Background: The number of admissions to immunology and allergy clinics with chronic cough categorized as corticosteroid-responsive eosinophilic disorders are increasing. We aimed in this study to find the prevalence of Non-asthmatic eosinophilic bronchitis (NAEB), Cough variant asthma (CVA), Atopic cough (AC) and β2 agonist response among NAEB.
Material and methods: Cross-sectional study was performed in an immunology and allergy department in patients suffering from chronic cough persisting for longer than eight weeks. Clinical history, physical examination, skin allergy tests, spirometry (lung function and reversibility) methacholine airway responsiveness (BPT), total IgE and eosinophil count in blood and bronchoalveolar lavage (BAL) were assessed. After bronchoscopic procedure they received bronchodilator treatment and then inhaled corticosteroid (ICS). According to the Japanese Cough Research Society, they are classified as AC, CVA, NAEB and idiopatic cough. If BAL procedure could not be performed and there was absence of AHR but there was positive response to bronchodilator treatment, we classified it as Non-hyperresponsive β2 agonist responsive cough (NHBRC).
Results: In our study the common cause of 41 corticosteroid-responsive chronic cough is CVA, (41.4%) followed by NAEB (26.8%), NHBRC (19.5%), AC (9.7%) and idiopatic (2.4%) respectively. 72.7% of NAEB patients have good response to β2 agonist treatment. When we compare percentage of eosinophils in BAL fluid; NAEB has significantly higher than in CVA (p=0.005). In NAEB, after reversibility test and BPT, even if PEF% is not significantly changed (p>0.05), FEF25-75% is significantly changed (p<0.05). On the other hand compared with NAEB, FEF25-75% is significantly increased in NHBRC after reversibility test and significantly decreased in CVA after BPT.
Conclusions: Observing β2 agonist response is a simple procedure most likely to differentiate NAEB and CVA from AC. FEF25-75 is seem to be determinative for AHR in CVA, effectiveness of FEF25-75 rather than PEF in NAEB is considered so that NAEB may develop to CVA with time.
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