The aim of the study is to assess the prevalence of bronchial hyperresponsiveness (BHR) in non-smoking adults with chronic cough and the prevalence of BHR in patients with upper airway cough syndrome (UACS) and gastroesophageal reflux disease (GERD), to evaluate the relationship between BHR and cough reflex sensitivity, to assess the diagnostic accuracy of methacholine challenge test (MCT) in cough variant asthma (CVA) with special regard to its discriminating cut off value between CVA and other causes of chronic cough, particularly GERD, to estimate prognostic value of BHR, fractional exhaled nitric oxide (FeNO) and induced sputum eosinophil count in predicting response to asthma treatment. Patients diagnosed with a chronic cough will undergo the standard diagnostic work-up recommended by experts for patients with a chronic cough, including methacholine challenge test (MCT) and an at least 4-week period of causal treatment. Patients with BHR in MCT will be treated with - in first step B2-agonist and inhaled corticosteroid (ICS) for at least 4 weeks, if improvement is not significant in next steps with leukotriene receptor antagonist (LTRA) or systemic corticosteroid. A good treatment response, evaluated by visual analogue scale (VAS), Leicester Cough Questionnaire (LCQ) and cough challenge will confirm the diagnosis of the disease. A statistical analysis will consist of the frequency of BHR in a chronic cough, correlation between the results of MCT and cough reflex sensitivity in capsaicin inhalation test and cut-off point for MCT to discriminate asthma from other causes of a chronic cough.
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The decrease of a cough after cough variant asthma therapy measured by Leicester Cough Questionnaire (LCQ).
Timeframe: at least 4 weeks of treatment
The decrease of a cough after cough variant asthma therapy measured by Visual Analogue Scale (VAS).
Timeframe: at least 4 weeks of treatment
The decrease of a cough after cough variant asthma therapy measured by the cough challenge.
Timeframe: at least 4 weeks of treatment