title: Stability of sealed-bag samples for off-line measurement of fractional exhaled nitric oxide.
abstract: BACKGROUND
  Fractional exhaled nitric oxide (FeNO) measurement is an index of airway eosinophilic inflammation and is primarily employed to diagnose bronchial asthma and assess airway inflammation. It can be measured with on- and off-line methods. In the latter, sample storage is possible; this is useful in Japan, because the number of facilities in which this instrument has been installed is limited.
  
  
  OBJECTIVE
  We investigated the maximum period in which the samples continued to show stable values, as well as the influences of the storage environment.
  
  
  METHODS
  Exhaled air samples were collected from 19 bronchial asthma patients (male/female: 8/11; mean age: 54.9 ± 15.6 years), and divided into 2 groups: a group with an FeNO level of less than 30 ppb and that with a level of 30 ppb or more. They were stored at 4 and 25°C to examine serial changes.
  
  
  RESULTS
  The off-line-measured FeNO value was 33.7 ± 17.1 ppb, significantly lower than the on-line measured value (71.4 ± 47.7 ppb) (P < .01). In a group with an FeNO level of less than 30 ppb, temperature had no influence. However, in the other group, the period was prolonged to 72 hours when the samples were stored at 4°C. The samples were stable at 4°C for 24 hours, regardless of the initial measurements.
  
  
  CONCLUSIONS
  The duration of sample storage can be prolonged at 4°C. The standard FeNO measurement method is the on-line method, but the alternative use of the off-line method may contribute to the diagnosis and treatment of the patients.
authors.affiliation: Department of Respiratory Medicine, Kawasaki Medical School, Japan. shimizu@med.kawasaki-m.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shimizu
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Obase
authors.forename: Masaki
authors.initials: M
authors.lastname: Ikeda
authors.forename: Koji
authors.initials: K
authors.lastname: Kurose
authors.forename: Masaaki
authors.initials: M
authors.lastname: Abe
authors.forename: Keiji
authors.initials: K
authors.lastname: Mouri
authors.forename: Shigeki
authors.initials: S
authors.lastname: Katoh
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Miyashita
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kobashi
authors.forename: Mikio
authors.initials: M
authors.lastname: Oka
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis / Q000378:metabolism; D001944:Breath Tests / Q000379:methods; D003080:Cold Temperature; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis* / Q000378:metabolism; D013048:Specimen Handling / Q000379:methods*
chemical_list: D009569:Nitric Oxide