Chart 2. Criteria for evaluating progressive fibrosing interstitial lung diseases.^a .

PPF is defined as at least two of the following three criteria occurring within the past year with no alternative explanation:
1. Worsening respiratory symptoms
2. Physiological evidence of disease progression (either of the following): • Decline in FVC ≥ 5% predicted within 1 year of follow-up • Decline in DLCO (corrected for hemoglobin) ≥ 10% predicted within 1 year of follow-up
3. Radiological evidence of disease progression (one or more of the following): • Increased extent or severity of traction bronchiectasis and bronchiolectasis • New ground-glass opacity with traction bronchiectasis • New fine reticulation • Increased extent or increased coarseness of reticular abnormality • New or increased honeycombing • Increased lobar volume loss

PPF: progressive pulmonary fibrosis. ^aBased on Raghu et al.⁽⁴⁾