Development and validation of a parent proxy bronchiectasis child quality of life instrument: The BC-QoL

Background: Quality of life (QoL), the highest prioritised outcome by children with bronchiectasis and their parents, is a patient-reported outcome measure increasingly considered essential when evaluating health and interventions. Despite this, there are no validated instruments that specifically measure QoL related to bronchiectasis in children. We aimed to develop and validate a new bronchiectasis child-specific parent-proxy QoL instrument (BC-QoL). Methods: We developed a draft 44-item BC-QoL and subsequently conducted a prospective cohort study where 142 parents completed draft BC-QoL and six other measures: two validated cough scores, parent-proxy children's acute cough-specific QoL, depression, anxiety and stress 21-item scale, RAND-36 and paediatric QoL (PedsQLTM4.0) to assess the convergent and discriminant validity of the BC-QoL. The questionnaires were completed over three weeks at different phases of their child's illness (stable state, exacerbation and/or recovery). Responses were analysed using psychometric and clinical impact techniques to reduce items and determine the instrument's reliability and validity. Minimally important difference (MID) was also calculated. Results: The final 23-item BC-QoL instrument with its three domains (emotional, physical, social well-being) demonstrated high split half reliability (0.95), Cronbach's alpha (0.97), repeatability (intraclass coefficient=0.74, 95%CI 0.62-0.82), validity and responsiveness. BC-QoL's domains significantly correlated with that of PedsQLTM4.0 (Spearman correlations: emotional=0.43, social=0.41, physical=0.47). BC-QoL's MID ranged from 0.74 to 1.32. Conclusion: BC-QoL, the first bronchiectasis child-specific QoL instrument, has evidence demonstrating its validity and reliability, and can be used to evaluate the impact and effectiveness of interventions and better understand the disease burden in children with bronchiectasis.