Proposed criteria that may be used in clinical practice to assess disease progression in fibrotic interstitial lung diseases

Lung function
  • Rate of decline in FVC (mL·year−1)

  • Absolute or relative changes in FVC (mL or % predicted)

  • Absolute or relative changes in DLCO % predicted

Exercise capacity
  • Absolute change in 6-min walk test distance

  • Change in oxygen saturation nadir during 6-min walk test

Change in maximal exercise capacity
Symptoms and patient-reported outcomes
  • Change in symptoms

  • Change in everyday life exercise capacity

  • Questionnaires on shortness of breath, cough, and/or quality of life

Acute worsening
  • Acute exacerbation of fibrosis (idiopathic or triggered)

  • Non-elective hospitalisation for a respiratory cause

  • Change in the extent or texture of fibrotic features on HRCT

  • Change in quantitative fibrosis scores on HRCT#

Need for supportive care
  • Initiation of ambulatory oxygen therapy at exercise

  • Initiation of supplemental oxygen therapy at rest, or change in flow of oxygen

Serum biomarkers
  • None validated

  • Not yet applicable in clinical practice

As these criteria are intended to guide individual decisions in clinical practice, they may differ from end-points used in clinical trials [17]. Most clinicians would make management decisions based on a combination of variables. HRCT: high-resolution computed tomography; FVC: forced vital capacity; DLCO: diffusing capacity of the lung for carbon monoxide. #: not yet routinely available.