Refusal to participate in the study

Patients unable to provide informed consent for participation in the study

IPF exacerbation in the 6 months prior to enrollment

Previous diagnosis of chronic airway disease (e.g., bronchial asthma, chronic obstructive bronchitis, bronchiectasis with a cause other than IPF)

Presence of bronchial obstruction defined by an FEV1/FVC (or FEV1/VC) ratio below the lower limit of normal

Chronic therapy with long-acting bronchodilators or combinations of bronchodilators and inhaled corticosteroids

Inability of the patient to perform reproducible pulmonary function tests

Chronic treatment with systemic corticosteroids or immunosuppressants

Concomitant lung or pleural cancer

Pregnancy or breastfeeding women

Small Airways Disease Functional Assessment in Idiopathic Pulmonary Fibrosis (SWIFT-IPF)