Table 4.

Definition of Progressive Pulmonary Fibrosis

Definition of PPF
In a patient with ILD of known or unknown etiology other than IPF who has radiological evidence of pulmonary fibrosis, 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):  a. Absolute decline in FVC ⩾5% predicted within 1 yr of follow-up  b. Absolute decline in DlCO (corrected for Hb) ⩾10% predicted within 1 yr of follow-up
3	Radiological evidence of disease progression (one or more of the following):  a. Increased extent or severity of traction bronchiectasis and bronchiolectasis  b. New ground-glass opacity with traction bronchiectasis  c. New fine reticulation  d. Increased extent or increased coarseness of reticular abnormality  e. New or increased honeycombing  f. Increased lobar volume loss

Definition of abbreviations: ILD = interstitial lung disease; IPF = idiopathic pulmonary fibrosis; PPF = progressive pulmonary fibrosis.

^*Although it is critical to exclude alternative explanations of worsening features for all patients with suspected progression, this is particularly important in patients with worsening respiratory symptoms and/or decline in Dl_CO given the lower specificity of these features for PPF compared with FVC and chest computed tomography.