Abstract

Purpose To explore the diagnostic value of fractional exhaled nitric oxide (FeNO), small airway function, and a combined of both in differentiating cough-variant asthma (CVA) from typical asthma (TA). Methods A total of 206 asthma subjects, including 104 CVA and 102 TA, were tested for pulmonary function, bronchial provocation test and FeNO. The correlation between FeNO, small airway function and other pulmonary indicators was analyzed by single correlation and multiple regression analysis. The receiver operating characteristic (ROC) curve was established to evaluate the diagnostic efficiency of FeNO, small airway function, and their combination and to predict the optimal cut-off point. Results All the respiratory function parameters and small airway function indicators in TA group were significantly different from those in CVA group, and FeNO value was significantly higher than that in CVA group. In addition, the area under the ROC curve (AUC) was estimated to be 0.660 for FeNO, 0.895 for MMEF75%/25%, 0.873 for FEF50%, 0.898 for FEF25%, 0.695 for Fres, 0.650 for R5-R20, and 0.645 for X5. The optimal cut-off points of FeNO, MMEF75%/25%, FEF50%, FEF25%, Fres, R5-R20 and X5, were 48.50 ppb, 60.02%, 63.46%, 45.26%, 16.63 Hz, 0.38 kPa·L−1·s−1, and −1.32, respectively. And the AUC of FeNO combined with small airway function indexes FEF25%, Fres, R5-R20, and X5 were prior than single indicators. Conclusion FeNO and small airway function indexes might have great diagnostic value for differentiating CVA from TA. The combination of FeNO and FEF25%, Fres, R5-R20, and X5 provided a significantly better prediction than either alone.

Highlights

  • It is worth noting that in univariate analysis, there was no significant correlation between small airway function and gender or BMI, but in multivariate analysis, MMEF75%/25%, FEF50%, and FEF25% in Typical asthma (TA) were significantly correlated with gender and BMI, while MMEF75%/25% and FEF25% were significantly correlated with gender in Cough-variant asthma (CVA)

  • CVA was mainly characterized as spasm of the small airway, while the large airway was not significantly impaired. e airway inflammation of CVA was less severe than that of TA, and the lung function was manifested as changes in small airway ventilation function, while TA had varying degrees of obstruction in both large and small airways [20]

  • CVA can evolve into TA, and nearly 30% of patients with CVA are found to eventually develop TA, so CVA is considered to be a precursor of TA

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Summary

Introduction

Airway inflammation and reversible airflow limitation are the main pathophysiological characteristics of asthma [1]. Cough-variant asthma (CVA) is a subtype of asthma with chronic cough as a single clinical symptom, without wheezing or dyspnea [2]. Typical asthma (TA) is characterized by recurrent wheezing, chest tightness, or cough, often accompanied by reversible airflow limitation, airway hyperresponsiveness, and airway remodeling [3]. Studies believe that the pathogenesis of CVA is similar to that of TA, which is chronic airway inflammation involving multiple cells [5], and airway inflammation is one of the most common factors that aggravate BHR and cough receptor hypersensitivity [6]

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