Background: Measurement of sputum is used to define airway inflammatory phenotypes. Cough variant asthma (CVA) is considered to be the initial stage of classic asthma (CA). The aim of this study was to describe the association between the different subtypes of CVA and CA.
Methods: A total of 459 patients with CVA and CA were screened for the study. All included patients performed spirometry, underwent a bronchial challenge with methacholine and induced sputum according to the guidelines.
Results: A higher frequency of female patients were found with CVA and the eosinophilic airway inflammation of CVA than in CA and the noneosinophilic airway inflammation of CA (p =0.004 and p =0.024, respectively). Bronchial hyper-responsiveness (BHR) was lower in eosinophilic CVA and CA (p =0.006), while no difference was found in noneosinophilic CVA and CA. Association between the percentage of sputum eosinophils and the FEV₁ level fell below 20% of the baseline value (PD₂₀) in CVA and CA (r= − 0.1245, p =0.0357 and r= − 0.2148, p =0.0014, respectively).
Conclusion: Eosinophilia may be associated with more severe disease, yet there was no difference in spirometry between the eosinophilic and noneosinophilic groups, and the BHR difference was not dramatic.
Keywords: cough variant asthma, airway inflammatory types, sputum induction, bronchial hyper-responsiveness