title: Exhaled nitric oxide in a population-based study of southern California schoolchildren.
abstract: BACKGROUND
  Determinants of exhaled nitric oxide (FeNO) need to be understood better to maximize the value of FeNO measurement in clinical practice and research. Our aim was to identify significant predictors of FeNO in an initial cross-sectional survey of southern California schoolchildren, part of a larger longitudinal study of asthma incidence.
  
  
  METHODS
  During one school year, we measured FeNO at 100 ml/sec flow, using a validated offline technique, in 2568 children of age 7-10 yr. We estimated online (50 ml/sec flow) FeNO using a prediction equation from a separate smaller study with adjustment for offline measurement artifacts, and analyzed its relationship to clinical and demographic characteristics.
  
  
  RESULTS
  FeNO was lognormally distributed with geometric means ranging from 11 ppb in children without atopy or asthma to 16 ppb in children with allergic asthma. Although effects of atopy and asthma were highly significant, ranges of FeNO for children with and without those conditions overlapped substantially. FeNO was significantly higher in subjects aged > 9, compared to younger subjects. Asian-American boys showed significantly higher FeNO than children of all other sex/ethnic groups; Hispanics and African-Americans of both sexes averaged slightly higher than non-Hispanic whites. Increasing height-for-age had no significant effect, but increasing weight-for-height was associated with decreasing FeNO.
  
  
  CONCLUSIONS
  FeNO measured offline is a useful biomarker for airway inflammation in large population-based studies. Further investigation of age, ethnicity, body-size, and genetic influences is needed, since they may contribute to substantial variation in FeNO.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. linn@usc.edu
authors.forename: William S
authors.initials: WS
authors.lastname: Linn
authors.forename: Edward B
authors.initials: EB
authors.lastname: Rappaport
authors.forename: Kiros T
authors.initials: KT
authors.lastname: Berhane
authors.forename: Tracy M
authors.initials: TM
authors.lastname: Bastain
authors.forename: Edward L
authors.initials: EL
authors.lastname: Avol
authors.forename: Frank D
authors.initials: FD
authors.lastname: Gilliland
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis* / Q000453:epidemiology*; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D002140:California / Q000453:epidemiology; D002648:Child; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009569:Nitric Oxide / Q000032:analysis*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013334:Students / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D009569:Nitric Oxide