Inclusion and exclusion criteria
| Inclusion criteria | Exclusion criteria |
| Aged 1–10 years | Diagnosis of bronchiectasis, cystic fibrosis or immunodeficiency |
| Have a clinical diagnosis of PBB | FB-BAL being performed for a therapeutic indication (ie, lobar collapse) rather than for lower airway |
| Referred for a clinically indicated FB-BAL | Non-English speaker where translation facilities are insufficient to guarantee informed consent |
| Parent/guardian willing and able to give fully informed consent | Is taking part in another interventional study |
| Willing and able to comply with the study procedures |
BAL, bronchoalveolar lavage; FB, flexible bronchoscopy; PBB, protracted bacterial bronchitis.