Abstract Body: Introduction: Glial fibrillary acidic protein (GFAP), highly brain-specific, is emerging as an attractive blood biomarker in acute stroke. GFAP can discriminate stroke type (ischemic stroke (IS), intracerebral hemorrhage (ICH), stroke mimics (SM) in the first hours after stroke onset. Rapid GFAP levels using novel point-of-care technology (results <15 minutes) may also offer insights in IS, particularly among those with unknown onset. In this study, we aim to evaluate the potential of rapid GFAP levels to distinguish among stroke types in acute undifferentiated stroke <24h from onset, as well as provide insights in IS of unknown onset.

Methods: An exploratory analysis of an ongoing prospective study of patients with suspected undifferentiated stroke <24h from onset. Rapid plasma GFAP levels (pg/mL) are measured at hospital arrival using the i-STAT Alinity^® instrument and commercially-available cartridges. Study endpoints include quantitative GFAP levels according to final diagnosis (ICH, IS, SM), time from stroke onset/last seen well (<4.5h, 4.5-24h), and ASPECTS score (8-10 vs. <8).

Results: Among the first 101 patients recruited (mean (±SD) 70.8±14.5 years, 48% female, median (IQR) NIHSS 9 (3-20), median ASPECTS (10 (8-10)), final diagnosis was IS (n=67 (33 LVO)), ICH (n=5), and SM (n=29). Median rapid GFAP levels were highest in ICH (3104 (2088-8622) pg/mL), and differed compared to IS (54 (30-100) pg/mL) and SM (29 (29-42) pg/mL), p<0.001. In IS, 58% patients presented <4.5h from onset, and 28% were wake-up strokes. Rapid GFAP levels were undetectable in 13/39 (33%) of IS <4.5h compared to 3/28 (11%) in IS >4.5h, p=0.03. Median GFAP levels was significantly higher in IS >4.5h (87 (42-134) pg/mL) compared to earlier presentations (44 (29-62) pg/mL, p=0.03). Lastly, median GFAP levels had fairly good discriminative ability to detect ASPECTS <8 (AUC 0.73 (95% CI: 0.55-0.91), p=0.003), with an optimal GFAP cutoff of 77 pg/mL (sensitivity 76.9%, specificity 76.9%).

Conclusion: Rapid GFAP levels using novel point-of-care technology is feasible and show promise in acute stroke management. Beyond discrimination of stroke type, rapid GFAP levels appear to increase during the first 24 hours from IS onset and with extent of ischemic injury. These findings, although preliminary, suggest that rapid GFAP levels may inform treatment decisions in IS of unknown onset as well as optimize prehospital triage of acute undifferentiated stroke <24hours from onset.