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Comparison of Lower Airway Sampling Strategies in Children with Protracted Bacterial Bronchitis (CLASSIC-PBB): a
Francis J Gilchrist1,2, Ivonne Solis-Trapala2, Mathew Aspey3
1Department of Paediatric Respiratory Medicine, University Hospitals of North Midlands NHS Trust, Stoke-on-Trent, UK francis.gilchrist@uhnm.nhs.uk.
Insights
Cough swabs and induced sputum are not reliable alternatives to flexible bronchoscopy with bronchoalveolar lavage (FB-BAL) for diagnosing protracted bacterial bronchitis (PBB) in children. Induced sputum may be useful for early assessment in select cases.
Area of Science:
- Pediatric Pulmonology
- Microbiology
- Diagnostic Accuracy
Background:
- Protracted bacterial bronchitis (PBB) is a primary cause of chronic wet cough in children.
- Accurate pathogen identification is crucial for effective antibiotic stewardship.
- Flexible bronchoscopy with bronchoalveolar lavage (FB-BAL) is the current gold standard for PBB diagnosis.
Purpose of the Study:
- To evaluate the diagnostic accuracy of cough swabs (CS) and induced sputum (IS) as alternatives to FB-BAL for identifying pathogens in children with PBB.
- To compare the microbiological yield and discordance rates of CS and IS against various FB-BAL sampling strategies (BAL1, BAL2, BAL6).
Main Methods:
- Prospective study involving children with PBB undergoing FB-BAL.
- Collection of concurrent CS and IS samples from participants.
- Assessment of microbiological discordance between CS/IS and different FB-BAL volumes (BAL1, BAL2, BAL6).
Main Results:
- Pathogen detection rates: CS 22%, IS 60%, BAL6 78%.
- High discordance observed between CS/IS and BAL6 (74% and 71%, respectively).
- CS had a 67% false negative rate, while IS had a 27% false negative rate compared to BAL6.
Conclusions:
- Neither CS nor IS are viable alternatives to FB-BAL for diagnosing PBB due to high discordance.
- Induced sputum, despite limitations, may be considered for initial PBB assessment in children not requiring FB-BAL, owing to its tolerability and lower false negative rate.
Background:
Protracted bacterial bronchitis (PBB) is a leading cause of paediatric chronic wet cough. Identifying the causative pathogen promotes antibiotic stewardship, but bronchoalveolar lavage taken during flexible bronchoscopy (FB-BAL) is the only validated sampling strategy. We prospectively investigated if cough swab (CS) or induced sputum (IS) was a viable alternative.
Methods:
Children with PBB, referred for FB-BAL, provided a cough swab and induced sputum. Discordance in microbiological yield (failure to identify identical pathogens) between cough swab and BAL, and between induced sputum and BAL was assessed. This was performed for single-lobe (BAL1), two-lobe (BAL2) and six-lobe BAL (BAL6).
Results:
135 underwent FB-BAL, 134 produced a cough swab and 111 an induced sputum sample. 30 (22%) cough swab, 67 (60%) induced sputum and 101 (78%) BAL6 were pathogen positive. cough swab/BAL6 discordance was seen in 74% with a discordance OR (95% CI) for cough swab-BAL6+ versus cough swab+BAL6- of 30.3 (9.6 to 95.8). induced sputum/BAL6 discordance was seen in 71% with a discordance OR (95% CI) for induced sputum-BAL6+ versus induced sputum+BAL6- of 4.2 (2.4 to 7.4). The ability of each sampling strategy to identify all pathogens from cough swab, induced sputum and BAL6 was: cough swab 17%, induced sputum 38%, BAL1 40%, BAL2 53% and BAL6 78%. The false negative rates were: cough swab 67%, induced sputum 27%, BAL1 33%, BAL2 16% and BAL6 9%.
Conclusions:
The pathogen yield of both cough swab and induced sputum had high discordance with BAL6, meaning neither is a viable alternative to FB-BAL. However, the tolerability and relatively low false negative rate of induced sputum mean it can be part of early PBB assessment in children who do not warrant FB-BAL.
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