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

Objectives: 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.

Methods: 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.

Results: 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).

Conclusion: 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.

Keywords: care patterns; diagnosis; interstitial lung disease; systemic autoimmune rheumatic diseases.

Figure 1.

Study design and time periods. Detailed schematic illustration of the study design and time periods used to assess care patterns of patients with SARD-ILD prior to their ILD diagnoses. SARD: systemic autoimmune rheumatic disease; ILD: interstitial lung disease

Figure 2.

Time to ILD diagnosis for patients with or without a pulmonologist visit in the first 90 days after early respiratory symptoms. The cumulative incidence of ILD diagnosis over a 6-year period, comparing two groups based on whether they had a pulmonologist visit within the first 90 days after early respiratory symptoms. The reference group (solid line) represents individuals without pulmonologist visit within the first 90 days, while the comparison group (dotted line) represents patients with pulmonologist visit within the first 90 days. Patients who had a pulmonologist visit within 90 days were 18% more likely to be diagnosed with ILD than those without a pulmonologist encounter (hazard ratio 1.18; 95% CI: 1.03, 1.35; P = 0.017)