title: Variability of FeNO in healthy subjects at 2240 meters above sea level.
abstract: Fraction of exhaled nitric oxide (FeNO) is a marker of eosinophilic airway inflammation. Altitude above sea level can affect measurements of this index, but there is only limited information regarding the diurnal variation (ante meridiem vs. post meridiem) and reproducibility of FeNO on consecutive days at moderate altitudes. To evaluate the diurnal variability of FeNO and assess its reproducibility over five consecutive days in healthy individuals living at 2240 m, and to compare the FeNO readings taken with two different analyzers. Healthy non-smoking adults were measured using NIOX MINO(®) or NOA 280i(®) devices. One group (n = 10) had readings taken morning and afternoon for five consecutive days with the NIOX MINO(®) equipment; while the second group (n = 17) was measured on only one morning but by both the electrochemical analyzer (NIOX MINO(®)) and the chemiluminescence method (NOA 280i(®)). The study group consisted of 27 subjects aged 28.7 ± 6 years. Morning and afternoon FeNO measurements were 15.2 ± 7.5 ppb and 15.2 ± 7.9 ppb (p = 0.9), respectively. The coefficient of variation (CV) of these measurements (a.m. vs. p.m.) was 10.7 %, and the coefficient of repeatability (CR), 4.2 ppb. The concordance correlation coefficient (CCC) between the two measures (morning vs. afternoon) was 0.91. The CV and CR of the five morning readings were 15.4 % and 4.3 ppb, respectively; while those of the five afternoon measures were 13.6 % and 3.5 ppb, respectively. The CCC between the NIOX MINO(®) equipment and the NOA-280i(®) device was 0.8, with 95 % limits of agreement of -8.35 to 0.29 ppb. In adults living at 2240 m above sea level, FeNO measurements show minimal diurnal variation, and readings are reproducible (<15 %) over a period of at least five consecutive days; however, the FeNO measurements obtained with the NIOX MINO(®) and NOA 280i(®) devices are not interchangeable due to the wide limits of agreement recorded.
authors.affiliation: Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Calzada de Tlalpan 4502, Colonia Sección XVI, Tlalpan, C.P. 14080, Mexico City, Distrito Federal, Mexico.
authors.forename: Laura
authors.initials: L
authors.lastname: Gochicoa-Rangel
authors.affiliation: Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Calzada de Tlalpan 4502, Colonia Sección XVI, Tlalpan, C.P. 14080, Mexico City, Distrito Federal, Mexico.
authors.forename: Fermín
authors.initials: F
authors.lastname: Rojas-Cisneros
authors.affiliation: Clínica de Asma, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Mexico City, Mexico.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Miguel-Reyes
authors.affiliation: Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Calzada de Tlalpan 4502, Colonia Sección XVI, Tlalpan, C.P. 14080, Mexico City, Distrito Federal, Mexico.
authors.forename: Selene
authors.initials: S
authors.lastname: Guerrero-Zúñiga
authors.affiliation: Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Calzada de Tlalpan 4502, Colonia Sección XVI, Tlalpan, C.P. 14080, Mexico City, Distrito Federal, Mexico.
authors.forename: Uri
authors.initials: U
authors.lastname: Mora-Romero
authors.affiliation: Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Calzada de Tlalpan 4502, Colonia Sección XVI, Tlalpan, C.P. 14080, Mexico City, Distrito Federal, Mexico.
authors.forename: Ana Karen
authors.initials: AK
authors.lastname: Maldonado-Mortera
authors.affiliation: Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas", Calzada de Tlalpan 4502, Colonia Sección XVI, Tlalpan, C.P. 14080, Mexico City, Distrito Federal, Mexico. luistorreb@gmail.com.
authors.forename: Luis
authors.initials: L
authors.lastname: Torre-Bouscoulet
mesh_terms: D000328:Adult; D000531:Altitude; D001249:Asthma / Q000378:metabolism; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D004802:Eosinophilia / Q000378:metabolism; D045853:Exhalation; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D009569:Nitric Oxide
keywords: Chemiluminescence; Circadian variation; Cut-off points; Electrochemical analyzer; Exhaled nitric oxide