title: Reference values and determinants of fractional concentration of exhaled nitric oxide in healthy children.
abstract: OBJECTIVE
  Measurement of the fractional concentration of exhaled nitric oxide (FeNO) is a quantitative, noninvasive, simple, safe method of assessing airway inflammation. While FeNO measurement has been standardized, reference values for elementary school children are scarce. The aim of this study was to establish reference values for FeNO in children.
  
  
  METHODS
  FeNO was measured in elementary school children at 6-12 years of age in Seoul, Korea, following American Thoracic Society guidelines and using a chemiluminescence analyzer (NIOX Exhaled Nitric Oxide Monitoring System, Aerocrine, Sweden). A total of 1,252 children completed a modified International Study of Asthma and Allergy in Children (ISAAC) questionnaire; FeNO was measured in 1,063 children according to the protocol and in 808 children defined as healthy controls.
  
  
  RESULTS
  Mean FeNO were 10.32 ppb, 16.58 ppb, and 12.36 ppb in non-atopic, atopic, and all 808 healthy controls, respectively. FeNO was not associated with age and gender. The FeNO reference equations were determined by multiple linear regression analysis, taking into account the variables of age, height, weight, total IgE, eosinophil percent, and bronchial hyper-responsiveness (methacholine PC20). FeNO=0.776+0.003×total IgE+0.340×eosinophil percent; coefficient of determination (R2)=0.084 in the 501 healthy non-atopic controls. FeNO=-18.365+1.536×eosinophil percent, R2=0.183 in the 307 healthy atopic controls; and FeNO=-7.888+0.130×Height+0.004×total IgE+1.233×eosinophil percent, R2=0.209 in the 808 all healthy controls. Eosinophil percent was correlated with FeNO in all healthy controls. FeNO was not associated with BMI.
  
  
  CONCLUSIONS
  This study provides reference values for FeNO that can be used to evaluate airway inflammation in elementary school children. Determinants that could most accurately predict FeNO in healthy school-age children were assessed.
authors.affiliation: Department of Pediatrics, Childhood Asthma Atopy Center, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea.
authors.forename: Hyun-Ju
authors.initials: HJ
authors.lastname: Cho
authors.affiliation: Department of Pediatrics, CHA University School of Medicine, Seongnam, Korea. ; Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Jung
authors.affiliation: Department of Pediatrics, Childhood Asthma Atopy Center, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea. ; Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Song-I
authors.initials: SI
authors.lastname: Yang
authors.affiliation: Department of Pediatrics, Childhood Asthma Atopy Center, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea. ; Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Eun
authors.initials: E
authors.lastname: Lee
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Kosin University Gospel Hospital, Kosin University College of Medicine, Busan, Korea.
authors.forename: Hyung Young
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Korea Cancer Center Hospital, Seoul, Korea.
authors.forename: Ju-Hee
authors.initials: JH
authors.lastname: Seo
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Kwon
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Byoung-Ju
authors.initials: BJ
authors.lastname: Kim
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Hyo-Bin
authors.initials: HB
authors.lastname: Kim
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea.
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Dae Jin
authors.initials: DJ
authors.lastname: Song
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Seoul Paik Hospital, Inje University College of Medicine, Seoul, Korea.
authors.forename: Woo Kyung
authors.initials: WK
authors.lastname: Kim
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, National Health Insurance Corporation Ilsan Hospital, Seoul, Korea.
authors.forename: Gwang Cheon
authors.initials: GC
authors.lastname: Jang
authors.affiliation: Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Department of Pediatrics, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jung Yeon
authors.initials: JY
authors.lastname: Shim
authors.affiliation: Department of Pediatrics, Childhood Asthma Atopy Center, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea. ; Research Center for Standardization of Allergic Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Soo-Jong
authors.initials: SJ
authors.lastname: Hong
keywords: FeNO; children; determinants; healthy; reference value