Healthcare utilization in the diagnostics of interstitial lung disease

<bold>Background:</bold> The diagnostics of interstitial lung disease (ILD) is often considerably delayed. Despite the potential of an improved outcome following early diagnosis, few studies have focussed on healthcare utilization and the diagnostic pathway. We aimed to compare healthcare utilization and the diagnostic pathway in patients with ILD and matched controls <bold>Methods:</bold> We performed a nationwide register-based matched cohort study in patients diagnosed with ILD in Denmark between 2011 and 2019. Ten persons were randomly matched for each patient. Incidence rate ratios (IRR) for general practitioner (GP) and hospitals contacts as well as diagnostic procedures were calculated up to 10 years prior to the ILD diagnosis and adjusted for socioeconomic factors and comorbidity status <bold>Results:</bold> The cohort consisted of 13,151 patients with ILD and 131,510 matched controls. IRRs were higher for patients compared to controls for GP consultations, hospital and respiratory hospital admissions, as well as C-reactive protein and spirometry measurements five years before ILD diagnosis (IRRs 1.13-1.98, 95% CIs 1.09-2.35) and increasing during the last year (IRRs 1.56-23.89, 95% CI 1.54-25.55). A higher comorbidity level increased healthcare utilization and decreased the relative difference between patients and controls <bold>Conclusion:</bold> Patients had higher healthcare utilization and underwent more diagnostic procedures, especially five years before diagnosis, increasing considerably in the last year before diagnosis; the most pronounced difference was observed in patients with few comorbidities. Patients and healthcare professionals thus respond to respiratory symptoms up to five years before the ILD diagnosis, which could enable an earlier diagnosis