LAUSR

Background Many patients with cough variant asthma (CVA) are underdiagnosed and undertreated due to the atypical symptoms, low diagnostic sensitivity of bronchodilator response (BDR), and limited application of bronchial challenge test. Objective To investigate whether airway reversibility in BDR can predict CVA diagnosis in patients with chronic cough and negative BDR. Methods This open-label, prospective cohort study included patients with chronic cough, nearly normal chest CT scan, and negative BDR results. Inhaled corticosteroids and long-acting β2 agonists were given for 4 weeks. The confirmed diagnosis of CVA was defined as improved symptoms and an increase of forced expiratory volume in 1 s (FEV1) by >12% and >200 mL after 4 weeks of treatment. Results Of 155 patients recruited, 140 completed the study. Patients in the CVA positive diagnosis group had greater absolute (Δ) and percent (Δ%) improvements in FEV1 and forced expiratory flows (FEFs), and higher fractional exhaled nitric oxide (FENO) than in the CVA negative diagnosis group. The area under the receiver operating characteristic curves (AUCs) of ΔFEV1%, FEF25–75%pred (percentage of predicted forced expiratory flow at 25% to 75%) and FENO for CVA positive diagnosis was 0.825, 0.714, and 0.637, with cutoff values of 5.90%, 61.99% and 41.50 ppb, respectively. A joint model of ΔFEV1% combined with FEF25–75%pred or FENO increased the AUC to 0.848 and 0.847, respectively. Conclusion ΔFEV1% in BDR can predict a CVA diagnosis and response to anti-asthma treatment in patients with chronic cough and negative BDR. Clinical trial registration [http://www.chictr.org.cn/index.aspx], identifier [ChiCTR2000029065].