Functional Criteria to Define Progressive Pulmonary Fibrosis: Searching for the Holy Grail

The authors have assessed progressive pulmonary fibrosis (PPF) criteria proposed in different studies and their association with transplant-free survival in patients with non-idiopathic pulmonary fibrosis (non-IPF). After various analyses, the authors conclude that an FVC decline of ⩾10% and six additional PPF criteria in the absence of such a reduction identify patients with non-IPF interstitial lung disease (ILD) at an increased risk of death or lung transplant. From the study's perspective, it is essential to clarify which values, methods (relative or absolute), and study periods are suitable for PPF criteria. Early identification of PPF and proper early treatment are overarching objectives. To avoid confusion in the ILD community, scientific research, and guideline groups need to work together to decide which criteria are better for the early identification of PPF.