Exhaled biomarkers in adults with non-productive cough

Abstract

<b>Background:</b> Chronic cough is a common condition but the disease mechanisms are not fully understood. <b>Aim:</b> To study respiratory biomarkers from the small airways in individuals with chronic cough. <b>Methods:</b> A general population cohort of 107 participants answered detailed questionnaires, performed spirometry, exhaled NO measurement, impulse oscillometry, gave blood samples and particles in exhaled air (PExA) samples. Current smokers (N=38) were excluded. A total of 12 participants reported chronic non-productive cough and were non-smokers (cases). A total of 55 participants reported no cough and were non-smokers (control group). PExA samples, previously shown to be derived from small airways, were analysed with the SOMAscan proteomics platform. <b>Results:</b> Participants with chronic cough had similar age, sex distribution, BMI, and inflammation markers in blood tests, compared with participants without cough. The proteomics analysis found&nbsp;59 proteins significantly altered among participants&nbsp;with chronic cough compared to controls, after&nbsp;adjusting for age,&nbsp;sex&nbsp;and&nbsp;investigator performing the PExA measurement&nbsp;(all with&nbsp;p-value &lt;0.05 and q-value ≤0.17). This included proteins such as complement factor H (2.5-fold increase), coagulation factor IX (1.8-fold increase), fibrinogen (1.9-fold increase), prothrombin (2.0-fold increase), and immunoglobulin A (1.9-fold increase). <b>Conclusions:</b> This exploratory study on proteomics of exhaled particles among individuals with chronic cough found alterations in 59 proteins. Many of them are involved in&nbsp;immune response and inflammatory pathways, as well as&nbsp;complement activation. Further studies are needed to explore the importance of these findings.