The Finnish Prehospital Stroke Scale Detects Thrombectomy and Thrombolysis Candidates-A Propensity Score-Matched Study

Background: Prehospital stroke triage is challenged by endovascular treatment for large vessel occlusion (LVO) being available only in major stroke centers. Conjugate eye deviation (CED) is closely related to LVO, whereas common stroke signs (face-arm-leg-speech-visual) screen stroke. We hypothesized that combining CED with common stroke signs would yield a prehospital stroke scale for identifying both LVO and stroke in general. Methods and Results: We retrospectively analyzed consecutive patients (n = 856) with prehospital Code Stroke (recanalization candidate). The National Institutes of Health Stroke Scale (NIHSS) and computed tomography were administered to patients on arrival. Computed tomography angiography was performed on patients with NIHSS score of 8 or greater and considered to benefit from endovascular treatment. With random forest analysis and deviance analysis of the general linear model we confirmed the superiority of the NIHSS Best Gaze over other NIHSS items in detecting LVO. Based on this and commonly used stroke signs we presented the Finnish Prehospital Stroke Scale (FPSS) including dichotomized face drooping, extremity weakness, speech difficulty, visual disturbance, and CED. FPSS detected LVO with a sensitivity of 54%, specificity of 91%, positive predictive value of 48%, negative predictive value of 93%, and likelihood ratio of 6.2. Conclusions: Based on CED and universally used stroke signs, FPSS recognizes stroke in general and additionally, LVO as a stroke subtype comparably to other scales intended to detect LVO only. As the FPSS items are dichotomized, it is likely to be easy for emergency medical services to implement.