Gender and age affect the levels of exhaled nitric oxide in healthy children

Asthma is a chronic inflammatory disorder of the lung and diagnosis is difficult in children. The measurement of fractional exhaled nitric oxide (FeNO) may be useful in the diagnosis and monitoring of treatments. A number of factors affect FeNO levels and their influence varies across countries and regions. This study included 300 healthy students, aged from 6 to 14 years, who participated voluntarily. A comprehensive medical survey was used and measurements of FeNO levels and spirometric parameters were recorded in Shenyang, China. We observed that the median FeNO was 11 ppb (range, 8-16 ppb) in children from the northern areas of China. For males, the median level was 13 ppb (range, 9-18 ppb) and the median level was 10 ppb (range, 8-14 ppb) for females. There was a significant difference between males and females (P= 0.007) and age was correlated with FeNO (R²= 0.6554), while weight, height, body mass index (BMI), forced vital capacity (FVC), forced expiratory volume (FEV1), FEV1/FVC and peak expiratory flow (PEF) had no correlation with FeNO. In conclusion, the median FeNO is 11 ppb (range, 8-16 ppb) in male and female healthy children from northern areas of China and is affected by gender and age.