Clinical and inflammatory features of asthma with dissociation between fractional exhaled nitric oxide and eosinophils in induced sputum

Abstract

Background: Measurement of the fractional exhaled nitric oxide (FeNO) and eosinophils in induced sputum are noninvasive markers for assessing airway inflammation in asthma. The clinical usefulness of the correlation between raised FeNO and sputum eosinophilia is controversial. We aimed to examine dissociation between FeNO and sputum eosinophils in a clinical series of asthma patients and to determine whether dissociation between these noninvasive markers was associated with clinical and inflammatory differences in these patients. Methods and findings: A total of 110 patients with asthma were included in a cross-sectional study. All of them were on maintenance treatment for asthma. All patients underwent the following on the same day: FeNO, induced sputum, spirometry, serum total IgE levels and skin prick test. The level of asthma control was determined by the Asthma control Test Questionnaire. In 46 (41.8%) patients, a discrepancy between FeNO and sputum eosinophil count was observed, of those, 34 (73.9%) had a FeNO <50 ppb and high eosinophil count, and were characterized by having a predominance of nonallergic asthma with bronchial eosinophilic inflammatory phenotype. Also, 12 (26.1%) patients had FeNO ≥50 ppb and sputum eosinophilia within the normal reference values, and were characterized by having a predominance of atopy with a paucigranulocytic inflammatory phenotype. Conclusions: A high percentage of patients with dissociation between results of FeNO and sputum eosinophils was observed. These patients showed differential clinical and inflammatory features.

• Asthma
• asthma phenotype
• eosinophils
• exhaled nitric oxide
• induced sputum

Acknowledgements

The authors thank Marta Pulido, MD, for editing the manuscript and editorial assistance.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

This paper is part of the doctoral thesis of A.C.

Supplementary material available online Supplementary Table 1