Definition of Progressive Pulmonary Fibrosis According to ERS
Progressive pulmonary fibrosis (PPF) is defined by the 2022 ATS/ERS/JRS/ALAT guideline as the presence of at least two of three specific criteria occurring within the past year in patients with interstitial lung disease (other than IPF) who have radiological evidence of pulmonary fibrosis, with no alternative explanation for the worsening. 1
The Three Diagnostic Criteria
PPF requires at least 2 of the following 3 criteria to be present within the past 12 months: 1
1. Worsening Respiratory Symptoms
- Progressive dyspnea or other respiratory symptoms with no alternative explanation 1
2. Physiological Evidence of Disease Progression (Either of the following):
- Absolute decline in FVC >5% predicted within 1 year of follow-up 1
- Absolute decline in DLCO (corrected for hemoglobin) >10% predicted within 1 year of follow-up 1
3. Radiological Evidence of Disease Progression (One or more of the following):
- Increased extent or severity of traction bronchiectasis and bronchiolectasis 1
- New ground-glass opacity with traction bronchiectasis 1
- New fine reticulation 1
- Increased extent or increased coarseness of reticular abnormality 1
- New or increased honeycombing 1
- Increased lobar volume loss 1
Critical Exclusion Requirement
Alternative explanations for worsening must be excluded in all patients with suspected PPF. 1 This is particularly important for patients with worsening respiratory symptoms and/or decline in DLCO, given the lower specificity of these features for PPF compared with FVC decline and chest CT findings. 1
Population to Which This Definition Applies
This definition applies specifically to patients with ILD of known or unknown etiology OTHER than IPF who have radiological evidence of pulmonary fibrosis. 1 IPF itself is excluded from the PPF definition because virtually all IPF patients manifest disease progression, making the term redundant for this population. 1
Clinical Context
The radiological progression criteria on HRCT were validated as a stand-alone predictor of reduced transplant-free survival, emphasizing the prognostic importance of imaging findings in PPF. 1 The pattern of radiological progression in non-IPF ILDs is variable and may include evolution of ground-glass abnormality to reticular abnormality, evolution of reticular abnormality to honeycombing, and/or increase in traction bronchiectasis/bronchiolectasis. 1