Background
Autoimmune rheumatologic disease associated interstitial lung diseases (ARD-ILD) are rare conditions and the association between ARDs and respiratory symptoms often goes unrecognised by ARD patients and general practitioners (GPs). The diagnostic trajectory from the first respiratory symptoms to an ARD-ILD diagnosis is often delayed and may increase the burden of symptoms and allow further disease progression.The aim of this study was to 1) characterise the diagnostic trajectories of ARD-ILD patients and to 2) identify barriers for obtaining a timely ILD diagnosis based on the experiences and perceptions of both patients and healthcare professionals.

Method
Semi-structured qualitative interviews were conducted with Danish ARD-ILD patients, rheumatologists, pulmonologists and ILD nurses.

Results
Sixteen patients, six rheumatologists, three ILD nurses and three pulmonologists participated. Five characteristics of diagnostic trajectories were identified in the patient interviews: 1) early referral to lung specialists; 2) early delay; 3) delay or shortcut depending on specific circumstances; 4) parallel diagnostic trajectories connected late in the process; 5) early identification of lung involvement without proper interpretation. With the exception of early referral to lung specialists, all of the diagnostic trajectory characteristics identified led to delayed diagnosis. Delayed diagnostic trajectories resulted in patients experiencing increased uncertainty. Inconsistent disease terminology, insufficient knowledge and lack of awareness of ARD-ILD among central healthcare professionals and delayed referral to ILD specialists were main contributors to the diagnostic delay identified by the informants.

Conclusion
Five characteristics of the diagnostic trajectories were identified, four of which led to diagnostic delay of ARD-ILD. Improved diagnostic trajectories can shorten the diagnostic trajectory and increase early access to appropriate specialist medical care. Improved awareness and expertise in ARD-ILD across different medical specialties, especially among GPs, may contribute to more efficient and timely diagnostic trajectories and improved patient experiences.