The Effect Of Inhaled Corticosteroid On Inflammatory Mediators In Induced Sputum And Airway Hyperresponsiveness In Cough Variant Asthma

BackgroundCough variant asthma (CVA) is an occult form of classic asthma that solely presents with chronic cough (lasting for more than8weeks) and responds to bronchodilator treatment. Several studies have suggested that airway inflammation and bronchial hyperresponsiveness (BHR) are the fundamental pathophysiological characters of cough variant asthma, just the same as classic asthma. Inhaled corticosteroid (ICS) is considered the first-line therapeutic approach to CVA which is similar to classic asthma. Nevertheless, the trend of improvement in BHR and airway inflammation including regulatory markers in cough variant asthma responding to ICS treatment, particularly as compared with mild classic asthma, has not yet been elucidated. The purpose of this study was to compare the changes in airway inflammation and bronchial hyperresponsiveneess between CVA and classic asthma and stepwise estimated the effect of ICS treatment on cough variant asthma.MethodWe collected and screened28patients with cough variant asthma (CVA group) and23patients with typical asthma (asthma group),22healthy subjects served as the control group. All patients were required to performed spirometry, bronchial provocation test and examination of induced sputum. After participating in the study, all patients were treated with budesonide(400ug/day) and the follow-up period lasted for twelve months. The value of PD20-FEV1was evaluated before and3、6、9、12months after the treatment. The level of IL-5and IL-10in induced sputum before and3、6、9、12months after the treatment were measured using sandwith enzyme-linked immunosorbent assay(ELISA) and the percentage of eosinophil in induced sputum was accounted with Wright and Gimsa stain.ResultsPD20-FEV1significantly increased in CVA patients after taking ICS for3months.12-months’ ICS treatment can improve airway hyperresponsiveness up to the mildest degree. Accordingly, classic asthma has delayed change in AHR. ICS treatment can also considerably ameliorate the level of inflammatory mediators both in cough variant asthma and classic asthma. CVA has advanced improvement in the concentrations of sputum IL-5and IL-10as well as the percentage of eosinophils comparing with classic asthma. The levels of inflammatory mediators in induced sputum in cough variant asthma all differ from those in asthma due to the apparent difference of each detected marker’s value during the follow-up period.ConclusionCough variant asthma has better improvement of airway inflammation and airway hyperresponsiveness (AHR) than classic asthma with respect to inhaled corticosteroid(ICS). Short-term ICS significantly reduces AHR while complete control of airway inflammation yet need longer time of ICS treatment.