Exhaled nitric oxide in chronic cough: A good tool in a multi-step approach

Introduction. - The impact of fractional exhaled nitric oxide (FENO) on the management of chronic cough (CC) is still inconclusive. The aim of the present study was to assess whether FENO is a good tool to predict the response to inhaled corticosteroids (ICS) in patients with CC. Methods. - Patients, referred for investigation of CC, had a FENO measurement determined as part of their firstline assessment. A methacholine test was performed as part of a second-line assessement. Patients were assigned to two groups according to their FENO values: a high FENO level group (>= 25 ppb) and a normal FENO level group (< 25 ppb). Results. - One hundred patients were included in the study. High FENO levels were found in 25 patients (25%). The proportion of patients who responded to ICS was significantly greater in the high FENO group compared to the normal FENO level group (86.4% vs 46.3%, P < 0.05). FENO is a good tool to predict ICS response in patients with high FENO levels but a response to ICS cannot be ruled out in patients with normal FENO levels. In patients with normal FENO values, a methacholine test could be an interesting tool for a second-line assessment. Among the 13 patients with a positive methacholine test result, 11 responded to ICS whilst 2 did not. Of the patients with a negative methacholine test result, 3 responded to ICS whilst 13 did not. Conclusion. - FENO may be a more reliable predictor of ICS response when used as part of a multi-step assessment procedure. (C) 2019 SPLF et Elsevier Masson SAS. All rights reserved.