PURPOSE OF THE STUDY.
To evaluate the relationship between exhaled nitric oxide fraction (FeNO) and increased airway responsiveness, and to clarify whether there are any associations between these measures and risk factors for respiratory morbidity in infants with recurrent lower respiratory tract symptoms.
Studied subjects were 444 children aged <3years with recurrent lower respiratory tract symptoms including wheeze, dry or productive cough, and/or shortness of breath.
Subjects were assessed for FeNO, lung function tests, and the dosimetric methacholine challenge test. Blood was collected for the analysis of peripheral blood eosinophil count. Clinical data were collected by interviewing the parents and by reviewing the medical records of the children.
A total of 136 full-term, steroid-free, infection-free infants, median ages of 16.4 months (range 4.0–26.7 months) were enrolled. The median level of FeNO was 19.3 ppb. Elevated FeNO (≥27 ppb) was associated with maternal history of asthma (adjusted odds ratio, 3.2; P = .012) and increased airway responsiveness (adjusted odds ratio, 4.1; P = .012). However, atopy, blood eosinophilia, lung function, age, height, gender, paternal history of asthma or allergy, parentally reported respiratory symptoms, physician-confirmed wheeze, and environmental exposures were not associated with elevated FeNO.
Among infants with recurrent lower respiratory tract symptoms, elevated FeNO was significantly associated with a maternal history of asthma, and with increased airway responsiveness to methacholine.
The results of the present cross sectional study provides further evidence that increased airway responsiveness and maternal, not paternal, history of asthma are significant factors determining FeNO levels in infants with recurrent respiratory symptoms. However, there was no mention of severity level classification of respiratory symptoms. Therefore, it was not possible to explore the influence of disease severity. That no relationship between FeNO levels and peripheral blood eosinophilia was found suggests that elevated FeNO levels may reflect inflammatory factors other than eosinophilic inflammation identified in blood; sputum eosinophils, although much less practical to obtain, particularly in infants, may be worth investigating. This study possibly has an influence in clinical practice for infants with recurrent lower respiratory tract symptoms. Future studies are needed in larger cohorts to determine whether FeNO can be a noninvasive predictor or biomarker for monitoring respiratory disease, such as asthma or wheezing, in infants.
- Copyright © 2013 by the American Academy of Pediatrics