| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Senior Lecturer in Child Health, University of Aberdeen, Royal Aberdeen Children's Hospital, Aberdeen, UK
To the Editors:
The paper by Brussee et al. 1 describes the first large survey of the fraction of exhaled nitric oxide (FeNO) in a young population. The authors should be congratulated for undertaking such a study in an age range where great patience and persistence are required to obtain data.
Brussee et al. 1 reported only a marginal increase in FeNO among atopic and asthmatic children compared with the nonatopic nonasthmatic children studied. One explanation for the large overlap in the distribution of FeNO in children with and without asthma or atopy could be that, at this age, the difference is simply smaller than in older children. There are three methodological issues that may have reduced the ability of the study to detect differences in FeNO between groups, and I would be grateful if the authors would clarify these issues.
First, in the study, the mean FeNO from two exhaled breath samples was reported, unless the individual values varied by >10 ppb. Current guidelines recommend that paired on-line FeNO values should be within 5% of each other 2, but these criteria may be too stringent in young children whose FeNO values are low relative to older children. How did the authors determine the criteria for their recent study 1? As the difference between paired values increases, the criteria used in this study will result in FeNO reflecting allergic airway inflammation less accurately; for example, paired values of 4 ppb ("low") and 12 ppb ("high") would be reported as 8 ppb ("average"), but which, if either, value was "correct"? If stricter criteria were applied (for example, only considering paired measurements within 5 ppb of each other), were FeNO values more discriminating between atopic and nonatopic children, even though fewer data points are analysed?
Secondly, This group has previously reported that paired measurements using this technique were within the limits of agreement 3. Did the authors also find good reproducibility between the paired FeNO values in the study of 4-yr-old children 1? Finally, the authors have previously reported 2 that ambient nitric oxide of <20 ppb influenced the FeNO values using the apparatus from the recent study 1. I note that in the recent study, children inhaled through a charcoal nitric oxide filter, and that measurements were not taken on days when ambient nitric oxide exceeded 20 ppb. The authors report that, when analyses were limited to children where ambient nitric oxide levels were <10 ppb at the time of testing, similar results to the whole population were obtained 1.
Thus, ambient nitric oxide does not appear to have substantially influenced the relationship between the fraction of exhaled nitric oxide and asthma/atopy, but I would appreciate it if the authors could clarify whether ambient nitric oxide influenced the fraction of exhaled nitric oxide.
REFERENCES
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
