Background Little is known regarding mechanistic and phenotypic variations between cough variant asthma (CVA), presenting having a chronic cough as the sole sign that responds to bronchodilators, and classic asthma with wheezing during methacholine inhalation. less reactive to inhaled methacholine and wheezed less regularly but coughed more frequently during methacholine-induced bronchoconstriction than did patients with classic asthma. Multivariate analysis exposed that airway Sema3f hypersensitivity and lower baseline FEV1/FVC were associated with the appearance of wheezes, whereas a analysis of CVA was associated with coughing. Summary You will find mechanistic and phenotypic variations between CVA and classic asthma during methacholine inhalation. Frequent coughing during bronchoconstriction may be a distinctive feature of CVA. Background Individuals with cough variant asthma (CVA) present having a chronic cough as the sole sign that responds to bronchodilator treatment and show airway hyperresponsiveness (AHR). CVA, probably one of the most common causes of chronic cough [1-4], is considered a precursor [5-9] and a variant form of classic asthma with standard symptoms of wheezing and dyspnea [5]. A number of studies have examined mechanistic variations between CVA and classic asthma. Airway level of sensitivity, a component of airway responsiveness that is defined as the inflection point where respiratory resistance (Rrs) starts to increase, did not differ between individuals with CVA and those with classic asthma in a few small studies [10,11]. In contrast, airway reactivity, another component of airway responsiveness indicated as the slope of the dose-response curve, is usually attenuated in children with CVA as compared with those with classic asthma [12]. In adults with CVA, however, no study offers separately examined airway level of sensitivity and reactivity in a large number of individuals. Methacholine, a non-specific cholinergic stimulant, induces bronchoconstriction without exacerbating airway swelling. Apart from an analysis of mechanistic elements, analyses of phenotypes, such as the appearance of cough and wheezes during methacholine-induced bronchoconstriction, may provide clues to understanding the unique features of CVA. To our knowledge, however, such an approach has not been attempted thus far. In one study in asthmatic children, detection of wheezes during methacholine inhalation depended on the degree of airway narrowing, while factors related to coughing during methacholine inhalation were not specified [13]. In this study, we initially examined airway level of sensitivity and reactivity to methacholine in adults with CVA and in those with classic asthma, using a continuous inhalation method that can Toosendanin separately evaluate these two parts [12,14]. Our major concern was the presence or absence of cough and wheezes during methacholine-induced bronchoconstriction. Factors associated with the appearance of cough and wheezes were then analyzed. Methods Study subjects and design We cross-sectionally analyzed adults with classic asthma (n = 58) or with CVA (55) who offered in the outpatient medical center of Kyoto University Hospital from 04 1993 to Toosendanin September 2001. Classic asthma was diagnosed according to the American Thoracic Toosendanin Society criteria [15]: the symptoms of episodic wheezing and dyspnea within the previous 12 months that responds to bronchodilators, and AHR to methacholine inhalation. CVA was diagnosed according to the following criteria [5,10]: an isolated chronic cough without wheezing or dyspnea that experienced persisted for more than 8 weeks, AHR to methacholine, and symptomatic improvement of coughing in response to inhaled beta-2 agonists, sustained-release theophylline, or both. Wheezing or rhonchi were not audible on chest auscultation, even with forced expiration. No patient experienced a past history of asthma or experienced an upper respiratory tract infection within the past 8 weeks. No additional apparent causes of chronic cough, such as gastroesophageal reflux, chronic sinusitis, or medication with angiotensin-converting enzyme inhibitors, Toosendanin were present. Individuals with CVA experienced normal chest radiographs and were steroid-na?ve, much like those with classic asthma. The ethics committee of our institution authorized the study protocol, and written knowledgeable consent was from each participant. Pulmonary function test and methacholine challenge test Prebronchodilator FEV1 was tested.