RT Journal Article SR Electronic T1 Protocol for CLASSIC PBB: comparison of lower airway sampling strategies in children with protracted bacterial bronchitis JF BMJ Paediatrics Open JO BMJ Paediatrics Open FD BMJ Publishing Group Ltd SP e001722 DO 10.1136/bmjpo-2022-001722 VO 6 IS 1 A1 Gilchrist, Francis J A1 Aspey, Mathew A1 Bowler, Robert A1 Brodlie, Malcolm A1 Desai, Seema A1 Harris, Caroline A1 Hinton, Emily A1 Kulkarni, Hemant A1 Ogbolosingha, Aviva A1 Sinha, Ian A1 Solis-Trapala, Ivonne A1 Stock, Joanne A1 Carroll, William D YR 2022 UL http://bmjpaedsopen.bmj.com/content/6/1/e001722.abstract AB Background Protracted bacterial bronchitis (PBB) is an endobronchial infection and a the most common cause of chronic wet cough in young children. It is treated with antibiotics, which can only be targeted if the causative organism is known. As most affected children do not expectorate sputum, lower airway samples can only be obtained by bronchoalveolar lavage (BAL) samples taken during flexible bronchoscopy (FB-BAL). This is invasive and is therefore reserved for children with severe or relapsing cases. Most children with PBB are treated empirically with broad spectrum antibiotics. CLASSIC PBB will compare the pathogen yield from two less invasive strategies with that from FB-BAL to see if they are comparable.Methods 131 children with PBB from four UK centres referred FB-BAL will be recruited. When attending for FB-BAL, they will have a cough swab and an induced sputum sample obtained. The primary outcome will be the discordance of the pathogen yield from the cough swab and the induced sputum when compared with FB-BAL. Secondary outcomes will be the sensitivity of each sampling strategy, the success rate of the induced sputum in producing a usable sample and the tolerability of each of the three sampling strategies.Discussion If either or both of the two less invasive airway sampling strategies are shown to be a useful alternative to FB-BAL, this will lead to more children with PBB having lower airway samples enabling targeted antibiotic prescribing. It would also reduce the need for FB, which is known to be burdensome for children and their families.Trial registration number ISRCTN79883982.No data are available.