Exhaled nitric oxide and childhood asthma
Article Outline
To the Editor:
Sivan et al investigated the use of exhaled nitric oxide (FeNO) in the diagnosis of asthma in school-age children.1 They found a remarkable high diagnostic yield of FeNO and concluded that the test should be considered in the evaluation of children suspected of having asthma.
Earlier studies on the matter have led to inconclusive results.2, 3, 4 Unfortunately, neither Sivan et al nor other authors evaluated the additional value of FeNO compared with readily available information, such as a simple patient history.1, 2, 3, 4 The authors did compare the diagnostic yield of FeNO with that of sputum eosinophils.1 It is not surprising that a combination of these 2 measurements did not improve the area under the receiver operating characteristic curve for the diagnosis of asthma, because both were highly correlated.
The clinically relevant question remains: What is the added value of FeNO compared with available information in clinical practice? We would be interested to see this analysis performed on the study material of Sivan et al. Besides a clinical history, it would be useful to take specific immunoglobulin E into account. It has been suggested that a large part of the association between FeNO and asthma may be explained by the correlation between FeNO and atopy.5
Second, we want to express our concern about the exclusion criteria. Although not explicitly stated, it seems from the footnote of Table II that more than one-third of the children with asthma (n = 37; Table I) were excluded from analysis because of steroid use before the study inclusion.1 Information on earlier steroid use in children without asthma is not provided. Exclusion of steroid users selectively from the asthma group and not from the non-asthma group leads to biased results, with overestimation of the diagnostic yield of FeNO.
References
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- . Exhaled nitric oxide rather than lung function distinguishes preschool children with probable asthma. Thorax. 2003;58:494–499
- . Exhaled nitric oxide as a screening tool for asthma in school children. Respir Med. 2006;100:167–173
- . The relationship of exhaled nitric oxide to airway inflammation and responsiveness in children. J Asthma. 2005;42:291–295
- . The value of FeNO measurement in asthma management: the motion against FeNO to help manage childhood asthma—reality bites. Paediatr Respir Rev. 2008;9:122–126
PII: S0022-3476(09)01090-7
doi:10.1016/j.jpeds.2009.11.005
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