The comparison of two exhaled nitric oxide analyzers: NIOX VERO and SUNVOU-CA2122

As a marker of eosinophilic airway inflammation, fractional exhaled nitric oxide (FeNO) was widely used in clinical practice. NIOX VERO (VERO) and SUNVOU-CA2122 (CA2122) are two commonly used eNO analyzers in China. However, what's the difference and agreement between the two devices and whether the two types of devices can be replaced by each other in the application of common respiratory diseases have not been reported. The purpose of this study was to compare the two types of devices and to evaluate the difference between them in clinical use and whether they could be replaced. FeNO levels in 244 respiratory patients (including asthma, chronic obstructive pulmonary disease, chronic cough) were measured by CA2122 analyzer and VERO analyzer, respectively. The FeNO values obtained by the two devices were compared and the differences were analyzed. The success rate, the number of attempts and the total time required for a successful measurement by CA2122 and VERO were compared. The FeNO values measured by CA2122 online and offline were also compared. FeNO values obtained by CA2122 were slightly higher than those of VERO [median(range): 29.0(9-271) parts per billion (ppb) vs 25.5 (5-263) ppb,P= 0.000]. There was a high correlation between FeNO values measured by the two types of devices (r= 0.964,P= 0.000). By comparison, there was a high degree of agreement between the FeNO values measured by two devices, in all patients with different respiratory diseases. FeNO values measured online and offline by CA2122 were highly correlated and there was a high degree of agreement between online and offline methods. The success rate of CA2122 was higher than VERO, and the number of attempts (2.1 vs 2.4) and the total time (110.5 ± 35.7 vs 117.5 ± 48.1 s) required for a successful measurement by CA2122 were lower than those of VERO. CA2122 and VERO can be replaced by each other, and FeNO values can be converted if necessary. CA2122 has some advantages in success rate, the mean attempts and time required for successful measurement of FeNO.