Nasal lavage, blood or sputum: Which is best for phenotyping asthma?

Abstract

Background and objective: Determination of asthma phenotypes, particularly inflammatory phenotypes, helps guide treatment and management of this heterogeneous disease. Induced sputum cytology has been the gold standard for determination of inflammatory phenotypes, but sputum induction is fairly invasive and technically challenging. Blood and nasal lavage cytology have been suggested as substitutes, but have not been fully verified. The aim of this study is to determine the accuracy of blood and nasal lavage cytometry as indicators of inflammatory phenotypes in asthma. Methods: Clinical evaluation, Asthma Control Questionnaire (ACQ) and spirometry were performed for 121 adult asthma patients, and blood, nasal lavage and induced sputum samples were taken. Eosinophils and neutrophils were counted in three samples from each subject. Inflammatory phenotypes (eosinophilic, neutrophilic, mixed and paucicellular) and cells counts were analysed using Venn diagram and receiver operating characteristic (ROC) curve, respectively. Results: ACQ score, spirometry and bronchodilator response did not differ among subjects with different inflammatory phenotypes. Inflammatory phenotypes defined by nasal lavage cytometry were in better concordance than those defined by blood cell counts with phenotypes determined by sputum cytology, and were significantly correlated with sputum phenotypes. For eosinophilia, nasal lavage cytology showed better accuracy than blood cytology (area under the curve (AUC): 0.89 vs 0.65). For all phenotypes, sensitivity and positive and negative predictive power were higher for nasal lavage cytometry than for blood. Blood cell counts gave a high level of false positives for all inflammatory phenotypes. Conclusion: We recommend nasal lavage cytology over blood cell count as a substitute for sputum cytology to identify inflammatory phenotypes in asthma.

Alternatives to induced sputum for identifying inflammatory subtypes of asthma

“…is remarkably similar to a number of other large cohorts and the largest study of more than 500 adults showed blood eosinophils to be independent predictor of sputum eosinophilia . Sensitivity of blood eosinophils to predict sputum eosinophilia seems to vary significantly, with the study of De Farias et al . observing a much lower sensitivity around half of that reported in the other studies.…”

“…By comparison, blood eosinophils had a lower specificity (72%) for identifying eosinophilic asthma and therefore a lower area under the curve following receiver operator curve (ROC) analysis. The specificity of blood eosinophils reported by De Farias et al . is remarkably similar to a number of other large cohorts and the largest study of more than 500 adults showed blood eosinophils to be independent predictor of sputum eosinophilia .…”

“…Alternately, in patients with severe and often refractory asthma, the identification of eosinophilic inflammation and use of add‐on therapies such as mepolizumab may reduce the incidence of severe exacerbations and support a reduction in the requirement for oral corticosteroids . De Farias et al . ask the question which sample type is best for phenotyping asthma?…”

“…observing a much lower sensitivity around half of that reported in the other studies. Differences in peripheral eosinophil count cut‐off values of blood eosinophilia (>220 cells/mm 3 , used by De Farias et al …”

Year in review 2017: Chronic obstructive pulmonary disease and asthma

“…Blood cell count is often used as a substitute for sputum cytology to identify inflammatory phenotypes in asthma. de Farias et al . reported that nasal lavage cytometry showed better accuracy than blood cell count for characterizing asthma inflammation and recommended the use of nasal lavage cytology as an easy and accurate substitute for induced sputum cytology.…”