Rapid Arterial Occlusion Evaluation Scale Research Articles

Clinical benefit of improved Prehospital stroke scales to detect stroke patients with large vessel occlusions: results from a conditional probabilistic model

BackgroundClinical scales to detect large vessel occlusion (LVO) may help to determine the optimal transport destination for patients with suspected acute ischemic stroke (AIS). The clinical benefit associated with improved diagnostic accuracy of these scales has not been quantified.MethodsWe used a previously reported conditional model to estimate the probability of good outcome (modified Rankin scale sore ≤2) for patients with AIS and unknown vessel status occurring in regions with greater proximity to a primary than to a comprehensive stroke center. Optimal rapid arterial occlusion evaluation (RACE) scale cutoff scores were calculated based on time-dependent effect-size estimates from recent randomized controlled trials. Probabilities of good outcome were compared between a triage strategy based on these cutoffs and a strategy based on a hypothetical perfect LVO detection tool with 100% diagnostic accuracy.ResultsIn our model, the additional benefit of a perfect LVO detection tool as compared to optimal transport-time dependent RACE cutoff scores ranges from 0 to 5%. It is largest for patients with medium stroke symptom severity (RACE score 5) and in geographic environments with longer transfer time between the primary and comprehensive stroke center.ConclusionBased on a probabilistic conditional model, the results of our simulation indicate that more accurate prehospital clinical LVO detections scales may be associated with only modest improvements in the expected probability of good outcome for patients with suspected acute ischemic stroke and unknown vessel status.

Abstract WP119: Leukoaraiosis Attenuates Diagnostic Accuracy of Large Vessel Occlusion Scales

Background and Purpose: Preclinical stroke scales may help identify patients likely to have large vessel occlusion (LVO) to facilitate rapid triage to thrombectomy-capable stroke centers. Scale misclassification may result in inaccurate decisions and possible harm. Pre-existing leukoaraiosis has been shown to attenuate the association between deficit type and stroke severity. We sought to determine whether leukoaraiosis affects the predictive ability of 5 commonly used LVO scales. Materials and Methods: We retrospectively analyzed 274 consecutive stroke patients with available brain MRI and vessel imaging. The following LVO scales were used: 3 Item Stroke Scale (3I/SS), Field Assessment Stroke Triage for Emergency Destination (FAST-ED), Rapid Arterial Occlusion Evaluation (RACE), Vision, Aphasia, Neglect (VAN) score, and Cincinnati Prehospital Stroke Severity Scale (CPSSS). For diagnostic scale accuracy, we assessed sensitivity, specificity, positive predictive value, negative predictive value, and kappa. Multivariable logistic regression was used to determine the scales’ predictive ability after adjustment for leukoaraiosis and potential confounders. Results: In unadjusted analyses, all scales predicted LVO (n=46; P<0.01, each), though leukoaraiosis attenuated diagnostic accuracy and was associated with more false negative diagnoses. After adjustment, the FAST-ED (OR 3.2 [1.1-9.5]; P=0.033), and RACE (OR 3.7 [1.3-10.8]; P=0.015) but not 3I/SS (OR 5.4 [0.86-33.9]); P=0.073), VAN (OR 2.5 [0.8-7.2]), and CPSSS (OR 2.8 [1.0-8.0]) predicted LVO. Conclusion: The diagnostic accuracy of the tested LVO scales was attenuated by moderate-tosevere leukoaraiosis. If confirmed, this information may aid acute decision making and the design of studies that require LVO scale screening of patients likely to have concomitant leukoaraiosis.

Abstract 96: Assessment of the Rapid Arterial oCclusion Evaluation (RACE) Scale in Real-World Practice for Prediction of Large Vessel Occlusion and Reducing Time to Thrombectomy

