# Progression in Fibrotic Interstitial Lung Diseases: Prevalence and Indicators in the Initial Evaluation in a Brazilian Multicentric Cohort

## TL;DR

This study found that fibrotic hypersensitivity pneumonitis is the most progressive lung disease in Brazil, with specific indicators like dyspnea and low oxygen levels predicting disease progression.

## Contribution

The study identifies FHP as the most progressive fibrotic ILD in Brazil and highlights specific clinical indicators for predicting progression.

## Key findings

- 40.5% of patients showed disease progression after two years.
- Fibrotic hypersensitivity pneumonitis had the highest progression rate at 52%.
- Dyspnea, crackles, and low oxygen levels were significant indicators of progression.

## Abstract

Objective: This retrospective study aimed to determine the prevalence of progression in fibrotic interstitial lung disease (ILD) and the findings at diagnosis most associated with progression after two years of follow-up in a large Brazilian cohort.

Methods: This was a retrospective multicenter observational study in Brazil. Progression was defined after two years of follow-up. We excluded patients with an initial peripheral oxygen saturation (SpO2) of less than 88% or an initial forced vital capacity (FVC) of less than 45%. Diagnoses were made by multidisciplinary discussion. Patients with idiopathic pulmonary fibrosis were included for comparison. At least one of the following events was indicative of progressive ILD: (1) a relative decrease in FVC of 10% or more, (2) worsening dyspnea, (3) a greater extent of fibrotic findings on high-resolution computed tomography (HRCT), (4) initiation of oxygen, and (5) death attributed to ILD. Logistic regression analysis was used to identify risk factors for progressive fibrosis.

Results: The mean age of patients was 61.7±12.3 years, and 69.5% had Velcro crackles. The mean FVC was 71.6±15.8%, and 26.1% showed honeycombing on HRCT. After two years of follow-up, 40.5% of patients (n=154) showed disease progression. Fibrotic hypersensitivity pneumonitis (FHP) was the most progressive disease (52%), and connective tissue disease-associated ILD (CTD-ILD) was the least progressive (25%). Multivariate analysis showed that a higher score for dyspnea, crackles, and SpO2 at rest ≤94% and ≤85% at the end of exercise were significant indicators of progression. Diffusing lung capacity for carbon monoxide (DLCO) was measured in 172 cases, with values <55% predicting a high odds ratio for progression (OR=4.03; 2.10-7.69).

Conclusion: In Brazil, FHP is the most progressive disease and CTD-ILD is the least progressive after two years of follow-up. The degree of dyspnea, crackles, SpO2 at rest and during exercise, and DLCO at baseline are associated with progressive disease.