Longitudinal cost of care in individuals with different subtypes of interstitial lung diseases

Background: Recently, several studies emphasized the high economic burden of interstitial lung diseases (ILDs). Most research focussed on idiopathic pulmonary fibrosis (IPF) in a cross-sectional perspective and did not disentangle disease-related and non-disease-related costs. We therefore aimed by analysing claims data to a) display the share of ILD-related costs in all-cause costs in the longitudinal view, to b) disentangle the structure of ILD-related costs and corresponding shifts over time, to c) contrast subtype specific cost profiles. Methods: We assessed quarterwise health care spending for individuals with six ILD subtypes from the year prior to diagnosis up to five years post. ILD-related expenditures were identified by ATC-Codes (medication) respectively OPS-Codes and ICD-10 diagnoses (in- and outpatient care). Mean expenditures per quarter were examined via Generalized Estimation Equations adjusted by age, gender, ILD-subtype and proximity to death. Results: Costs peaked in the quarter of diagnosis (~€4,700) with a 1/3 share of ILD-related costs. Then, costs stabilized at ~€2,000 with a quite stable 20% share of ILD-related costs. Hospital care was the main contributor to ILD-related costs (>90% in quarter of diagnosis, >50% in post diagnosis period) followed by drug-expenditures (~1/3 in post diagnosis period). Longitudinal profiles were similar across ILD-subtypes with substantial differences in level. As only exception Connective Drug associated ILDs presented an increasing share of ILD-related costs over time. Conclusion: Subtype level cost profiles mirror the mainly hospital-based diagnostic process for 1st diagnosis. Declining relevance of hospital care reflects a primarily outpatient-management during follow up.