Background: Idiopathic pulmonary fibrosis (IPF) and connective tissue disease-associated interstitial lung diseases (CTD-ILDs) were the most common causes of fibrotic interstitial lung diseases (ILDs). An assessment of the prognosis of IPF based on a GAP score has been developed using factors such as sex, age, FVC, and diffusing capacity of the lung for carbon monoxide (DLCO). However, the GAP score does not account for dyspnea severity or functional impairment during walking. Furthermore, previous studies have only examined the use of GAP score in patients with IPF.

Methods: Between December 2018 and August 2021, we recruited patients with newly diagnosed ILD through expert multidisciplinary discussion (MDD). An examination of GAP score, 6-minute walking distance (6MWD), FVC and DLCO was performed. A one-year mortality notification was provided prospectively to patients. 

Results: We enrolled 104 patients diagnosed with fibrotic ILD, and 12 (11.5%) died after a one-year follow-up. Using a Cox regression model, GAP score, mMRC, DLCO and 6MWD were associated with survival. DLCO, mMRC, and 6MWD were combined as functional scores for mortality prediction. Multivariable analysis found that only GAP score (HR: 1.55, 1.03?2.34, p = 0.032) and functional score (HR: 3.45, 1.11?10.73, p = 0.032) were significantly associated with survival. Functional score ? 2 points was associated with 1-year mortality after adjustment for confounding factors.

Conclusion: In both IPF and CTD-ILD, the functional score including the mMRC, DLCO and 6MWD predicts mortality better than the GAP score.