Predictors of 'frequent exacerbator' Phenotype in children with bronchiectasis: The first report on children from the Australian Bronchiectasis Registry.

Introduction/Aim: Current descriptions of paediatric cohorts with bronchiectasis are largely limited to single centres. In adults with bronchiectasis, the 'frequent exacerbator (FE)' phenotype has been defined but there is no such paediatric data yet. We used the paediatric data from the Australian Bronchiectasis Registry (ABR) to determine if a paediatric FE phenotype could be determined. We also described baseline characteristics in a large Australian-wide cohort. Method(s): We analysed the data of paediatric patients with radiologically confirmed bronchiectasis using the ABR's centralized database. Result(s): From March 2016-March 2020, 540 children [241 female; 288 Indigenous; median age 8 years (IQR 6-11)], were enrolled from 5 sites. The aetiology was considered post-infectious in 70% of children (5 post pulmonary tuberculosis), with 34% having had bronchiectasis for >5 years. Most had cylindrical bronchiectasis; 8 had cystic changes. Spirometry was available only in 24% of the cohort; median FEV1 z-score -0.74 (IQR -1.7 to -0.05), FVC z-score -0.37(-1.2 to 0.29), 24(18%) were obstructive. Indigenous children were significantly more likely to have environmental tobacco smoke exposure (84% vs 32%, p<0.0001), and lower birth weight (2797 g vs 3260 g, p<0.0001), and less likely to have primary ciliary dyskinesia (0.3% vs 6%, p<0.001). Children with FE phenotype, comprising a third of the cohort, were likely to be younger with more recent diagnosis of bronchiectasis and more likely to have been hospitalization in the previous 12 months (adjusted OR 4.4; p<0.001). The FE phenotype were also associated with higher likelihood of P. aeruginosa infection (adjusted OR 2.2;p=0.05) but were less likely to be Indigenous (adjusted OR 0.28;p<0.001). Conclusion(s): The largest cohort of Australian children with bronchiectasis has been described. PsA infection and previous hospitalization predicted FE phenotype whilst increased duration since diagnosis and older age reduced th