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 (R(2)= 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.