Comparison of FEV1 and PEF values in cough variant asthma during methacholine challenge test

Asthma is one of the most common chronic diseases with an increasing prevalence. The cough variant of asthma [CVA] is a latent form of the disease. The aim of this study is to compare the decreasing rates of FEV1 and PEF during the methacholine challenge test. In this study, we tested a total of 120 patients [14-65 years old], whom were referred to the respiratory clinic with complaints of chronic cough, using normal chest and sinus x-ray and spirometry. Also other causes of chronic cough were ruled out. Spirometry and Peak Flowmetry were done during the methacholine challenge test, then FEV1 and PEF were recorded. From 120 patients, 47 patients [39.2%] were male and 73 [60.8%] were female. Thirty three [27.5%] patients showed a >/= 20% decrease in FEV1, while 35 patients [29.2%] had a >/= 20% decrease in PEFp. Decreasing values of FEV1 and PEFp with r=0.49 and P-value<0.000l were significant. Normalization for age, sex, and occupation shows that these factors have no effects on the decrease observed for FEV1 and PEFp. Based on the correlation ratio for PEFp in comparison with spirometry's FEV1, we suggest using peak flowmetry instead of spirometry for diagnosing CVA. According on the ROC curve, we recommend a >/= 15.5% decrease in the level of PEFp with 79% sensitivity and 69% specificity

[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 hyperresponsiveness 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 patients ' 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