Standardised classification of the aetiology of bronchiectasis using an objective algorithm

a) Aetiology algorithm; b) aetiology results, clinician diagnosis and results after aetiological algorithm. ^#: Note these diagnoses can also be complications or co-morbidities (e.g. allergic bronchopulmonary aspergillosis (ABPA) can complicate existing bronchiectasis). HRCT: high-resolution computed tomography; BE: bronchiectasis; CBC: complete blood count; PFT: pulmonary function test; CTD: connective tissue disease; PCD: primary ciliary dyskinesia; CF: cystic fibrosis; CFTR-RD: cystic fibrosis transmembrane conductance regulator-related disease; A1ATD: α₁-antitrypsin deficiency; IBD: inflammatory bowel disease; YNS: yellow nail syndrome; DPB: diffuse panbronchiolitis; NTM: nontuberculous mycobacteria; TB: tuberculosis; COPD: chronic obstructive pulmonary disease; GORD: gastro-oesophageal reflux disease; ID: immunodeficiency.