Primary immune thrombocytopenia in US clinical practice: incidence and healthcare burden in first 12 months following diagnosis.

Primary immune thrombocytopenia (ITP), an autoimmune disorder characterized by low platelet count, can lead to serious bleeding events. Little is known about the current epidemiology of ITP in the US, and even less is known about the current healthcare burden of ITP, especially in the 12-month period following ITP diagnosis. We used a retrospective cohort design and data from two US private healthcare claims databases (2010-2016) to identify persons with evidence of newly diagnosed ITP. We weighted estimates of the annual incidence of ITP by age and sex to reflect the US population, and summarized healthcare utilization and expenditures (2016 US$) during the first 12 months after ITP diagnosis ("follow-up period"). Annual incidence of ITP in the US was 6.1 per 100,000 persons, higher among females versus males (6.7 vs. 5.5), and highest among children aged 0-4 years (8.1) and adults aged ≥65 years (13.7). Patients with ITP averaged 0.33 (95% CI: 0.32-0.35) hospitalizations and 15.3 (15.1-15.6) ambulatory encounters during the follow-up period; mean total healthcare expenditures during this period were $21,290 (20,502-22,031). Hospitalizations were more common during the first 3 months following diagnosis, and were twice as frequent among children versus adults; expenditures for ambulatory encounters were substantially higher for adults versus children aged 0-4 years. Our findings suggest that nearly 20,000 children and adults are newly diagnosed with ITP each year in the US, substantially higher than previously reported. Among patients requiring formal medical care, the economic burden during the first 12 months following diagnosis is high, with estimated US expenditures totaling over $400 million.