title: Cutoff point for exhaled nitric oxide corresponding to 3% sputum eosinophils.
abstract: BACKGROUND
  The eosinophilic asthma phenotype (sputum eosinophils 3%) indicates a good response to corticosteroids and T(H)2 immunomodulators. Exhaled nitric oxide (FeNO) is rapidly measured by portable devices, and although it is not a selective marker of eosinophilic inflammation, several studies have demonstrated a strong correlation with it. We investigated which FeNO value was the best fit with 3% sputum eosinophils in asthma patients.
  
  
  METHODS
  We included 129 consecutive, nonsmoking asthmatics who underwent skin tests, FeNO quantification (NIOX MINO), spirometry, and induced sputum analysis and completed the Asthma Control Test questionnaire. Receiver operating characteristic curves were constructed, and logistic regression analysis was performed.
  
  
  RESULTS
  Symptoms were detected more frequently in the eosinophilic asthma group, as were higher airway obstruction and sensitivity to hypertonic saline. The FeNO cutoff point of 21 ppb was the best fit with 3% sputum eosinophilia. This value behaved better among corticosteroid-naïve patients (sensitivity, 97%; specificity, 58%; positive predictive value, 86%; negative predictive value, 88%) than among those receiving corticosteroids (sensitivity, 81%; specificity, 25%; positive predictive value, 74%; negative predictive value, 33%).
  
  
  CONCLUSIONS
  FeNO ≥ 21 ppb is associated with airway eosinophilia. In corticosteroid-naïve patients, FeNO < 21 ppb enables us to rule out airway eosinophilia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Alvarez-Puebla
authors.forename: J M
authors.initials: JM
authors.lastname: Olaguibel Rivera
authors.forename: E
authors.initials: E
authors.lastname: Almudevar
authors.forename: A A
authors.initials: AA
authors.lastname: Echegoyen
authors.forename: B
authors.initials: B
authors.lastname: de Esteban Chocarro
authors.forename: K
authors.initials: K
authors.lastname: Cambra
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D002648:Child; D003430:Cross-Sectional Studies; D004804:Eosinophils / Q000276:immunology*; D045853:Exhalation; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D016015:Logistic Models; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D010641:Phenotype; D011237:Predictive Value of Tests; D011657:Pulmonary Eosinophilia / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D012372:ROC Curve; D012882:Skin Tests; D013147:Spirometry; D013183:Sputum / Q000276:immunology*; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D015415:Biomarkers; D018836:Inflammation Mediators; D009569:Nitric Oxide