Background: Recent guidelines for the diagnosis of asthma in schoolchildren recommend the measurement of exhaled nitric oxide fraction (F₄₍₎) as part of the diagnostic algorithm. However, implementation may be hampered by the lack of F₄₍₎ devices that are affordable and usable in all healthcare settings. We aimed to compare the performance of two portable F₄₍₎ devices (Evernoa (EVE) and NObreath (NOB) ) to a stationary "gold standard" device (CLD 88 sp (CLD) ) in children. Methods: 106 children aged 6-17 years under investigation or monitoring for asthma underwent F₄₍₎ measurements using the three devices in randomised order. Results: All devices showed high repeatability across a wide F₄₍₎ range (2. 5-191. 9 ppb). Median (interquartile range) F ENO levels were significantly lower with the portable devices (20. 8 (9. 5-43. 5), 16 (9-36) and 22. 8 (13. 2-55. 2) ppb for NOB, EVE and CLD, respectively; p94%) at a cut-off level of 25 ppb but lower agreement for a cut-off of 35 ppb. EVE required a greater number of attempts compared to NOB and CLD to achieve two valid measurements. Conclusions: Both portable devices showed limited interchangeability with the gold standard, making them less applicable for research and disease monitoring purposes. However, good overall agreement at the European Respiratory Society cut-off level (25 ppb) suggests potential as a simple and convenient screening tool in clinical settings for initial asthma diagnosis.
Thanikkel et al. (Mon,) studied this question.