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Aims: Spirometry is used by many clinicians to monitor asthma in children but relatively little is understood about its variability over time. The aim of this study was to determine the variability of forced expiratory volume in 1 s (FEV 1 ) in children with symptomatically well-controlled asthma by applying three different methods of expressing change in FEV 1 over 3-month intervals., Methods: Data from five longitudinal studies of children with asthma which measured FEV 1 at 3-month intervals over 6 or 12 months were used. We analysed paired FEV 1 measurements when asthma symptoms were controlled. The variability of FEV 1 % predicted (FEV 1 %), FEV 1 z-score (FEV 1 z) and conditional z score for change (Zc) in FEV 1 was expressed as limits of agreement., Results: A total of 881 children had 3338 FEV 1 measurements on occasions when asthma was controlled; 5184 pairs of FEV 1 measurements made at 3-month intervals were available. Each unit change in FEV 1 z score was equivalent to a Zc 1.45 and an absolute change in FEV 1 % of 11.6%. The limits of agreement for change in FEV 1 % were -20 and +21, absolute change in FEV 1 z were -1.7 and +1.7 and Zc were -2.6 and +2.1. Regression to the mean and increased variability in younger children were present for change in FEV 1 % and FEV 1 z comparisons, but not Zc., Conclusion: Given the wide limits of agreement of paired FEV 1 measurements in symptomatically well-controlled children, asthma treatment should primarily be guided by symptoms and not by a change in spirometry., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Asthma guidelines guide health practitioners to adjust treatments to the minimum level required for asthma control. As many people with asthma have an eosinophilic endotype, tailoring asthma medications based on airway eosinophilic levels (sputum eosinophils or exhaled nitric oxide, FeNO) may improve asthma outcomes., Objective: To synthesise the evidence from our updated Cochrane systematic reviews, for tailoring asthma medication based on eosinophilic inflammatory markers (sputum analysis and FeNO) for improving asthma-related outcomes in children and adults., Data Sources: Cochrane reviews with standardised searches up to February 2017., Study Selection: The Cochrane reviews included randomised controlled comparisons of tailoring asthma medications based on sputum analysis or FeNO compared with controls (primarily clinical symptoms and/or spirometry/peak flow)., Results: The 16 included studies of FeNO-based management (seven in adults) and 6 of sputum-based management (five in adults) were clinically heterogeneous. On follow-up, participants randomised to the sputum eosinophils strategy (compared with controls) were significantly less likely to have exacerbations (62 vs 82/100 participants with ≥1 exacerbation; OR 0.36, 95% CI 0.21 to 0.62). For the FeNO strategy, the respective numbers were adults OR 0.60 (95% CI 0.43 to 0.84) and children 0.58 (95% CI 0.45 to 0.75). However, there were no significant group differences for either strategy on daily inhaled corticosteroids dose (at end of study), asthma control or lung function., Conclusion: Adjusting treatment based on airway eosinophilic markers reduced the likelihood of asthma exacerbations but had no significant impact on asthma control or lung function., Competing Interests: Competing interests: HLP, and ABC have conducted a randomised controlled trial in children on this subject. Other authors have no competing interests to declare., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: Quality of life (QoL) measures are an important patient-relevant outcome measure for clinical studies. Cough is the most common symptom that results in new medical consultations. Although adult and parent-proxy cough-specific QoL instruments have been shown to be a useful cough outcome measure, no suitable cough-specific QoL measure for children with chronic cough exists. We report on the statistical properties of a chronic cough-specific QoL (CC-QoL) questionnaire for children., Method: 130 children (median age 10 years, IQR 8-12 years; 65 girls) participated. A preliminary 37-item version was developed from conversations with children with chronic cough (>4 weeks). Children also completed generic QoL questionnaires (Pediatric QoL Inventory 4.0 (PedsQL4.0), Spence Children's Anxiety Scale (SCAS)) and cough diary scores., Results: The clinical impact method of item reduction resulted in 16 items that had excellent internal consistency (Cronbach's α=0.94) among these items and also within each domain. Evidence for construct and criterion validity was established with significant correlations between CC-QoL subscales with cough scores, PedsQL and SCAS scores. CC-QoL scores were sensitive to change following an intervention and significant differences were noted between those children coughing and those who had ceased coughing. Minimum important difference (MID) for overall and domain CC-QoL ranged from 0.37-1.36 (distribution-based approach) to 1.11-1.58 (anchor-based approach)., Conclusions: Chronic cough significantly impacts the QoL of children. The CC-QoL is a reliable, valid and sensitive to change outcome measure that assesses QoL from the child's perspective. Pending data from a confirmatory cohort, a MID for the CC-QoL of 1.1 is recommended when evaluating health status change., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)