Predictive factors of progression in mild fibrosing interstitial lung disease patients with gender-age-physiology score of 3 or less

Background: The prognostic factors in mild fibrosing interstitial lung disease (FILD) have not been established.

Methods: We retrospectively attempted to identify predictive factors of annual progression in mild FILD with gender-age-physiology (GAP) score of 3 or less using logistic regression analysis. Annual FILD progression was defined as meeting any two or more of the following conditions: 1, more than 10% decrease in forced vital capacity (FVC) or 15% decrease in diffusing capacity of the lungs for carbon monoxide (D_LCO); 2, worsening of dyspnea; 3, worsening of fibrotic change on CT at 1 year after admission.

Results: Univariate analysis showed that diagnosis of connective tissue disease-associated ILD, CT-definite usual interstitial pneumonia (UIP) pattern, composite physiologic index, FVC, D_LCO, lowest SpO₂ and decrease in SpO₂, and walk distance in the 6-minutes walk test (6MWT), chronic pulmonary emphysema assessment test (CAT) score, and some variables in Short-Form 36 were significantly associated with incidence of annual progression. Multivariate analysis showed that independent predictive factors were diagnosis of idiopathic pulmonary fibrosis (IPF) and fibrotic hypersensitivity pneumonitis (HP), CT-definite UIP pattern, lowest SpO₂ and decrease in SpO₂ in the 6MWT, and CAT score. In logistic regression analysis among 63 patients with non-IPF-ILD, diagnosis with fibrotic HP, lowest SpO₂ and decrease in SpO₂ in the 6MWT, and CAT score were also independent risk factors for annual FILD progression.

Conclusions: Exercise-induced hypoxia, patient-reported outcome, radiological UIP pattern, and diagnosis with fibrotic HP are independent predictors of annual progression in mild FILD.