Are exhaled nitric oxide measurements using the portable NIOX MINO repeatable?

BACKGROUND: Exhaled nitric oxide is a non-invasive marker of airway inflammation and a portable analyser, the NIOX MINO (Aerocrine AB, Solna, Sweden), is now available. This study aimed to assess the reproducibility of the NIOX MINO measurements across age, sex and lung function for both absolute and categorical exhaled nitric oxide values in two distinct groups of children and teenagers. METHODS: Paired exhaled nitric oxide readings were obtained from 494 teenagers, aged 16-18 years, enrolled in an unselected birth cohort and 65 young people, aged 6-17 years, with asthma enrolled in an interventional asthma management study. RESULTS: The birth cohort participants showed a high degree of variability between first and second exhaled nitric oxide readings (mean intra-participant difference 1.37 ppb, 95% limits of agreement -7.61 to 10.34 ppb), although there was very close agreement when values were categorised as low, normal, intermediate or high (kappa = 0.907, p < 0.001). Similar findings were seen in subgroup analyses by sex, lung function and asthma status. Similar findings were seen in the interventional study participants. CONCLUSIONS: The reproducibility of exhaled nitric oxide is poor for absolute values but acceptable when values are categorised as low, normal, intermediate or high in children and teenagers. One measurement is therefore sufficient when using categorical exhaled nitric oxide values to direct asthma management but a mean of at least two measurements is required for absolute values.

Exhaled nitric oxide monitoring does not reduce exacerbation frequency or inhaled corticosteroid dose in paediatric asthma: a randomised controlled trial.

INTRODUCTION: Inhaled corticosteroid therapy (ICS) for asthma is currently modified according to symptoms and lung function. Fractional exhaled nitric oxide (FENO) has been demonstrated to be a non-invasive marker of eosinophilic inflammation. Studies of FENO-driven asthma management show variable success. Objectives: This study aimed to evaluate whether monitoring FENO can improve outpatient management of children with moderate to severe asthma using a pragmatic design. METHODS: Children aged 6­17 years with moderate to severe asthma were recruited. Their asthma was stabilised before randomisation to FENO-driven therapy or to a standard management group where therapy was driven by conventional markers of asthma control. ICS or long-acting bronchodilator therapies were altered according to FENO levels in combination with reported symptoms in the FENO group. Participants were assessed 2 monthly for 12 months. ICS dose and exacerbation frequency change were compared between groups in an intention to treat analysis. RESULTS: Ninety children were randomised. No difference was found between the two groups in either change in corticosteroid dose or exacerbation frequency. Results were similar in a planned secondary analysis of atopic asthmatics. CONCLUSION: FENO-guided ICS titration does not appear to reduce corticosteroid usage or exacerbation frequency in paediatric outpatients with moderate to severe asthma. This may reflect limitations in FENO-driven management algorithms, as there are now concerns that FENO levels relate to atopy as much as they relate to asthma control.