At-home hand-held spirometers unreliable in adolescent cystic fibrosis monitoring

Remote monitoring would be ideal for patients with cystic fibrosis, but a study presented at the North American Cystic Fibrosis Conference showed a wide variety in reliability and accuracy.

“Traditionally, young people with cystic fibrosis are seen routinely in clinic every 2 to 3 months regardless of their clinical severity, which means that they miss significant amount of school, parents miss work and they sometimes travel long distances to get to clinic,” Claire Edmondson, MBChB, clinical research fellow at Imperial College London, said in her presentation. “The COVID-19 pandemic meant clinics had to rapidly change how they deliver care and one way they may have done that is to give young people readily available hand-held spirometers, but are these hand-held spirometers equivalent to our clinic spirometers?”

Edmondson and colleagues designed an application incorporating data capture from a Bluetooth-enabled spirometer and provided it to children aged at least 5 years. The patients were trained and instructed to record values at least twice weekly.

Patients maintained their scheduled clinic visits through the 6 months of the study for researchers to compare FEV₁ from clinic visits in which they were supervised with those obtained unsupervised at home within the same time frame.

“We tested four spirometers on 4 separate days in triplicate and all spirometers underread at the 1 L volume,” Edmondson said. “The maximum underread was 0.08 L, and while that doesn’t sound like much in raw liters value, when I converted it to a theoretical child, it could account for an 8% difference in their FEV₁.”

Median FEV₁ percent values were different between clinic (90.4%; 95% CI, 80.4-100.6) and home (85.4%; 95% CI, 70.7-93.8; P < .0001). Values from the two devices correlated (r² = 0.85; P < .001), but there was substantial bias with higher clinic values from 51 participants (77.6%). Mean difference between clinic and home FEV₁ was 6.5 ± 8.2% with limits of agreement of –9.6% to 22.7%. This bias remained but was less marked in the subgroup of patients aged at least 12 years (3.8 ± 8.9%; limits of agreement, –13.6%-21%).

“We’ve shown that the unsupervised use of hand-held spirometers leads to significantly lower levels than those achieved while supervised in clinic,” Edmondson said. “We would suggest that prior to implementing this technology in your young people with cystic fibrosis, we should carry out a rigorous assessment of the technology and look at how we could supervise their usage at home to ensure we are using the data to the best of its ability.”