Use of a claims database to characterize and estimate the incidence rate for Castleman disease

Castleman disease (CD) is a rare lymphoproliferative disorder affecting single (unicentric; UCD) or multiple (multicentric; MCD) lymph nodes. The incidence of this difficult to diagnose disease is poorly understood, as no International Classification of Diseases, Ninth Revision (ICD-9) code is available. This study utilized a unique strategy to estimate its incidence using two commercial claims databases, IMS LifeLink (TM) and Truven Health Analytics MarketScan (R). Patients with an index diagnosis of lymphadenopathy (ICD-9 code 785.6) were followed longitudinally for 1 year prior to and 2 years post-index diagnosis date. An algorithm that identifies potential patients with CD was developed to determine the incidence rate in person-years. The incidence rate for CD was calculated as 21 (IMS LifeLink (TM)) and 25 (MarketScan (R)) per million person-years. Additionally, 23% of patients with CD were identified as potentially suffering from MCD. These results are consistent with the definition of an orphan disease, and the low incidence of the disease estimated in the literature.