Characteristics of Induced-Sputum Inflammatory Phenotypes in Adults with Asthma: Predictors of Bronchial Eosinophilia

Abstract

Purpose The objectives of this study were, for patients attending a specialist asthma clinic at a tertiary care hospital, to determine, from sputum induction (SI), proportions of bronchial inflammatory phenotypes, demographic, clinical and functional characteristics of each phenotype, and the most accessible non-invasive inflammatory marker that best discriminates between phenotypes. Patients and Methods Included were 96 patients with asthma, attending a specialist asthma clinic at a tertiary care hospital, who underwent testing as follows: SI, spirometry, fractional exhaled nitric oxide (FeNO), blood eosinophilia, total immunoglobulin E (IgE), and a skin prick test. Results SI phenotypes were 46.9% eosinophilic, 33.3% paucigranulocytic, 15.6% neutrophilic, and 4.2% mixed. No significantly different clinical or functional characteristics were observed between the phenotypes. A positive correlation was observed between SI eosinophilia and both emergency visits in the last 12 months (p = 0.041; r = 0.214) and FeNO values (p = 0.000; r = 0.368). Blood eosinophilia correlated with SI eosinophilia (p = 0.001; r = 0.362) and was the best predictor of bronchial eosinophilia, followed by FeNO, and total blood IgE (area under the receiver operating characteristic curve (AUC-ROC) 72%, 65%, and 53%, respectively), although precision was only fair. Conclusion In consultations for severe asthma, the most frequent phenotype was eosinophilic. Peripheral blood eosinophilia is a reliable marker for discriminating between different bronchial inflammatory phenotypes, is useful in enabling doctors to select a suitable biologic treatment and so prevent asthma exacerbation, and is a better predictor of bronchial eosinophilia than FeNO and IgE values.

Involvement of Transforming Growth Factor-β-Associated Kinase 1 in Fixed Airway Obstruction in Asthmatic Patients with Longer Disease Duration Independent on Airway Eosinophilia

“…[49][50][51] Asthmatics treated with moderate ICS in FAO group had similar FeNO levels and sputum eosinophil percent to those of unselected asthmatics and those of well-controlled asthmatics, [52][53][54] whereas both biomarkers were lower than those of uncontrolled asthmatics. 55,56 We did not find the association between both biomarkers and FAO status and the relationship of eosinophil activation with FAO status as demonstrated by others. 57 However, our results confirmed earlier studies that aging was associated with FAO and lower FeNO concentrations as demonstrated by the evidence that asthmatics with FAO were significantly older and tended to have lower FeNO levels, albeit statistically insignificant, than asthmatics with nFAO.…”

Asthma Inflammatory Phenotypes: How Can We Distinguish Them?

“…There was an almost equal distribution of EA (n = 25) and MGA (n = 24), while 19 subjects had PGA and 12 subjects had NA in the whole cohort. Other studies have also found EA to be the most prevalent phenotype, presented in 41%, 40%, and 46.9% of patients, respectively, but the distribution of the other three phenotypes was varying [9,30,31]. The predominance of the PGA phenotype was seen among 176 patients with asthma in China, in 42.6% [32].…”

“…We did not confirm the correlation between the number of eosinophils in blood and the % of eosinophils in sputum among patients with EA (ρ = −0.03, p = 0.863). The correlation between serum and sputum eosinophilia is seen in many studies [31,33,34]. Schleich et al have shown this connection in more than 500 asthmatics, and they have set the cut-off value of 220/µL of blood eosinophils to identify ≥3% eosinophils in sputum [35].…”

“…The differences in predominant phenotype may be explained by the diversity of cohorts. In other cross-sectional studies, like ours, the patients were also evaluated for maintenance therapy that could affect the "initial" phenotype, but a more severe asthma population was included [30][31][32].…”