Abstract / Summary
Progressive fibrosing interstitial lung diseases (PF-ILDs), including idiopathic pulmonary fibrosis (IPF), are characterised by irreversible fibrosis and poor prognosis. Despite the importance of timely identification, diagnostic delays remain common. This review aimed to summarise studies reporting time to diagnosis in PF-ILDs to identify reasons for diagnostic delays and the impact on several clinical and economic outcomes. Database (Embase, MEDLINE, Cochrane Library, LILACS and grey literature) searches were conducted on 15 July 2024 and updated on 5 June 2026. Observational studies reporting time to diagnosis in PF-ILD published between 2002 and 2026 were identified. 34 studies representing 36 621 patients from 41 countries met the inclusion criteria. Dyspnoea, cough and fatigue were the most common presenting symptoms. Median time from symptom onset to diagnosis ranged between 6.0 and 25.2 months; mean estimates varied from 9.6 to 39.3 months in IPF and exceeded 30.2 months in non-IPF PF-ILD. Between 30% and 77% of patients experienced delays >12.0 months. An increased diagnostic time was associated with more advanced disease, worse survival, poorer quality of life and increased hospitalisation rate. Across included studies, between 21% and 87% of patients were misdiagnosed (often with cardiovascular or other respiratory diseases) and received treatment for other conditions. Predictors of delayed diagnosis included older age, comorbidities, misdiagnosis, previous therapy and absence of early imaging or multidisciplinary evaluation. Patients with PF-ILD, including IPF, face a long time to diagnosis, associated with unfavourable clinical and healthcare resource outcomes, with limited evidence on cost outcomes. Direct economic burden resulting from delayed diagnosis is currently poorly understood and needs further research.