Comparison of FEV۱ and PEF Values in Cough Variant Asthma During Methacholine Challenge Test

Background and Objective: 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 FEV۱ and PEF during the methacholine challenge test. Materials and Methods: In this study, we tested a total of ۱۲۰ patients (۱۴-۶۵ 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 rulled out. Spirometry and Peak Flowmetry were done during the methacholine challenge test, then FEV۱ and PEF were recorded. Results: From ۱۲۰ patients, ۴۷ patients (۳۹.۲%) were male and ۷۳ (۶۰.۸%) were female. Thirty three (۲۷.۵%) patients showed a ≥ ۲۰% decrease in FEV۱, while ۳۵ patients (۲۹.۲%) had a ≥ ۲۰% decrease in PEFp. Decreasing values of FEV۱ and PEFp with r=۰.۴۹ and P-value<۰.۰۰۰۱ were significant. Normalization for age, sex, and occupation shows that these factors have no effects on the decrease observed for FEV۱ and PEFp. Conclusion: Based on the correlation ratio for PEFp in comparison with spirometry’s FEV۱, we suggest using peak flowmetry instead of spirometry for diagnosing CVA. According on the ROC_curve, we recommend a ≥ ۱۵.۵% decrease in the level of PEFp with ۷۹% sensitivity and ۶۹% specificity.

Keywords:

Asthma , CVA , FEV۱ , PEF , Methacholine