Abstract A151: Impact of Prehospital GFAP-Based Diagnosis of Intracerebral Hemorrhage on Functional Outcomes: A Modeling Analysis Integrating INTERACT4 Trial Data

Introduction: Timely differentiation between intracerebral hemorrhage (ICH) and ischemic stroke (IS) in the prehospital setting is essential for guiding early treatment. Point of care serum glial fibrillary acidic protein (GFAP) has emerged as a promising biomarker for prehospital ICH diagnosis. This study modeled the potential impact of GFAP-guided diagnosis combined with early antihypertensive therapy on functional outcomes, using data from the INTERACT4 trial. Methods: Diagnostic performance metrics were derived from GFAP studies identified in a systematic literature search and applied to data on the prevalence of ICH (vs IS ) among all ambulance-transported, hyperacute stroke patients, in the US (26.3%) and China (46.8%). Efficacy outcomes projected at 3m were: freedom from disability (mRS, 0-1); functional independence (mRS 0-2); ambulatory/self-care capable (mRS 0-3); level of disability (mean mRS); and disability-weighted quality of life (UW-mRS). Patient-perceived minimal clinically important difference (MCID) for mRS 0-2 was set at 1.3% and practice-changing MCID at 4.0%. Safety outcomes were mortality and combined severe disability and mortality (mRS 5-6). Results: The systematic search identified 3 ICH-diagnostic GFAP studies (Kalra, Zylyftari, Almubayyidh et al). Pooled analysis showed GFAP performance for distinguishing ICH from IS: sensitivity 81%, specificity 85%. Applied to country-specific ICH prevalences in ambulance transported patients, these performance characteristics resulted in PPV of 66% in US and 83% in China(Table 1). Modeling indicated that GFAP-guided prehospital diagnosis followed by field start of antihypertensive therapy yielded improvements in all efficacy outcomes(Table 2, Figure). For example, in US the rate of functional independence(mRS 0-2) increased from 30.8% without BP-lowering to 35.7% with BP-lowering (absolute benefit 4.9%). In China, rate of functional independence(mRS 0-2) increased from 25.8% to 33% (absolute benefit 7.2%). Safety outcomes also improved, including reductions in 3m mortality by an absolute 2.5% in US and 4.5% in China. Conclusion: Formal modeling indicates that, among ambulance-transported acute stroke patients, prehospital GFAP testing can identify a large subgroup enriched ICH who will benefit from field-initiated antihypertensive therapy at rates exceeding patient and system-level MCIDs. These findings support prospective validation of this treatment strategy in prehospital randomized clinical trials.