Fraction of exhaled nitric oxide and asthma predictive index in infants less than two years-old

Abstract

Introduction: The fraction of exhaled nitric oxide (FE(NO)) is considered as an indirect marker of eosinophilic inflammation of the airway. In collaborating children the usual method is by a single breath. The impossibility of performing this in non-collaborating children has led to the development of the online and offline tidal breathing technique. The objective of the study has been to analyse the relationship between the multiple breaths online FE(NO) and the asthma predictive index (API) in children less than 2 years-old.

Material and methods: An observational and cross-sectional study on a consecutive sample of boys and girls between 2 months and 2 years of age, over a period of 4 months. The post-prandial multiple breaths online FE(NO) and flow spirometry between 40 and 60 ml/s, using a stationary chemiluminescence analyser (CLD 88 sp). The quantitative variables were: age, weight, IgE, eosinophilia, FE(NO), flow spirometry. The qualitative variables were: gender, atopic dermatitis, allergic rhinitis, food and medical allergies, family history of asthma and atopy, diagnosis and treatment. The relationship between API and FE(NO) was analysed using the exact Fisher and Student t tests and the level of agreement between API and FE(NO) using Cohen's Kappa. The relationship between eosinophilia, IgE, atopic dermatitis and FE(NO) was also studied (exact Fisher and Student t tests).

Results: The cohort consisted of 38 patients. The determinations were successfully carried out on 32 (84.21) of the cases. The mean age was 10.9±5.06 months. The cases with a positive API had significantly higher FE(NO) values than those with a negative API, with a level of agreement between API and FE(NO) of 0.71.

Conclusions: There is a significant relationship and a good level of agreement between the online tidal breathing FE(NO) and the API.