2. Department of Epidemiology, Merck Research Laboratories, 351 N. Sumneytown Pike, North Wales, PA 19454, USA.
Background: We developed and validated an algorithm to evaluate pure red cell aplasia (PRCA) incidence in chronic hepatitis C (CHC) patients in a large observational database.
Methods: We conducted a retrospective study using the HealthCore Integrated Research DatabaseSM (HIRD) in which we identified CHC patients and followed them forward to identify PRCA occurrences. Possible PRCA cases were identified based on a medical claim for aplastic anemia (ICD-9-CM 284.8x or 284.9x) with a claim for bone marrow biopsy in the prior 30 days. Medical records were requested and reviewed by an Adjudication Committee (AC) to confirm PRCA case status. The positive predictive value (PPV) and 95% confidence interval (CI) for the PRCA algorithm were estimated based on adjudication results.
Results: A total of 36,164 CHC patients were identified yielding 25 suspected PRCA cases. Medical records were obtained and reviewed for 17 cases. Of these 17 cases, none were confirmed as PRCA (PPV: 0.0%; 95% CI 0.0-19.5%). Estimated confirmed PRCA incidence was 0.0/1,000 person-years (95% CI 0.00-0.05/1,000 person-years).
Conclusions: Automated case definitions for PRCA performed poorly in identifying PRCA in CHC patients, limiting our ability to estimate PRCA incidence. PRCA in CHC patients is rare and difficult to study using large automated databases.
Keywords: Observational study, hepatitis C, chronic, red-cell aplasia, pure, incidence