Predictors of progressive pulmonary fibrosis and survival in fibrosing interstitial lung disease-related usual interstitial pneumonia

Background: Usual interstitial pneumonia (UIP) is associated with progressive pulmonary fibrosis (PPF) and poor survival in patients with fibrosing interstitial lung disease (FILD). Objectives: We aimed to investigate the predictors of PPF and survival in patients with FILD-UIP. Design: This retrospective study was conducted at a single, tertiary hospital in China. Patients underwent routine follow-up visits every 3 to 6 months according to standard operating procedures (SOPs). Methods: Patients with FILD-UIP were further stratified using the proposed PPF criteria. Results: This retrospective study enrolled 135 patients with FILD-UIP between October 2020 and December 2023, with 117 patients completing follow-up for more than 12 months. FILD-UIP was categorized as idiopathic pulmonary fibrosis (IPF) ( n =67) and non-IPF-UIP ( n =50) that included connective tissue disease-associated UIP ( n =29), hypersensitivity pneumonitis-associated UIP ( n =7), and interstitial pneumonia with autoimmune features-associated UIP ( n =14). During the follow-up period, 32 (47.8%) patients with IPF and 19 (38.0%) non-IPF-UIP experienced PPF. Pulmonary hypertension (PH) and forced vital capacity (FVC%pred) were dependent risk factors for PPF in patients with FILD-UIP, non-IPF-UIP, and IPF. King’s Brief Interstitial Lung Disease (KBILD) is a dependent risk factor for PPF in patients with FILD-UIP and IPF. PPF is similarly associated with poor survival in patients with FILD-UIP, non-IPF-UIP, and IPF. Conclusions: Baseline disease severity is closely associated with the incidence of PPF, with all forms of FILD-UIP at risk of PPF and showing similar outcomes to IPF-UIP/PPF.