Study objectives: It has been suggested that patients with noneosinophilic asthma (NEA) show increased numbers of sputum neutrophils and a lack of response to therapy with corticosteroids, which are features that are commonly related to COPD. The aim of our study was to test the hypothesis that airway inflammation in NEA patients is different from that seen in patients with eosinophilic asthma (EA) and is similar to COPD.
Design: Sputum cellular stress markers and neutrophilic and eosinophilic fluid-phase mediators were analyzed in asthma and COPD patients. NEA patients were identified based on a sputum eosinophil count of ≤ 2.2% of the total nonsquamous cell count, and were compared to EA and COPD patients.
Setting: University Hospital of Heraklion, Department of Thoracic Medicine.
Patients: A total of 37 atopic asthmatic patients and 25 patients with COPD.
Measurements: Sputum cell counts, cellular expression of heme oxygenase-1, inducible nitric oxide synthase, and nitrotyrosine, and sputum levels of eosinophilic cationic protein (ECP), myeloperoxidase (MPO), interleukin-8, and granulocyte macrophage colony-stimulating factor.
Results: A total of 17 asthmatic patients (46%) belonged to the NEA group and 20 patients (54%) to the EA group. Patients with NEA showed no difference in neutrophil counts, fluid-phase mediators, or cellular stress markers compared to patients with EA. Compared to COPD patients, NEA patients showed the following significant differences: lower total cell counts (p < 0.03); lower neutrophil counts (p < 0.01); lower nitrotyrosine positive cell counts (p < 0.003); lower ECP levels (p < 0.005); lower MPO levels (p < 0.000); higher lymphocyte counts (p < 0.01); and higher macrophage counts (p < 0.03).
Conclusions: Despite low eosinophil counts, airway inflammation in NEA patients may share common features with that in EA patients but is distinct from COPD. Larger studies are needed to investigate further the clinical and inflammatory characteristics of NEA before we are able to categorize asthma patients into those with or without eosinophilic inflammation.