Interest in at-home measurements of lung function is growing as the ongoing COVID-19 pandemic pushes more respiratory consultations to the virtual setting. However, in a study presented at the 2021 American Thoracic Society (ATS) International Conference, researchers have found that at-home spirometry produces conflicting data with clinic measurements. The study authors, led by Frances Gardiner, of GlaxoSmithKline, advised caution in using data collected at home to inform treatment decisions for patients with asthma.
The researchers used data from the phase III CAPTAIN study, which randomized adults with uncontrolled asthma despite inhaled corticosteroid/long-acting β2-agonist therapy to receive either once-daily FF/VI or FF/UMEC/VI. In this analysis, they evaluated the agreement between trough FEV1 and other spirometry measurements taken in clinic with a MasterScope device and measurements patients took at home using a peak flow meter.
They used the Bland-Altman method to assess agreement between clinic trough FEV1 and the average of the home trough FEV1 measurements collected on the same day and 2 days prior to the clinic measurement, at baseline and at Week 24 (post hoc analyses).
Among the more than 2,000 patients with a value for both clinic and home trough FEV1 at baseline and follow-up, “agreement between clinic and home trough FEV1 measurements was poor,” the authors reported. At baseline, the lower and upper limits of agreement were –812 mL and 943 mL, respectively. At week 24 these values were –771 mL and 980 mL, respectively. A total of 6% of patients had measurements that fell outside the limits of agreement at baseline and week 24.
“[These data suggest] that home spirometry performed with the AM3 device cannot be used as an alternative to clinic spirometry, and that caution should be exercised when using home spirometry data in research or clinical care,” the researchers concluded. However, they added that home spirometry may offer complementary information to clinic measurements.