Progressive fibrosing interstitial lung disease (PF-ILD) is characterized by progressive
physiologic, symptomatic, and/or radiographic worsening. The real-world prevalence and
characteristics of PF-ILD remain uncertain.
Patients were enrolled from the Canadian Registry for Pulmonary Fibrosis between 2015-2020.
PF-ILD was defined as a relative forced vital capacity (FVC) decline ≥10%, death, lung
transplantation, or any 2 of: relative FVC decline ≥5 and <10%, worsening respiratory
symptoms, or worsening fibrosis on computed tomography of the chest, all within 24 months of
diagnosis. Time-to-event analysis compared progression between key diagnostic subgroups.
Characteristics associated with progression were determined by multivariable regression.
Of 2,746 patients with fibrotic ILD (mean age 65±12 years, 51% female), 1,376 (50%) met PFILD criteria in the first 24 months of follow-up. PF-ILD occurred in 427 (59%) patients with
idiopathic pulmonary fibrosis (IPF), 125 (58%) with fibrotic hypersensitivity pneumonitis (HP),
281 (51%) with unclassifiable ILD (U-ILD), and 402 (45%) with connective tissue diseaseassociated ILD (CTD-ILD). Compared to IPF, time to progression was similar in patients with
HP (hazard ratio [HR] 0.96, 95% confidence interval, CI 0.79-1.17), but was delayed in patients
with U-ILD (HR 0.82, 95% CI 0.71-0.96) and CTD-ILD (HR 0.65, 95% CI 0.56-0.74).
Background treatment varied across diagnostic subtypes with 66% of IPF patients receiving
antifibrotic therapy, while immunomodulatory therapy was utilized in 49%, 61%, and 37% of
patients with CHP, CTD-ILD, and U-ILD respectively. Increasing age, male sex,
gastroesophageal reflux disease, and lower baseline pulmonary function were independently
associated with progression.
Progression is common in patients with fibrotic ILD, and is similarly prevalent in HP and IPF.
Routinely collected variables help identify patients at risk for progression and may guide
- progressive fibrosing interstitial lung disease