Prevalence of Cough Variant Asthma in Patients with Chronic Cough Attending Vali-e Asr Hospital of Zanjan, Iran, 2009

Asthma is one of the most common chronic diseases that in some cases it is manifested as chronic coughs without any other symptoms. Cough variant asthma (CVA) is an occult form of asthma of which, the only sign or symptom is chronic cough and therefore should always be considered in the differential diagnosis of chronic coughs. The aim of the present study was to detect the prevalence of cough variant asthma (CVA) among patients with chronic and persistent coughs. This study was performed in the respiratory outpatient clinic at Vali-e Asr Hospital of Zanjan, Iran, during 2009. Methacholine challenge test was carried out in 92 patients suffering from chronic coughs. CVA was diagnosed as chronic coughs without wheezing or any apparent cause which had persisted for more than 8 weeks, with a normal CXR and spirometry but with bronchial hyper-responsiveness to methacholine, based on % 20 drop in FEV1 before and after methacholine challenge test. Of the 92 patients suffering from chronic cough, 24 patients (%26.1) satisfied the criteria for CVA and had positive methacholine challenge test. There was a significant association between patient's job (P=0.003) and education (P=0.001) and positive test. These findings suggest that CVA is a common etiology for chronic cough and its early diagnosis and treatment is significantly important to prevent progression of the disease to classic asthma.