Abstract TP59: Prehospital Identification Of Acute Ischaemic Stroke With Large Vessel Occlusion

Abstract

Background: The prehospital stroke scale B-FAST (Gaze deviation, Face paresis, Arm weakness, Visual loss and Speech disruptions ) was implemented in the Emergency Medical Services (EMS) in the Western Norway Regional Health Trust (1,1 million catchment population; eight primary stroke centres (PSC) ; two comprehensive stroke centres (CSC)) in 2019 to detect acute ischaemic stroke (AIS) patients with large vessel occlusion (LVO). Prehospital presence of gaze deviation (B-symptom)and at least one FAST symptom, may lead to PSC bypass and proceed directly to a CSC. The aim of the study was to investigate the sensitivity of the B-FAST scale detecting LVO in the prehospital setting. Methods: Retrospective study including patients with at least one B-FAST symptom at EMS arrival. We obtained patient data from all code red stroke dispatches from Emergency Medical Communication Centres (EMCC) and local endovascular treatment (EVT) registries in the period August-December 2020. Variables collected were clinical features, CT examination and reperfusion treatment. Definition of prehospital positive B-FAST was presence of Gaze deviation (B-symptom)and at least one FAST symptom at EMS arrival. Results: We collected data on 643 patients, 59 were diagnosed with a LVO stroke at hospital arrival. In the LVO group, 7 of 59 patients presented with prehospital positive B-FAST, resulting in a sensitivity of 12 %. EVT was performed in 38/59 (64%) cases. Two patients were false negative and positive predictive value was 78%. Specificity was 99% and negative predictive value 83%. Median transfer delay for patients initially admitted to a PSC before transfer to a CSC, was 130 min (IQR 60-167 min). Conclusion: The use of B-FAST by EMS personnel for identification of AIS patients with LVO has a low sensitivity, but presence of gaze deviation predicts LVO stroke with high certainty.