*Demographics include, but are not limited to, age, gender, ethnicity, health insurance and so on. Patients have the right to decline providing answers for questions related to personal privacy.

†Existing risk factors for IPF include smoking, environmental exposure, occupational exposure/hazards, drug exposure, family history and so on.

‡IPF medical history includes the date of initial symptoms and whether an HRCT scan was taken, along with the date and associated examination results.

§Comorbidities refer to systemic conditions/diseases other than IPF, for example, diabetes, hyperlipidemia and gastrointestinal ulcers. The time of initial diagnosis and associated treatment for these conditions should be recorded.

¶Clinical features of IPF include chronic exertional dyspnoea, cough, bibasilar inspiratory velcro crackles on auscultation, digital clubbing, accompanying extrapulmonary manifestations and so on. mMRC dyspnoea score21 and GerdQ gastro-oesophageal reflux score22 should be evaluated and recorded.

**GAP score should be evaluated after lung function evaluation.23 24

††Fibrosis score from HRCT chest examination should be recorded.25

‡‡To obtain a definitive diagnosis, patients may require a bronchoscopy, including BAL and/or TBLB or BLC, which would be conducted or not depending on the clinical decision.

§§To obtain a definitive diagnosis, patients may require VATS or OLB, which would be conducted or not depending on the clinical decision.

¶¶AE-IPF is defined as (1) previous or simultaneous diagnosis of IPF; (2) typical acute dyspnoea symptoms or symptoms worsening within 30 days; (3) chest CT imaging pattern of usual interstitial pneumonia with new bilateral ground-glass opacities; and (4) symptoms cannot be completely explained by heart failure or fluid overload.

***Treatment details of IPF include the treatment plan, the type of drug, the dose, the start and end date and the outcome of the treatment, and the time of treatment change or addition of the drug. Treatments that are used in less than 2% of the study population would be grouped and analysed as a whole. Common treatments include, but are not limited to, pirfenidone, nintedanib, glucocorticoids, N-acetylcysteine, azithromycin, cyclophosphamide, azathioprine or other immunosuppressants, antiplatelet drugs, anticoagulants, anti-reflux drugs, anti-pulmonary hypertension drugs, airway drugs and Chinese medicine/proprietary Chinese medicine. Adverse reactions associated with IPF treatments should be specified.

†††Non-pharmacological treatments include long-term oxygen therapy, mechanical ventilation, pulmonary rehabilitation, lung transplantation and so on.

‡‡‡Changes in the patient’s conditions include clinical improvement, disease progression or death. The cause and time of death should be recorded. Patients should be followed for the full 3-year period as per study design or until death, whichever occurs first. Survival status data will be used for mortality analysis.

§§§Clinical events of concern include AE-IPF, hospitalisation, lung transplantation, pulmonary infections, respiratory failure, pulmonary hypertension, pulmonary embolism, lung cancer, acute myocardial infarction, stroke, other arterial embolism, deep vein thrombosis, haemorrhage, gastrointestinal perforation and other diseases that impact the prognosis of patients.

¶¶¶IPF-related costs include direct medical costs (hospitalisation costs, outpatient/emergency visits, including laboratory tests, imaging studies, medications and non-pharmacological treatments).

****Evaluation of patient-reported outcomes includes SGRQ22 and HADS.26 27

††††Blood samples, including serum, plasma and buffy coat cells, should be collected within the first year of follow-up; further sample collection after the first year of follow-up is not required.

‡‡‡‡BALF specimens from bronchoscopy should be collected.

§§§§If a surgical lung biopsy is performed, lung tissue specimens should be collected.

AE-IPF, acute exacerbations of IPF; BAL, bronchoalveolar lavage; BALF, bronchoalveolar lavage fluid; BLC, bronchoscopic lung cryobiopsy; FU, follow-up; GAP, gender–age–physiology; GerdQ, Gastro-oesophageal Reflux Disease Questionnaire; HADS, Hospital Anxiety and Depression Scale; HRCT, high-resolution CT; IPF, idiopathic pulmonary fibrosis; mMRC, modified medical research council; OLB, open-lung biopsy; SGRQ, St. George's Respiratory Questionnaire; TBLB, transbronchial lung biopsy; VATS, video-assisted thoracoscopic surgery.