title: Analysis of single-breath profiles of exhaled nitric oxide in children with allergy and asthma: guideline-derived plateau concentrations compared to results of automatic evaluation by two analyzers.
abstract: Current guidelines recommend the single-breath measurement of fractional concentration of exhaled nitric oxide (FE(NO)) at the expiratory flow rate of 50 mL/s as a gold standard. The time profile of exhaled FE(NO) consists of a washout phase followed by a plateau phase with a stable concentration. This study performed measurements of FE(NO) using a chemiluminescence analyzer Ecomedics CLD88sp and an electrochemical monitor NIOX MINO in 82 children and adolescents (44 males) from 4.9 to 18.7 years of age with corticosteroid-treated allergic rhinitis (N = 58) and/or asthma (N = 59). Duration of exhalation was 6 seconds for children less than 12 years of age and 10 seconds for older children. The first aim was to compare the evaluation of FE(NO)-time profiles from Ecomedics by its software in fixed intervals of 7 to 10 seconds (older children) and 2 to 4 seconds (younger children) since the start of exhalation (method A) with the guideline-based analysis of plateau concentrations at variable time intervals (method B). The second aim was to assess the between-analyzer agreement. In children over 12 years of age, the median ratio of FE(NO) concentrations of 1.00 (95% CI: 0.99-1.02) indicated an excellent agreement between the methods A and B. Compared with NIOX MINO, the Ecomedics results were higher by 11% (95% CI: 1-22) (method A) and 14% (95% CI: 4-26) (method B), respectively. In children less than 12 years of age, the FE(NO) concentrations obtained by the method B were 34% (95% CI: 21-48) higher and more reproducible (p < 0.02) compared to the method A. The Ecomedics results of the method A were 11% lower (95% CI: 2-20) than NIOX MINO concentrations while the method B gave 21% higher concentrations (95% CI: 9-35). We conclude that in children less than 12 years of age, the guideline-based analysis of FE(NO)-time profiles from Ecomedics at variable times obtains FE(NO) concentrations that are higher and more reproducible than those from the fixed interval of 2 to 4 seconds and higher than NIOX MINO concentrations obtained during a short exhalation (6 seconds). The Ecomedics FE(NO) concentrations of children more than 12 years of age calculated in the interval of 7 to 10 seconds represent plateau values and agree well with NIOX MINO results obtained during a standard 10-second exhalation.
authors.affiliation: Department of Pediatrics, Faculty of Medicine in Hradec Kralove, Charles University in Prague, Hradec Kralove, Czech Republic.
authors.forename: Jirina
authors.initials: J
authors.lastname: Chládková
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Havlínová
authors.forename: Tomás
authors.initials: T
authors.lastname: Chyba
authors.forename: Irena
authors.initials: I
authors.lastname: Krcmová
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Chládek
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001249:Asthma / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000032:analysis*; D017410:Practice Guidelines as Topic; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012130:Respiratory Hypersensitivity / Q000378:metabolism*; D013147:Spirometry; D055815:Young Adult
chemical_list: D009569:Nitric Oxide