Breath-based stratification of asthma severity using the MISTRAL platform with integrated H2S sensor and clinical validation

Exhaled breath analysis offers a painless window into airway inflammation, yet its clinical adoption is limited by a shortage of robust biomarkers. Hydrogen sulfide () has been detected in biological fluids, but its diagnostic value across asthma severities is not well established. In this study, we integrated an electrochemical sensor with a detection limit of 1 ppb into the MISTRAL platform. We evaluated exhaled in a prospective cohort of 28 adult asthmatic patients. Mean exhaled concentrations were significantly higher in individuals with mild-to-moderate asthma () than in those with severe asthma (; one‑tailed t‑test,). In early-stage disease, levels negatively correlated with maximal expiratory flow MEF, with a similar trend for MEF, whereas in severe asthma, positive but not fully statistically significant correlations emerged with FEV/FVC ratio, and vital capacity VC. These findings reveal a biphasic pattern: elevated may signify a compensatory antioxidant response that collapses as damage in the medium-to-peripheral airways progresses. The plug-and-play MISTRAL platform thus enables real-time, point-of-care assessment of exhaled as a promising, and complementary biomarker to FeNO and blood eosinophil count, offering a rapid, non-invasive indicator of disease control, treatment responsiveness, and exacerbation risk.