Abstract
BACKGROUND: Patients with interstitial lung disease (ILD) require regular physician visits and referral to specialist ILD clinics. Difficulties or delays in accessing care can limit opportunities to monitor disease trajectory and response to treatment, and the COVID-19 pandemic has added to these challenges. Therefore, home monitoring technologies, such as home handheld spirometry, have gained increased attention as they may help to improve access to care for patients with ILD. However, while several studies have shown that home handheld spirometry in ILD is acceptable for most patients, data from clinical trials are not sufficiently robust to support its use as a primary endpoint. This review discusses the challenges that were encountered with handheld spirometry across three recent ILD studies, which included home spirometry as a primary endpoint, and highlights where further optimisation and research into home handheld spirometry in ILD is required. Rate of decline in forced vital capacity (FVC) as measured by daily home handheld spirometry versus site spirometry was of primary interest in three recently completed studies: STARLINER (NCT03261037), STARMAP and a Phase II study of pirfenidone in progressive fibrosing unclassifiable ILD (NCT03099187). Unanticipated practical and technical issues led to problems with estimating FVC decline. In all three studies, cross-sectional correlations for home handheld versus site spirometry were strong/moderate at baseline and later timepoints, but longitudinal correlations were weak. Other issues observed with the home handheld spirometry data included: high within-patient variability in home handheld FVC measurements; implausible longitudinal patterns in the home handheld spirometry data that were not reflected in site spirometry; and extreme estimated rates of FVC change. CONCLUSIONS: Home handheld spirometry in ILD requires further optimisation and research to ensure accurate and reliable FVC measurements before it can be used as an endpoint in clinical trials. Refresher training, automated alerts of problems and FVC changes, and patient support could help to overcome some practical issues. Despite the challenges, there is value in incorporating home handheld spirometry into clinical practice, and the COVID-19 pandemic has highlighted the potential for home monitoring technologies to help improve access to care for patients with ILD.