Real-world care patterns and specialist encounters of patients with systemic autoimmune rheumatic disease-related interstitial lung disease in the United States: a retrospective administrative claims database analysis.

Abstract

We aimed to describe the demographics, clinical characteristics and care patterns of patients with systemic autoimmune rheumatic diseases (SARD) prior to their interstitial lung disease (ILD) diagnosis. We conducted a retrospective cohort study using claims data from Healthcare Integrated Research Database (2006-2023). Adults diagnosed with SARD-ILD were identified, with the earliest ILD diagnosis date designated as the index date. A minimum of 36 months of continuous enrolment before the index date was required. All measures were analysed descriptively. For a subset of patients with respiratory symptoms before ILD diagnosis, the association between type of specialist encounter and time from symptom onset to SARD-ILD diagnosis was assessed using a Cox proportional hazards model. The study included 2526 patients with SARD-ILD. Mean age was 62.6 years and 75.4% were female. Before ILD diagnosis, 61.8% of patients had at least one all-cause hospitalization. Diagnostic tests including chest CT, high-resolution CT, and pulmonary function tests (PFT) were used in 80.1%, 59.0% and 60.3% of patients, respectively. Among the subgroup, patients who saw a pulmonologist within 90 days of initial respiratory symptom onset were 18% more likely to be diagnosed with ILD compared with those who did not (hazard ratio: 1.18, 95% CI: 1.03, 1.35; P = 0.017). The study highlights the complex diagnostic journey of patients with SARD-ILD. Findings suggest a multidisciplinary approach involving pulmonologists and rheumatologists could enable timely ILD diagnosis and should be considered for more effective diagnosis and management of SARD-ILD.