Predictive Value of Modifications of the Prehospital Rapid Arterial Occlusion Evaluation Scale for Large Vessel Occlusion in Patients with Acute Stroke

Background

Prehospital clinical scales to identify patients with acute stroke with a large vessel occlusion (LVO) and direct them to an endovascular-capable stroke center are needed. We evaluated whether simplification of the Rapid Arterial oCclusion Evaluation (RACE) scale, a 5-item scale previously validated in the field, could maintain its high performance to identify patients with LVO.

Methods

Using the original prospective validation cohort of the RACE scale, 7 simpler versions of the RACE scale were designed and retrospectively recalculated for each patient. National Institutes of Health Stroke Scale score and proximal LVO were evaluated in hospital. Receiver operating characteristic analysis was performed to test performance of the simplified versions to identify LVO. For each version, the threshold with sensitivity closest to the original scale (85%) was used, and the variation in specificity and correct classification were assessed.

Results

The study included 341 patients with suspected stroke; 20% had LVO. The 7 simpler versions of the RACE scale had slightly lower area under the curve for detecting LVO because of lower specificity at the chosen sensitivity level. Correct classification rate decreased 9% if facial palsy was simplified or if eye or gaze deviation was removed, and decreased 4.5% if the aphasia or agnosia cortical sign was removed.

Conclusions

We recommend the original RACE scale for prehospital assessment of patients with suspected stroke for its ease of use and its high performance to predict the presence of a LVO. The use of simplified versions would reduce its predictive value.

Introduction

Mechanical thrombectomy substantially reduces disability in patients with large vessel occlusion (LVO) ischemic stroke in the anterior circulation.1, 2, 3, 4, 5 However, benefit declines with increasing time after symptom onset.⁶ Transferring patients from a primary stroke center to a comprehensive stroke center (CSC) commonly delays endovascular treatment.⁷ A prehospital clinical tool to detect patients with LVO and facilitate rapid transport directly to a comprehensive stroke center is therefore of crucial importance.

The National Institutes of Health Stroke Scale (NIHSS) can identify patients with an LVO, but the optimal cut point is controversial, and it is too complex and time-consuming to be used by prehospital emergency medical services (EMS). Other scales may identify patients with LVO, but these scales have not been validated prospectively or in the field.8, 9, 10, 11, 12 The Rapid Arterial oCclusion Evaluation (RACE) scale is simple and specifically designed to identify patients with anterior circulation LVO (Table 1). In prospective prehospital validation by EMS, a RACE scale score ≥5 had 85% sensitivity and 68% specificity for LVO.¹³ The RACE scale has been externally validated as one of the most accurate clinical scales to detect LVO.¹⁴

Scoring RACE is easy and fast.¹³ However, it could be argued that it is more complex than other scales. We evaluated whether simplification of the RACE scale would maintain its high performance to predict LVO.