(AG) A Population-Based Study on The Prevalence of Diagnosed Primary Immune Thrombocytopenia in the United States, 2016-2021

Publication Number: 1031

Background: Primary immune thrombocytopenia (ITP, formerly known as immune thrombocytopenic purpura) is a rare, autoimmune-mediated disorder of low platelets (thrombocytopenia) characterized by increased platelet destruction and impaired production in the absence of an identified underlying condition. The epidemiology of primary ITP is incompletely described and there is limited published data on the number of patients diagnosed with primary ITP in the United States.

Objectives: To estimate the prevalence of diagnosed primary ITP among pediatric and adult patients in the United States

Methods: We conducted a retrospective cohort study using an existing Optum Market Clarity Electronic Health Records (EHR) database from April 1, 2016 through March 31, 2021. Adult and pediatric patients with primary ITP were defined as those with at least two “ITP diagnoses” (ICD10: D69.3) and any of the subsequent ITP diagnoses occurring at least 30 days after the index diagnosis. Patients with less than 6 months of EHR data prior to the index ITP diagnosis or with secondary ITP diagnoses or other causes for thrombocytopenia (including other autoimmune disorders, chronic lymphocytic leukemia, Hodgkin’s disease, non-Hodgkin’s lymphoma, and systemic lupus erythematosus) were excluded. The prevalence of diagnosed primary ITP among pediatric and adult patients was estimated by weighting the prevalence in the database by the 2019 US Census and adjusting for age, sex, race, and ethnicity.

Results: A total of 20,146 patients with primary ITP were identified. The weighted estimated prevalence of diagnosed primary ITP between April 2016 and March 2021 was 0.0368% (36.8 cases per 100,000). Among pediatric ITP patients (age < 18 years), 51.6% were female, and 8.1%, 57.7%, and 34.2% were in the age groups of 0-1, 2-11, and 12-17 years of age. Among adult ITP patients, 55.5% were female, and 23.0%, 38.8% and 38.2% were in the age groups of 18-39, 40-64, and ≥64 years of age including 18.7% aged ≥75.

Conclusions: This population-based retrospective cohort study provides an updated national estimate of the prevalence of diagnosed ITP in the United States. In comparison with the previously reported prevalence of chronic (condition was present for ≥6 months) ITP patients as 23.5 cases per 100,000 from 2002 to 2006 in the US, the current estimate of 36.8 cases per 100,000 covers the full breadth of ITP and highlights the burden of disease in the pediatric population.