Abstract
BackgroundThere is a need to identify the asthma inflammatory phenotypes of patients to facilitate personalized asthma treatment. Sputum induction is time-consuming and requires expert clinical technique. This study aimed to assess the distribution and characteristics of asthma inflammatory phenotypes in Jilin Province, China; it also aimed to identify an easier method for characterization of an asthma phenotype, rather than sputum cellular analysis.MethodsIn this study, 232 asthma patients underwent sputum induction following clinical assessment and blood collection. Inflammatory cell counts in sputum were used to classify asthma inflammatory phenotypes. Receiver operating characteristic curve and Spearman correlation coefficient analyses were used to identify correlations between clinical parameters.ResultsAmong the included patients, there had 52.1% paucigranulocytic, 38.4% eosinophilic, 4.3% neutrophilic, and 5.2% mixed granulocytic asthma phenotypes, respectively. In total, 129 (55.6%) patients had asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO); these patients had higher proportion of smokers, higher sputum neutrophil count, worse lung function, and worse asthma control, compared with patients who had asthma alone (p < 0.05). Sputum eosinophil/neutrophil counts were positively correlated with blood eosinophil/neutrophil counts (p < 0.01). To identify the presence of sputum eosinophil proportion ≥ 3%, optimal cut-off values for blood eosinophil count and fractional exhaled nitric oxide (FeNO) were 0.2 × 109/L and 30.25 ppd (area under the curve (AUC) = 0.744; AUC = 0.653, p < 0.001). AUCs did not significantly differ between FeNO and blood eosinophil count (p = 0.162), but both exhibited poor specificity (57% and 49%, respectively). To identify the presence of sputum neutrophil proportion ≥ 61%, the optimal cut-off value for blood neutrophil proportion was 69.3% (AUC = 0.691, p = 0.0003); however, this exhibited poor sensitivity (50%).ConclusionsPaucigranulocytic asthma was the most common phenotype, followed by eosinophilic asthma. Higher proportion of smokers, poor patient compliance, insufficient treatment, and poor asthma control may have been the main causes of high ACO proportion among patients in this study. Blood eosinophil/neutrophil counts exhibited poor specificity and sensitivity for prediction of airway eosinophilic/neutrophilic inflammation.
Highlights
There is a need to identify the asthma inflammatory phenotypes of patients to facilitate personalized asthma treatment
When all variables were entered into the model, we found that blood eosinophil proportion and Asthma Control Test Questionnaire (ACT) score were identified as independent predictors of sputum eosinophil proportion ≥ 3% (Table 5)
Simpson et al reported that macrophage phagocytosis was severely impaired in patients with non-eosinophilic asthma [30]; we observed that sputum macrophages were significantly reduced in patients with neutrophilic asthma (NA), which may explain the persistent elevation of airway neutrophil counts in these patients
Summary
There is a need to identify the asthma inflammatory phenotypes of patients to facilitate personalized asthma treatment. Sputum induction is time-consuming and requires expert clinical technique. This study aimed to assess the distribution and characteristics of asthma inflammatory phenotypes in Jilin Province, China; it aimed to identify an easier method for characterization of an asthma phenotype, rather than sputum cellular analysis. Airway inflammation in some patients with asthma exhibits neutrophil dominance, non-Th2-mediated airway inflammation, and poor response to current therapies [4, 5]. Sputum induction for inflammatory cell analysis is the currently accepted method for identifying asthma inflammatory phenotype [7]. Sputum induction requires expert clinical technique and good patient cooperation; the process is time-consuming. Some studies have proposed the possibility of fractional exhaled nitric oxide (FeNO) levels and whole blood eosinophil counts for prediction of airway eosinophilic inflammation [8, 9], but there remains insufficient evidence to support the reliability of this method, especially in China
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