Characterising Patient Pathways Prior to the Diagnosis of Interstitial Lung Disease

Background and Objective: Interstitial lung diseases (ILDs) lead to breathlessness, cough, deteriorating quality of life and early death. Patients are typically diagnosed late in their disease course when existing lung damage cannot be reversed. Accordingly, early diagnosis is the best strategy for preserving lung function and extending lifespan. Our aim was to identify signs, symptoms and health patterns and determine when they arise in the years preceding ILD diagnosis. Methods: We identified incident ILD cases from a large primary care electronic medical record database from the United Kingdom. Prevalence and timing of symptoms, signs and health patterns were compared to matched controls in the 10 years preceding diagnosis. Results: ILD patients (N = 18,914) had symptoms of dyspnoea, cough, fatigue, weight loss and loss of appetite recorded more frequently compared to controls (N = 60,156). Most patients (73%) reported cough or dyspnoea at least once at a primary care visit, with 13%–17% recording symptoms on ≥ 5 separate occasions (dyspnoea: 13% cases, 5% controls; cough: 17% cases, 7% controls). ILD patients had a greater cumulative incidence of cough and dyspnoea even 10 years before diagnosis (OR: 1.73 [1.58, 1.89], p < 0.001), with the odds ratio increasing to 2.38 at 1 year before diagnosis. Most ILD patients were initially diagnosed with another respiratory condition (95%–97%) or heart failure (4%–9%). Conclusion: Gradual onset of non-specific symptoms over 10 years, coupled with referrals to other specialities and misdiagnoses, delays ILD diagnosis. Improving awareness of ILD among primary care practitioners may shorten the time to diagnosis and expedite access to treatments.