Ivy Altomare, Karynsa Cetin, Sally Wetten, Jeffrey S Wasser

Immune thrombocytopenia (ITP) is a rare disorder characterized by low platelet counts and an increased tendency to bleed. The goal of ITP therapy is to treat or prevent bleeding. Actual rates of bleeding are unknown. Clinical trial data may not reflect real-world bleeding rates because of the inclusion of highly refractory patients and more frequent use of rescue therapy. We used administrative medical claims data in the US to examine the occurrence of bleeding-related episodes (BREs) - a composite end point including bleeding and/or rescue therapy use - in adults diagnosed with primary ITP (2008-2012). BRE rates were calculated overall and by ITP phase and splenectomy status. Patients were followed from ITP diagnosis until death, disenrollment from the health plan, or June 30, 2013, whichever came first. We identified 6,651 adults diagnosed with primary ITP over the study period (median age: 53 years; 59% female). During 13,064 patient-years of follow-up, 3,768 patients (57%) experienced ≥1 BRE (1.08 BREs per patient-year; 95% confidence interval: 1.06-1.10). The majority (58%) of BREs consisted of rescue therapy use only. Common bleeding types were gastrointestinal hemorrhage, hematuria, ecchymosis, and epistaxis. Intracranial hemorrhage was reported in 74 patients (1%). Just over 7% of patients underwent splenectomy. Newly diagnosed and splenectomized patients had elevated BRE rates. We provide current real-world estimates of BRE rates in adults with primary ITP. The majority of ITP patients experienced ≥1 BRE, and over half were defined by rescue therapy use alone. This demonstrates the importance of examining both bleeding and rescue therapy use to fully assess disease burden.