Nasal exudate sampling for GFAP determination: A comparative study of collection devices and recovery methods for point-of-care stroke diagnosis

The discovery of a brain-nose discharge through the glymphatic clearance pathway across the cribriform plate has opened new possibilities for biomarker-based diagnostics of neurological disorders. Glial fibrillary acidic protein (GFAP) is a clinically relevant biomarker for early differentiation between hemorrhagic and ischemic stroke, yet its low abundance in nasal exudate (NE) poses significant analytical challenges. Current nasal sampling devices and processing workflows are commonly aimed at infectious respiratory diseases, where analyte concentrations are substantially higher. In this study, three NE collection devices (flocked nylon swabs, GrooveSwab Ⓡ , and Nasosorption™ swabs) have been evaluated alongside multiple recovery protocols for their effectiveness in recovering GFAP from NE. Flocked nylon swabs demonstrated superior protein recovery and patient comfort, making them the most appropriate option for GFAP determination. In contrast, although GrooveSwab Ⓡ and Nasosorption™ swabs exhibited lower protein recovery, they showed potential for applications involving higher analyte concentrations or alternative diagnostic formats. Recovery protocols combining vortexing and centrifugation provided the highest GFAP release with minimal losses. Overall, these findings support the feasibility of decentralized NE sampling for GFAP determination and highlight its potential integration into rapid, minimally invasive point-of-care workflows for stroke diagnosis.