Patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO) should be triaged to an endovascular-capable hospital by the emergency medical service (EMS). We designed a prehospital LVO prediction scale based on EMS assessments. In the derivation cohort, 1157 patients transferred to our hospital by the EMS because of suspected stroke within 24 h of onset were retrospectively examined. Factors associated with AIS due to LVO were identified based on the EMS assessment, and a prehospital scale identifying LVO was developed. The accuracy of this scale was validated in 502 consecutive patients who were transferred to 4 stroke centers, and its accuracy was compared with those of 4 previously reported scales. AIS due to LVO was diagnosed in 149 of 1157 patients (13%) in the derivation cohort. One point each was assigned for facial palsy, arm weakness, consciousness impairment (cannot say his/her name), atrial fibrillation, and diastolic blood pressure ≤ 85 mmHg, with two points for conjugate eye deviation (FACE2AD scale). In the derivation cohort, with the optimal cut-point of FACE2AD ≥ 3 determined by the area under the curve (AUC; 0.88; 95% confidence interval 0.87-0.90), sensitivity, specificity, positive predictive value, and negative predictive value for FACE2AD to predict LVO were 0.85, 0.80, 0.39, and 0.97, respectively. In the validation cohort, the FACE2AD scale had higher accuracy, with an AUC value of 0.84 for predicting LVO compared with the other scales (all p < 0.01). The FACE2AD scale is a simple, reliable tool for identifying AIS due to LVO by the EMS.
Keywords: Emergency Medical Service; Ischemic stroke; Large vessel occlusion; Prehospital stroke scale; Triage.