Can home spirometry and FeNO testing improve asthma diagnosis? a feasibility study

IntroductionAlthough temporal variation is the hallmark of asthma, recommended diagnostic approaches largely rely on single clinic-based measurements. Ambulatory monitoring captures diurnal and day-to-day variability and may therefore enhance diagnostic accuracy. We evaluated the clinical feasibility and potential utility of home spirometry and fractional exhaled nitric oxide (FeNO) monitoring in asthma diagnosis. MethodsSymptomatic, untreated adults with GP-suspected asthma underwent diagnostic tests including bronchodilator reversibility, in-clinic FeNO, blood eosinophil counts and bronchial challenge. Participants measured spirometry and FeNO four times daily over one week; during the second week spirometry were measured twice daily. The reference standard was provided (asthma/not-asthma) by an expert panel of at least two asthma specialists based on clinical history and the results of all in-clinic testing; home spirometry (except for peak expiratory flow) and FeNO measurements were blinded to the panel. ResultsOf 67 eligible participants, 51(76%) were recruited, and 38 had asthma confirmed or excluded by the panel. 1058 home spirometry measurements were obtained from 37(73%) participants; 848 home FeNO readings were obtained from 39(76%) participants. Among those completing at least one home measurement, median (IQR) adherence was 66.7(58.6-97.6)% for spirometry and 78.5(51.8-103.6)% for FeNO. Collection of health impact data for economic evaluation was feasible. In participants with a confirmed diagnostic outcome who completed home measurements (FeNO: n=32; spirometry: n=28), the putative home-testing metrics demonstrated high sensitivities at [≥]90% specificity, and outperformed peak expiratory flow diurnal variability. Incorporating home testing into the BTS/NICE/SIGN 2024 diagnostic pathway had the potential to reduce reliance on bronchial challenge testing by 57%. ConclusionsHome spirometry and FeNO testing and the prospective collection of health-economic data in the diagnostic setting were feasible. Home-based testing strategy showed early potential to improve asthma diagnosis and pathway efficiency. These findings support further evaluation through an adequately powered diagnostic accuracy study and health-economic assessment. Key messagesO_LIWhat is already known on this topic: Asthma can be difficult to diagnose, as objective tests may be normal when assessments are performed during periods of minimal or intermittent symptoms. C_LIO_LIWhat this study adds: Our data suggest that home spirometry and FeNO monitoring could be successfully implemented within a diagnostic accuracy trial. Participants were able to perform these tests reliably in the home environment. C_LIO_LIHow this study might affect research, practice or policy: The early findings suggest that home-based physiological monitoring may offer additive diagnostic value beyond standard clinic-based assessments and could reduce reliance on bronchial challenge testing. These results provide a clear rationale for larger diagnostic accuracy trials and for undertaking early health-economic modelling to assess the potential impact on clinical pathways and resource utilisation. C_LI