# Predictors of Progressive Fibrosing Interstitial Lung Diseases and Survival in Fibrosing Interstitial Lung Disease-Related Usual Interstitial Pneumonia

## TL;DR

This study identifies risk factors for progressive fibrosing lung disease in patients with fibrosing interstitial lung disease, finding similar outcomes to idiopathic pulmonary fibrosis.

## Contribution

The study identifies baseline severity and specific clinical factors as predictors of progressive fibrosing interstitial lung disease in FILD-UIP patients.

## Key findings

- Pulmonary hypertension and FVC%pred are risk factors for PF-ILD in FILD-UIP patients.
- PF-ILD is associated with poor survival across all FILD-UIP subtypes.
- KBILD score is a significant predictor of PF-ILD in FILD-UIP and IPF.

## Abstract

Background and Objectives: Usual interstitial pneumonia (UIP) is associated with progressive fibrosing interstitial lung diseases (PF-ILD) and poor survival in patients with fibrosing interstitial lung disease (FILD). We aimed to investigate the predictors of PF-ILD and survival in patients with FILD-UIP. Materials and Methods: 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). Patients with FILD-UIP were further stratified using the proposed PF-ILD criteria. Results: This retrospective study enrolled 150 patients with FILD-UIP between October 2020 and June 2025, 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), which 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 PF-ILD. Pulmonary hypertension (PH) and predicted percentage of forced vital capacity (FVC%pred) were dependent risk factors for PF-ILD in patients with FILD-UIP, non-IPF-UIP, and IPF. King’s Brief Interstitial Lung Disease (KBILD) is a dependent risk factor for PF-ILD in patients with FILD-UIP and IPF. PF-ILD 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 PF-ILD, with all forms of FILD-UIP at risk of PF-ILD and showing similar outcomes to IPF-UIP/PF-ILD.