Blood eosinophil count as a predictor of treatment response in adult patients with chronic cough

Abstract

The new 2019 ERS guidelines on the diagnosis and treatment of chronic cough (CC) reported the lack of evidence on the role of blood eosinophil count (BEC) as a predictor of treatment response. The study was aimed to assess a relationship between BEC and the efficacy of CC treatment. Data on 142 non-smoking patients with CC and a normal chest x-ray, prospectively observed between 2014 and 2019, were analyzed. At least a 20 mm decrease in CC severity measured in visual analogue scale (VAS) was classified as good response to CC treatment. Receiver operating characteristic (ROC) curve was constructed to evaluate usefulness of BEC for prediction of treatment response. Correlation between BEC and reduction of CC severity was analyzed using Spearman9s rank correlation coefficient. Asthma, rhinitis and gastroesophageal reflux were diagnosed in 49.3%, 41.6% and 47.9% of patients, respectively. Causative treatment was applied to all these patients. A weak positive correlation was found for reduction in CC severity and BEC in all patients (r=0.2276, p=0.006). Area under the ROC curve was 0.614 ([95% CI] 0.52–0.71) with the optimal BEC cut off level for predicting treatment response set at 237/µL (Youden Index 0.23). Patients with elevated BEC ([≥237/µL], 29.6%) had a greater improvement in quality of life in Leicester Cough Questionnaire (LCQ) and a greater decrease in CC severity (3.9 points vs 2.2 points in LCQ, p=0.03 and 36 mm vs 13 mm in VAS, p=0.01) compared to those with low BEC ( BEC is a poor predictor of response to therapy in patients with CC.