The Cincinnati Prehospital Stroke Scale Compared to Stroke Severity Tools for Large Vessel Occlusion Stroke Prediction

Background: Various screening tools, ranging in complexity, have been developed to predict large vessel occlusion (LVO) stroke in the prehospital setting. Our objective was to determine whether newly-developed LVO stroke scales offer a clinically-meaningful advantage over the Cincinnati Prehospital Stroke Scale (CPSS). Methods: We retrospectively analyzed prehospital patient care records linked with hospital data from 151 EMS agencies in the United States, between January 1, 2018 and December 31, 2018. We compared the CPSS to the Rapid Arterial Occlusion Evaluation (RACE), Los Angeles Motor Scale (LAMS), and the Vision, Aphasia, Neglect (VAN) assessment for LVO prediction. For each stroke scale, we used the intersection of sensitivity and specificity curves to determine optimal prediction cut-points. We used area under the ROC curve and 95% confidence intervals to assess for differences in discriminative ability between scales. Results: We identified 13,596 prehospital records with one or more documented stroke scales of interest. Among these, 4,228 patients were diagnosed with stroke. Over half (57%, n = 2,415) of patients diagnosed with stroke experienced an acute ischemic stroke. Of patients with ischemic stroke, 26% (n = 628) were diagnosed with LVO. A CPSS score of 2 or higher demonstrated sensitivity = 69% and specificity = 78% for LVO. A RACE score of 4 or higher demonstrated sensitivity = 63%, specificity = 73%. A LAMS score of 3 or higher demonstrated sensitivity = 63%, specificity = 72% and a positive VAN score demonstrated sensitivity = 86%, specificity = 65%. Comparing the area under the ROC curve for each scale revealed no statistically significant differences in discriminative ability for LVO stroke. Conclusions: In this large sample of real-world prehospital patient encounters, the CPSS demonstrated similar predictive performance characteristics compared to the RACE, LAMS, and VAN for detecting LVO stroke. Prior to implementing a specific screening tool, EMS agencies should evaluate ease of use and associated implementation costs. Scored 0-3, the simple, widely-used CPSS may serve as a favorable prehospital screening instrument for LVO detection with a cut-point of 2 or higher maximizing the tradeoff between sensitivity and specificity.