Sputum induction in patients with chronic cough

An ERS NeuroCOUGH CRC site <bold>INTRODUCTION:</bold> Current trends in chronic cough (CC) management focus on distinguishing patients with refractory cough (demanding non-standard therapy) from those who may benefit from causative treatment if treatable traits can be detected. Increased eosinophil count in induced sputum (IS) is a well-established one. <bold>AIM:</bold> We aimed to assess IS results, safety and efficacy of the procedure in patients with CC attending our cough clinic. METHOD: We retrospectively analysed the results of sputum induction (SI) in adult patients with CC > 8 weeks, hospitalized in our cough center between 2019-2023. The percentage of successful procedures, quality of obtained material, safety, and percentage of cells were calculated. <bold>Results:</bold> SI was performed in 272/315 (86%) pts (196 women, mean age 56 years, 43-67) In 10.6% (29/272) no material was obtained, in 44%(121/272) IS was not accurate for assessment. Side effects involved 4 patients (1.4%) and comprised a tingling sensation in the upper limbs (1) and mild bronchoconstriction (3). Increased sputum eosinophilia was detected in 27/122 (22%), median 5% (IQR 4 - 6.5) of eosinophils. In 81/122 (66%) pts an increased percentage of lymphocytes (median 8%, 6-10%) and in 31% sputum neutrophilia (median 63.5, 55-75.27) were observed. <bold>Conclusions:</bold> SI is a safe procedure in CC, but obtaining an accurate sample is not easy. Sputum lymphocytosis in CC is a frequent finding, but its significance demands further evaluation.