TABLE 1

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 D_LCO % 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
HRCT	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; D_LCO: diffusing capacity of the lung for carbon monoxide. ^#: not yet routinely available.