title: Significance of fractional exhaled nitric oxide in chronic eosinophilic pneumonia: a retrospective cohort study.
abstract: BACKGROUND
  Chronic eosinophilic pneumonia (CEP) is characterized by chronic eosinophilic infiltration of the lung. It is dramatically responsive to corticosteroid treatment, but symptoms and radiopacities recur frequently after tapering or discontinuing the medication. Fractional exhaled nitric oxide (FeNO) is a well-known noninvasive marker of eosinophilic airway inflammation. The aim of this retrospective cohort study was to investigate the relationships of FeNO with peripheral eosinophilia and the clinical state of CEP and its validity for predicting exacerbation of CEP.
  
  
  METHODS
  Standard clinical and laboratory parameters, peripheral eosinophil percentage and count, and FeNO level were measured in 18 patients with CEP at several assessment points over 1 year.
  
  
  RESULTS
  FeNO level was positively correlated with peripheral eosinophil count (r = 0.341, P = 0.005) and percentage (r = 0.362, P = 0.003). The median (IQR) FeNO levels were 79 (41-88) and 35 (26-49) ppb in uncontrolled (13/74 measurements) and controlled (61/74 measurements) CEP, respectively (P = 0.010). The FeNO level of 66.0 ppb showed the largest area under the curve (0.835) for predicting exacerbation of CEP (sensitivity = 0.80, specificity = 0.84).
  
  
  CONCLUSIONS
  FeNO may be useful for monitoring eosinophilic parenchymal inflammation and determining the appropriate corticosteroid dose in CEP.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Park
authors.forename: Taehoon
authors.initials: T
authors.lastname: Lee
authors.forename: Hongyeul
authors.initials: H
authors.lastname: Lee
authors.forename: Yeon Joo
authors.initials: YJ
authors.lastname: Lee
authors.forename: Jong Sun
authors.initials: JS
authors.lastname: Park
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Cho
authors.forename: Ho Il
authors.initials: HI
authors.lastname: Yoon
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Respiratory Center, Seoul National University Bundang Hospital, 173-82 Gumi-Ro, Bundang-Gu, Seongnam 463-707, Republic of Korea. ctlee@snu.ac.kr.
authors.forename: Choon-Taek
authors.initials: CT
authors.lastname: Lee
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use*; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D002908:Chronic Disease; D015331:Cohort Studies; D018450:Disease Progression; D045853:Exhalation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D009569:Nitric Oxide / Q000032:analysis*; D011237:Predictive Value of Tests; D011657:Pulmonary Eosinophilia / Q000175:diagnosis* / Q000188:drug therapy*; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D009569:Nitric Oxide