DIFFERENCES IN FRACTION OF EXHALED NITRIC OXIDE VALUES MEASURED BY TWO HAND-HELDED ANALYZERS (NObreath® AND NIOX Vero®)

Measurement of Fractional Exhaled Nitric Oxide in Adults: Comparison of Two Different Analyzers (NIOX VERO and NObreath)

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a non-invasive marker for eosinophilic airway inflammation and a good predictor of response to corticosteroids. There is a need for a reliable and accurate measurement method, as FeNO measurements have been widely used in clinical practice. Our study aimed to compare two FeNO analyzers and derive a conversion equation for FeNO measurements in adults.

METHODS

We included 99 participants who had chief complaints of chronic cough and difficulty in breathing. The participants underwent concurrent FeNO measurement using NIOX VERO (Circassia AB) and NObreath (Bedfont). We compared the values of the two devices and analyzed their correlation and agreement. We then formulated an equation to convert FeNO values measured by NObreath into those obtained by NIOX VERO.

RESULTS

The mean age of the participants was 51.2±17.1 years, with a female predominance (58.6%). Approximately 60% of the participants had asthma. The FeNO level measured by NIOX VERO (median, 27; interquartile range [IQR], 15-45) was significantly lower than that measured by NObreath (median, 38; IQR, 22-58; p<0.001). There was a strong positive correlation between the two devices (r=0.779, p<0.001). Additionally, Bland-Altman plots and intraclass correlation coefficient demonstrated a good agreement. Using linear regression, we derived the following conversion equation: natural log (Ln) (NObreath)=0.728×Ln (NIOX VERO)+1.244.

CONCLUSION

The FeNO values of NIOX VERO and NObreath were in good agreement and had positive correlations. Our proposed conversion equation could help assess the accuracy of the two analyzers.

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^® (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^® (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 × 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.