Comparison of FEV1 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 FEV1 and PEF during the methacholine challenge test. Materials and Methods: 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 rulled out. Spirometry and Peak Flowmetry were done during the methacholine challenge test, then FEV1 and PEF were recorded. Results: 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<0.0001 were significant. Normalization for age, sex, and occupation shows that these factors have no effects on the decrease observed for FEV1 and PEFp. Conclusion: 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.

Comparison of FEV1 and PEF Values in Cough Variant Asthma During Methacholine Challenge Test Keywords:

Asthma , CVA , FEV1 , PEF , Methacholine