA AMONG TEXAS MEDICAID BENEFICIARIES: ANALYSES OF AN ADMINISTRATIVE CLAIMS DATABASE

Abstract

Prevalence estimates of primary immune thrombocytopenia (ITP) in the U.S. need to be updated. This study aimed to investigate the prevalence of primary ITP among Texas Medicaid beneficiaries. A retrospective analysis was conducted using Texas Medicaid claims for calendar years 2012-2015. ITP patients were identified using ICD-CM-9 code 287.31 and ICD-CM-10 code D69.3, with a requirement of two claims for ITP separated by at least 30 days. We excluded patients with concurrent diagnoses that made ITP unlikely or secondary to other diseases. The annual prevalence was calculated based on the average number of people enrolled monthly in Texas Medicaid. Three categories, “newly diagnosed”, “persistent” and “chronic” ITP were identified when the time durations between the first and the last claims for ITP were less than 3 months, 3 to 12 months, and more than 12 months, respectively. All analyses were performed using SAS 9.4. A total of 3,968 patients in the database had claims for ITP, from which 633 (16.0%) had diagnoses of exclusion, including malignant neoplasms, systemic lupus erythematosus (SLE), human immunodeficiency virus (HIV) and other diseases. Subsequently, 1,682 were excluded when requiring two claims for ITP separated by at least 30 days, leaving 1,653 identified as primary ITP patients, in which 330 (20.0%) were newly diagnosed, 564 (34.1%) were persistent and 759 (45.9%) were chronic ITP patients. About two-thirds (62.3%) of ITP patients were female and about half (50.8%) were under 18. The average annual prevalence of primary ITP was 21.5 (95% CI: 20.1 to 23.1) per 100,000 persons. The annual prevalence of primary ITP among Texas Medicaid beneficiaries was consistent with previous national estimates. Nearly half of the ITP patients in this population were identified as chronic. Care must be taken to exclude non-ITP or secondary ITP patients in prevalence estimates based on claims data.