PP31 Use of a lateral flow assay (LVOne) test for ambulance large vessel occlusion stroke recognition and management: feasibility study protocol (RADIOS)

<h3>Background</h3> Rapid diagnosis of large vessel occlusion (LVO) stroke is crucial for timely thrombectomy and optimal patient outcomes. The LVOne test evaluates capillary blood D-dimer and glial fibrillary acidic protein (GFAP) to determine the presence of a cerebral large blood clot. Pre-hospital recognition of a LVO stroke offers opportunities to reduce stroke onset-to-needle time for clot removal. This prospective feasibility study aims to determine the usability and practicality of implementing LVOne tests by ambulance clinicians for suspected stroke patients receiving emergency ambulance care. <h3>Methods</h3> During July – September 2024, 15 ambulance clinicians from one UK ambulance service will deliver the LVOne test to 30 suspected stroke patients. Retrospective research consent will be sought from these patients following hospital admission. Patient inclusion criteria: age ≥ 18yrs; FAST score ≥2; symptom onset ≤ 6hrs, conveyed to thrombectomy-capable hospital. Expert clinician diagnosis will serve as the reference standard for stroke type (ischaemic +/- LVO, intracerebral haemorrhage, transient ischaemic attack or non-stroke mimic). Following LVOne test completion, ambulance clinicians will complete a feasibility questionnaire, the topics will include ease of LVOne delivery; test instructions for use; advice materials; assay interpretation and user confidence. <h3>Results</h3> Ambulance clinicians’ questionnaire responses will be analysed using qualitative approaches to determine the overall feasibility of LVOne during ambulance patient assessment. Overall feasibility will be reported as percentage of positive (‘Yes’) vs negative (‘No’) opinions to the question: ‘Considering your answers above, would you recommend this test for ambulance stroke assessment in the future?’. Acceptance criteria will be that at least 75% answer ‘Yes’ to this question. <h3>Conclusion</h3> This study will provide valuable insights into the feasibility of integrating the LVOne test into pre-hospital stroke evaluation workflows, and the findings will inform the design of future implementation studies to evaluate LVOne test efficacy on ambulance referral to thrombectomy and patient outcomes.