ABSTRACT NUMBER: ESOC2026A1382 PREHOSPITAL PERFORMANCE OF FAST AND NIHSS IN ACUTE VERTIGO PATIENTS WITH SUSPECTED STROKE—SUBGROUP ANALYSIS FROM THE NORWEGIAN ACUTE STROKE PREHOSPITAL PROJECT (PARANASPP) TRIAL

Abstract Background and aims Acute vertigo in the prehospital setting is diagnostically challenging. Stroke screening tools primarly target anterior circulation strokes, but are also applied in identification of stroke among patients with acute vertigo. This study evaluated the diagnostic performance of FAST and NIHSS in prehospital suspected stroke patients presenting with acute vertigo. Methods Register-based post-hoc subgroup analysis of data from ParaNASPP, a stepped-wedge cluster-randomized trial at Oslo University Hospital implementing prehospital NIHSS, paramedic training and standardized communication. Patients with acute vertigo dispatched under suspected stroke criteria were included. Ambulance and hospital records were reviewed to compare baseline characteristics, symptoms, assess prehospital evaluation and reconstruct FAST and NIHSS scores between vertigo patients with and without stroke. Results Of 801 patients with suspected stroke, 247 (31%) had vertigo. Among these were 82 (33%) diagnosed with stroke/TIA. Stroke patients with vertigo were older (median 75 vs. 65 years; P < 0.001), more often used antiplatelet and antihypertensive therapy (P = 0.023, P = 0.001), and had hypertension (P = 0.003) and atrial fibrillation (P = 0.025) compared with stroke mimics. Among vertigo patients, FAST demonstrated positive predictive value (PPV) of 44% for stroke, compared to 38% for NIHSS. Conclusions FAST and NIHSS showed limited predictive value for stroke in vertigo presentations; FAST tended to under-triage, while NIHSS over-triaged. One-third of suspected stroke patients presenting with vertigo had stroke or TIA. Those with stroke had more vascular risk factors.These findings underscore the need for improved prehospital diagnostic support. Algorithms including stroke risk factors may enhance triage accuracy and should be evaluated in future studies. Conflict of interest Hanna Marie Otterholt Bekkeseth: nothing to disclose. Vilde Teigene Måløy: nothing to disclose. Helge Fagerheim Bugge: nothing to disclose. Mona Guterud: nothing to disclose. Maren Ranhoff Hov: nothing to disclose. Else Charlotte Sandset: nothing to disclose. Karianne Larsen: nothing to disclose. Anette Huuse Farmen: nothing to disclose. Table 1 - belongs to Results Table 2 - belongs to Results