Assessment of progressive pulmonary fibrosis and idiopathic pulmonary fibrosis in German claims data: algorithm development to reflect real-world disease progression

Background : Identifying patients with Idiopathic Pulmonary Fibrosis (IPF) and Progressive Pulmonary Fibrosis (PPF) in health insurance claims data is challenging due to the lack of clinical measures of disease progression in such databases. However, accurate identification is essential to meet the growing demand for research-driven healthcare planning and targeted support for affected patients. The aim was to develop algorithms for identifying IPF and PPF populations within German claims data, with a focus on assessing appropriate proxies for disease progression. Methods : We designed algorithmic definitions for IPF and PPF based on diagnostic codes, procedure codes and prescription data. Particular attention was given to proxies indicating disease progression, such as usage of high-resolution CT usage, lung biopsy, bronchoalveolar lavage, or prescription of oxygen, antifibrotic and immunosuppressive drugs. Multiple algorithms were developed by adjusting the stringency of progression-related parameters, especially temporal patterns of events. These variants were compared to assess their impact on estimated population sizes and to evaluate plausibility against known epidemiological benchmarks for prevalence and incidence. Results : Preliminary findings show that modifications in algorithmic definitions of progression substantially affect the identified patient populations. More inclusive definitions yield broader but potentially less specific cohorts, while stricter criteria may miss relevant cases. Balancing sensitivity and specificity is critical to realistically approximate the real-world IPF and PPF populations. The feasibility of the various algorithms is assessed based on the epidemiological data available in the literature. Conclusion : Our algorithmic framework enables nuanced identification of IPF and PPF patients in German claims data. This approach highlights the importance of transparency in defining progression-related criteria to ensure alignment with clinical reality and research objectives. Publication History Article published online: 04 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany