Airway Inflammation and Cellular Stress in Noneosinophilic Atopic Asthma: Conclusion
However, the bronchodilator response tended to be smaller in NEA patients (p = 0.01). Accordingly, Green et al studied a large cohort of asthmatic patients and found no correlation between sputum eosinophil count and the FEV1 percent predicted. However, a weakly negative correlation was observed between the provocative concentration of methacholine causing a 20% fall in FEV1 and sputum eosinophil counts among atopic patients. Moreover, NEA patients with sputum neutrophilia showed irreversible airflow limitation after inhaled steroid treatment. Taken together, all of these findings and ours suggest that low sputum eosinophil counts might not predict increased asthma severity, but may indicate decreased bronchial hyperresponsiveness and poor response to treatment. so
Several investigators have addressed the important role of neutrophilic inflammation in NEA patients. Green et al identified in their cohort of asthmatic patients a subgroup with low eosinophil counts and sputum neutrophilia (23% of 259 asthmatic patients); however, not all NEA patients showed high neutrophil numbers. In another sputum study by Simpson et al, 28% of 93 asthma patients were noneosinophilic and neutrophilic. In our group of 37 asthmatic patients, only 2 patients (5%) showed high neutrophil counts (if the normal range for neutrophils is set to 65.3%, as in the study by Green et al). As expected, we did not find any difference in sputum neutrophil counts between subjects with sputum eosinophilia and those without. Similarly, Wenzel et al failed to find any connection between eosinophil and neutrophil numbers in endobronchial biopsy specimens from patients severe asthma. However, both our study and the study by Wenzel et al included a limited number of subjects, which perhaps did not allow the identification of an adequate number of neutrophilic asthmatic patients for the further differentiation of NEA into neutrophilic and nonneutrophilic. Moreover, we have evaluated only atopic asthmatic patients, while Green et al included equal numbers of atopic and nonatopic patients in their study. In fact, they found a connection between the subgroup of patients with neutrophilia and the absence of atopy. According to these results, which are in agreement with ours, neutrophilia might be a characteristic of nonatopic NEA.