title: Utility of fractional exhaled nitric oxide (F(E)NO) measurements in diagnosing asthma.
abstract: BACKGROUND
  To facilitate the use of fractional exhaled nitric oxide (F(E)NO) as a clinical test, F(E)NO measurements need more clarification.
  
  
  OBJECTIVE
  We sought to evaluate the yield of F(E)NO measurement for the diagnosis of asthma and identify the determinants of F(E)NO in children.
  
  
  METHODS
  Two hundred forty five consecutive steroid-naïve patients aged 8-16 years with symptoms suggestive of asthma were included. Children were evaluated using F(E)NO measurements, questionnaires, skin prick tests, spirometries, and methacholine challenge tests.
  
  
  RESULTS
  Asthma was diagnosed in 167 children. The sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of F(E)NO measurements for the diagnosis of asthma at the best cutoff value of 22 ppb were 56.9%, 87.2%, 90.5%, and 48.6%, respectively. At a cutoff value of 42 ppb, specificity and PPV were all 100% but at the cost of very low sensitivity (23.4%) and NPV (37.9%). Both atopy and asthma were identified as independent risk factors associated with high F(E)NO. The association of asthma with high F(E)NO was found only in atopic children because F(E)NO was low in non-atopic children regardless of asthma status. Although highest F(E)NO was observed in atopic asthmatic patients, 28% of these patients had F(E)NO values lower than 22 ppb.
  
  
  CONCLUSIONS
  Atopic asthmatic patients with low F(E)NO values and non-atopic asthmatic patients were responsible for false-negative cases that might contribute to low sensitivity of F(E)NO measurements in diagnosing asthma. High specificity of F(E)NO measurements may help identify patients with atopic asthma among subjects with respiratory symptoms.
authors.affiliation: Department of Pediatrics, College of Medicine and Medical Research Institute, Chungbuk National University, 410 SungBong-Ro, Heungdeok-gu, 361-763 Cheongju, Republic of Korea.
authors.forename: Sung-Il
authors.initials: SI
authors.lastname: Woo
authors.forename: Ji-Hyuk
authors.initials: JH
authors.lastname: Lee
authors.forename: Heon
authors.initials: H
authors.lastname: Kim
authors.forename: Jong-Won
authors.initials: JW
authors.lastname: Kang
authors.forename: Yong-Han
authors.initials: YH
authors.lastname: Sun
authors.forename: Youn-Soo
authors.initials: YS
authors.lastname: Hahn
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000175:diagnosis*; D001944:Breath Tests / Q000379:methods; D001985:Bronchial Provocation Tests / Q000379:methods; D016085:Bronchoconstrictor Agents; D002648:Child; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000378:metabolism; D008297:Male; D016210:Methacholine Chloride; D009569:Nitric Oxide / Q000378:metabolism*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012882:Skin Tests; D013147:Spirometry / Q000379:methods; D014797:Vital Capacity / Q000502:physiology
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D009569:Nitric Oxide