title: High levels and gender difference of exhaled nitric oxide in Chinese schoolchildren.
abstract: BACKGROUND
  Exhaled nitric oxide (eNO) may represent a useful noninvasive marker of airway inflammation, but data on the reference population values in schoolchildren are limited. No reference eNO study in Asian children has been published.
  
  
  METHODS
  Levels of eNO in a sample of 531 schoolchildren aged 11-18 years recruited from five schools (three international schools) in Hong Kong were measured online by a chemiluminescence analyser according to ERS/ATS standard. Each student also completed an International Study of Asthma and Allergic disease in Childhood questionnaire.
  
  
  RESULTS
  Among the children without a physician's diagnosis of asthma or symptoms of wheeze, rhinitis and eczema, there were 258 Chinese and 33 Caucasians. In control Chinese children, the eNO level (median: interquantile range) was significantly higher (P<0.001) in males (17.0 parts per billion (p.p.b.); 10.7-36.6) than in females (10.8 p.p.b.; 7.8-17.6). When compared with Caucasian control males (11.6 p.p.b.; 8.2-19.3) and females (9.1 p.p.b.; 7.5-11.9), the Chinese children had significantly higher eNO levels for both males (P=0.011) and females (P=0.037). For Chinese asthmatic males, the median eNO (interquartile range) was 39.8 p.p.b. (12.5-73.8), and for asthmatic females, 18.0 (9.6-56.3). After controlling for sex in Chinese controls, eNO did not have any significant correlation with height, weight and body mass index or body surface area.
  
  
  CONCLUSIONS
  This study demonstrates a gender difference of eNO level in healthy Chinese schoolchildren. When compared with Caucasians, Chinese children have significantly higher eNO levels.
authors: Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
authors: G W K
authors: GW
authors: Wong
authors: E K H
authors: EK
authors: Liu
authors: T F
authors: TF
authors: Leung
authors: E
authors: E
authors: Yung
authors: F W S
authors: FW
authors: Ko
authors: D S C
authors: DS
authors: Hui
authors: T F
authors: TF
authors: Fok
authors: C K W
authors: CK
authors: Lai
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000208:ethnology / Q000503:physiopathology*; D015992:Body Mass Index; D049628:Body Size / Q000502:physiology; D002648:Child; D005260:Female; D006723:Hong Kong / Q000208:ethnology; D006801:Humans; D006967:Hypersensitivity / Q000208:ethnology / Q000503:physiopathology; D008297:Male; D009569:Nitric Oxide / Q000032:analysis*; D011159:Population Surveillance / Q000379:methods; D012119:Respiration; D012737:Sex Factors
chemical_list: D009569:Nitric Oxide