Abstract
Background and Objectives: Progressive pulmonary fibrosis (PPF) is a recently described term reserved for patients with fibrotic ILD other than idiopathic pulmonary fibrosis (IPF) with fast clinical deterioration. Here, survival and prognostic biomarkers at the time of diagnosis for PPF are investigated in a fibrotic ILD other than IPF cohort (non-IPF). Materials and Methods: Patients diagnosed during the period of 2012-2018 at the ILD Center of Excellence (St. Antonius Hospital, Nieuwegein, The Netherlands) with a fibrotic ILD were included in this study. The presence of PPF was investigated using the criteria from the updated IPF/PPF guideline during the first year after diagnosis. Logistic regression analysis was used to determine risk factors for PPF. A Kaplan-Meier survival analysis with log-rank test was conducted to analyze survival in patients with and without PPF. Results: This study included 304 non-IPF patients and, for comparison, 379 IPF patients. In non-IPF patients, 146 (46%) fulfilled ≥2 criteria for PPF. These patients had a median transplant-free survival rate of 2.9 ± 0.4 years, which was worse than non-IPF patients without PPF (10.1 ± 1.8 years, p < 0.001). The risk for PPF was increased in patients with FVC < 50% (odds ratio (OR) of 2.50, 95% CI = 1.01-6.17, p = 0.047) or DLCOc ≤ 35% (OR = 2.57, 95% CI = 1.24-5.35, p = 0.011). In the first 3 years after diagnosis, survival in PPF and IPF is the same, while in the following years IPF has a significantly worse survival. Conclusions: The non-IPF cohort with PPF had a significantly worse transplant-free survival compared with the non-IPF cohort without PPF. Independent risk factors for PPF in non-IPF were FVC < 50% and DLCOc ≤ 35%.