Validation of a hand-held exhaled nitric oxide analyzer for use in children

Measurements of exhaled nitric oxide (FE(NO)) may be useful in the diagnosis and management of asthma in children. A new hand-held device (MINO, Aerocrine) for measuring FE(NO) has been marketed but has not been validated in a pediatric population. The objective is to validate the MINO against the NIOX analyzer. This was a randomized cross-over study where FE(NO) was measured in a single assessment using the MINO and NIOX. Children were recruited from a respiratory clinic and had six attempts to provide a FE(NO) measurement with each analyzer. Fifty-five children were enrolled, 33 boys, median age 9 years. A mean FE(NO) value was obtained in 39 children with MINO and 44 with NIOX. Paired mean FE(NO) values were obtained in 34 children and the values were higher for the NIOX (mean difference 3.9 ppb limits of agreement -1.1, 8.9). The differences between analyzers became greater at higher FE(NO) values. The first FE(NO) value using the MINO was 24 ppb and the mean of all FE(NO) values using the MINO was 27 ppb (difference not significant). Exhaled NO values were comparable between the two analyzers although there was greater consistency at lower values. The findings of the study do not contradict the manufacturer's recommendation that only one FE(NO) value is required with the MINO, however, we suggest that the mean of at least two values should be reported in children.