A comparative study on the value of lower airway exhaled nitric oxide combined with small airway parameters for diagnosing cough-variant asthma

Abstract

Background: The diagnosis of cough-variant asthma (CVA) is based on bronchial provocation test, which is challenging to be conducted. Most CVA patients have type 2 airway inflammation and small airway dysfunction. FeNO 200 , reflecting small airway inflammation, may be used to diagnose CVA. Objective: This study aimed to explore and compare the value of lower airway exhaled nitric oxide (FeNO 50 , FeNO 200 , and CaNO) combined with small airway parameters for diagnosing CVA. Methods: Chronic cough patients who attended the clinic from September 2021 to August 2022 were enrolled and divided into CVA group ( n = 71) and non-CVA (NCVA) group ( n = 212). The diagnostic values of FeNO 50 , FeNO 200 , concentration of alveolar nitric oxide (CaNO), maximal mid-expiratory flow (MMEF), forced expiratory flow at 75% of forced vital capacity (FEF 75% ) and forced expiratory flow at 50% of forced vital capacity (FEF 50% ) for CVA were evaluated. Results: FeNO 50 [39(39) ppb versus 17(12) parts per billion (ppb), p 11 ppb contributed strongly for differentiating CVA from chronic cough, especially in patients with small airway dysfunction.