Unsupervised home spirometry versus supervised clinic spirometry: analysis of longitudinal participant-level data from the CLEAR trial in patients with bronchiectasis

Background Lung function measurement is central to assessing disease severity and monitoring progression in bronchiectasis. Although home spirometry is convenient for remote monitoring, there is limited evidence for its performance. Aims In an a priori defined substudy in the CLEAR trial (a multicentre, randomised, open-label study of hypertonic saline and carbocisteine versus usual care in bronchiectasis), we assessed the performance of home spirometry in adults with bronchiectasis using the PANACEA framework (seven domains: test Performance, disease mANAgement, Cost, patient Experience, clinician Experience, researcher Experience, and Access). Methods Participants performed supervised ‘clinic’ spirometry at five visits and unsupervised ‘home’ spirometry weekly and during exacerbations over 52 weeks. Analyses evaluated agreement, longitudinal variation, changes in lung function across exacerbations, measurement quality, adherence and patient experience. Agreement was evaluated using Bland-Altman analysis; other outcomes were summarised descriptively. Results 257 participants had home spirometry data. Clinic and home spirometry demonstrated close agreement, with a mean forced expiratory volume in 1 s (FEV 1 ) difference of 20 mL (95% CI −130 to 170). Variability decreased over time (coefficient of variation 12.25% to 8.81%). Among 462 exacerbations, 195 had spirometry data within 7 days of exacerbation start/end dates. A >100 mL decline in FEV 1 occurred in 48% of exacerbations; 35% returned to within 100 mL of pre-exacerbation stable values by exacerbation end. Most spirometry sessions met American Thoracic Society/European Respiratory Society quality criteria, adherence declined over time while patient experience was generally positive. Conclusion Home spirometry demonstrates good agreement with clinic spirometry, with variability between measurements decreasing over time. Home spirometry detected changes in lung function across exacerbations, although variability may limit interpretation at the individual patient level. With appropriate patient support to maintain adherence, home spirometry has potential as a tool for remote monitoring and decentralised clinical trials in bronchiectasis. Trial registration number ISRCTN89040295 .