Background and objectives: Fractional exhaled nitric oxide (FeNO) has been developed as a useful marker for eosinophilic airway inflammation and is widely used in clinical practice due to its convenience and noninvasiveness. There are two NO analyzers commonly used in China: the Sunvou-CA2122 Analyzer (NOS) and the NIOX VERO Analyzer (NOV). However, the relationships between the two devices have not yet been reported. The aim of our study was to determine the correlation and differences in the FeNO levels measured by the two devices.
Methods: FeNO levels were measured by both NOS and NOV in 107 adult patients with asthma. The asthma control test (ACT) score and lung function were also evaluated. This study was registered in the Chinese Clinical Trial Registry (http://www.chictr.org.cn).
Results: NOS yielded generally higher FeNO values than NOV [median (range): 87.0 (16 ∼ 276) vs 58.0 (9 ∼ 228); p < .001], and the difference increased with increasing FeNO levels. There was a high degree of correlation between FeNO values obtained with both devices (rs = 0.878, p < .001). However, the Bland-Altman plot showed a low degree of agreement, with a mean difference of -0.16 between logFeNONOS and logFeNONOV (95% CI: -0.45 ∼ 0.14). The conversion equation was calculated as follows: logFeNONOS= 0.027 + 0.904× logFeNONOV.
Conclusion: This was the first report to compare FeNO levels measured by NOS and NOV, showing a strongly positive correlation and a low degree of consistency between the two devices. Further prospective studies are required to verify our conclusions and determine the validity of the equation.
Keywords: Asthma; NIOX VERO analyzer; Sunvou-CA2122 analyzer; airway inflammation; exhaled nitric oxide.