Adherence to home spirometry among patients with IPF: results from the INMARK trial

Introduction: Frequent home spirometry may offer advantages over intermittent clinic spirometry in patients with IPF by providing a more accurate estimate of lung function and enabling earlier detection of disease progression or acute exacerbations. However, poor adherence may limit feasibility.

Aim: To assess adherence to home spirometry in subjects with IPF in the INMARK trial.

Methods: Subjects with IPF and FVC ≥80% predicted were randomised to receive nintedanib or placebo for 12 weeks, followed by open-label nintedanib for 40 weeks. Subjects were asked to perform home spirometry at least once a week and ideally daily. Adherence was assessed as the number of weeks that a subject provided ≥1 home spirometry measurement divided by the number of weeks they were followed in the study. Analyses included all subjects who received ≥1 dose of trial medication.

Results: Among 346 subjects, the proportion of subjects with 100% adherence decreased over the trial but remained above 50% (Figure). Over 52 weeks, mean adherence was 86% and median adherence was 96%. The mean number of home spirometry measurements was 3.4 per subject per week.

Conclusions: In subjects with IPF and preserved FVC, adherence to home spirometry over 52 weeks decreased over time but remained at a level suggesting that home spirometry might have a role in monitoring lung function in patients with IPF in clinical trials and clinical practice.