Oxidative potential in the exhaled air (OPEA): a candidate biomarker for respiratory diseases screening

BACKGROUND AND AIM OPEA is a physiological-related metric measured with a photonic sensing system, OPEA analyzer. OPEA must be corrected for the oxidative potential in ambient air (OPAA) as a dimensionless ratio OPEA/OPAA (cOPEA). In a hospital setting, OPEA allowed us distinguishing patients with and without chronic obstructive pulmonary disease, particularly among non-smokers. Using the setting of the Swiss health study, we aimed to assess whether OPEA would be increased in participants with abnormal spirometry parameters and in those who demonstrated an immunity against SARS-CoV-2. We also aimed to estimate OPEA reference interval (RI) necessary for interpreting clinical biomarker values. METHODS Swiss adult residents of the Vaud Canton randomly selected from the Federal Statistical Office’s registries, speaking French or German were included and examined between 1.10.2020 and 31.12.2021. General health status and presence of respiratory diseases were assessed by questionnaire and spirometry. Spirometric results were compared with predicted values and their lower limits of norms for spirometric parameters (LLN) of the Global Lung Function Initiative. Seroprevalence was assessed using Luminex-based test of IgG. cOPEA means were compared using univariate t-test and multivariable regression. RI (lower and upper limit of OPEA values with associated 90%-confidence interval (90%CI) were estimated for the sub-sample of healthy adults by bootstrap, after excluding outliers. RESULTS The study sample included 247 participants. A borderline statistically significant difference in cOPEA was observed in participants with an obstructive syndrome. SARS-CoV-seropositive participants had a significantly higher cOPEA than seronegative participants did. After outlier exclusion, the reference sample included 184 participants and RI partitioning appeared unnecessary. Estimated RI was: 0.88 (90%CI=0.85;0.92); 0.97(90%CI=0.93;1.00). CONCLUSION OPEA could predict some respiratory affections, but needs further validation as a disease predictive biomarker in different settings. Our study sample was small and the estimated RI should be considered as preliminary and further confirmed.