Measurement of Exhaled Nitric Oxide in Children: A Comparison Between NObreath® and NIOX VERO® Analyzers

Purpose: Few studies have compared fractional exhaled nitric oxide (FeNO) measurement by NIOX VERO (R) (NOV) and other devices in children. Moreover, there is no agreement between differences in FeNO values obtained using different devices in adults. Here, we compared FeNO values obtained using NOV and NObreath (R) (NOB) systems to derive a correction equation for children. Methods: Eighty-eight participants (age 7-15 years) who were diagnosed with atopic bronchial asthma and visited Sagamihara National Hospital as outpatients between January and April of 2017 were included. We measured FeNO values obtained using NOB and NOV, and analyzed them using Wilcoxon tests and Altman-Bland plots. Results: The median age of the participants was 11.5 years, and the scored Asthma Control Test (ACT) or Childhood ACT (C-ACT) was 25 (interquartile range, 24-25) or 26 (24-27). NOB and NOV values were significantly different (31 [14-52] versus 36 [20-59] ppb; P= 0.020) and strongly correlated (r= 0.92). An equation to convert NOB values into NOV values was derived using linear regression as follows: log NOV = 0.7329 x log NOB + 0.4704; NOB for 20, 40, 58, 80 and 100 ppb corresponded to NOV for 27, 44, 59, 73 and 86 ppb. Thus, NOB < 58 ppb suggested NOB < NOV, whereas NOB > 58 ppb suggested NOB > NOV. Conclusions: NOB and NOV values were strongly correlated. Participants whose FeNO values were relatively low represented NOB < NOV, whereas those whose FeNO values were relatively high represented NOB > NOV.