Background: Pre-hospital identification of potential large vessel occlusion (LVO) stroke patients may lead to faster triage and treatment. We examined whether the RACE scale can be reliably implemented in a real-world setting with multiple EMS agencies and lead to rapid treatment. Methods: A prospective study was performed at a high volume comprehensive stroke center. In the first phase, eight EMS agencies were educated on use of the RACE scale using an online training video. All EMS stroke alerts were recorded. When EMS RACE score was 5 or higher, the neurocath lab team was alerted prior to EMS arrival as part of a parallel workflow. Upon ER arrival, the following characteristics were tracked: NIHSS score, RACE score, CT findings, presence of LVO and workflow time metrics. Results: During the study period (January 2016 to June 2017), RACE score was provided for 797 of 1498 EMS stroke alerts (53%). Higher pre-hospital RACE scores correlated with NIHSS scores. LVO was found in 106 (13%) of patients with an available RACE score. A RACE score of 5 or higher was able to identify 64% of all LVO patients (sensitivity: 64%; specificity: 72%; PPV: 30%; NPV: 93%; accuracy: 71%; Youden’s index). However, of the 260 patients with RACE score 5 or higher, only 68 patients (26%) were found to have LVO while 29 patients (11%) had ICH (figure); among 499 patients with RACE score less than 5, LVO was present in 38 patients (8%). When an EMS stroke alert with high RACE score triggered early alert of the neurocath lab team, median door to groin puncture time for thrombectomy was 65 minutes compared to 91 minutes for cases with sequential workflow. Conclusion: The RACE scale can be successfully implemented across EMS agencies and results in faster door to groin puncture times. While a RACE score of 5 or higher is associated with greater likelihood of LVO, there are a significant number of false positives. Further refinement of pre-hospital stroke severity scales is warranted to improve the accuracy of this approach.

Abstract TP239: Initial Results From a Community Emergency Medical System Based Bypass Protocol Using Rapid Arterial Occlusion Scale to Screen for Emergent Large Vessel Occlusion

Introduction: Although mechanical thrombectomy (MT) is the standard of care for patients with acute ischemic stroke due to emergent large vessel occlusion (ELVO), few patients remain eligible for MT due to pre-hospital delays and presentation to non-MT capable hospitals. Emergence of in field screening tools have allowed EMS to reliably identify patients with likely ELVO, thus facilitating their direct triage to MT capable hospitals for prompt thrombectomy. Methods: In collaboration with the Peninsulas EMS Council (PEMS), we implemented a community based pilot program in the Hampton Roads region of Southeastern Virginia to identify patients with ELVO by utilizing the Rapid Arterial oCclusion Evaluation (RACE) scale, a validated in field screening tool. Under this protocol, since March 1 st , 2017, patients with a RACE score of ≥ 5, presenting within 6 hours of last known well would be transported directly to a Comprehensive Stroke Center (CSC) rather than a Primary Stroke Center (PSC), provided the bypass does not prolong the trip by more than 15 minutes. We present the initial results of this study including iv tPA and MT treatment rates, time metrics, and patient outcomes, in comparison to the pre-RACE protocol data. Results: Between March 1 st and June 30 th , 2017, of the 75 brain attacks received in our CSC, 45 patients were screened using the RACE scale by the EMS. 30 patients scored ≥ 5 on the RACE scale (RACE +) and 21 of those bypassed PSCs on their way. RACE + patients had a higher median NIHSS (16 vs. 6, p < .0 5 ), and ischemic strokes (70% vs. 58%), compared to the non-RACE + patients in the preceding 4 months. Improved time metrics (median) were observed for symptom onset to arrival (54 min vs. 81 min), arrival to CT (8.5 min vs. 12 min, p < .05), DTN (36 min vs. 47 min), DTG (94 min vs. 105 min), and arrival to recanalization with MT (142 min vs. 185 min). IV tPA (27% vs. 11%) and MT treatments rates (33% vs. 11%) with TICI ≥ 2b (90% vs. 77%) were higher in the RACE + patients compared to the non-RACE + cohort. Conslusion: Our pilot program employing RACE as an in field screening tool for ELVO and using it to bypass PSCs in favor of CSCs is feasible in the community setting, and demonstrates improved metrics in key domains known to be associated with better outcomes for these patients.

Abstract 138: How Far is Too Far? A Decision Analysis Model of Pre-hospital Triage for Potential Large Vessel Occlusion Acute Stroke Patients

Background and Purpose: We sought to determine when transporting patients directly to a comprehensive stroke center (CSC; the “mothership”) is favorable compared to a “drip-and-ship” approach while accounting for the varying predictive abilities of pre-hospital large vessel occlusion (LVO) screening methods. Methods: We built a decision analysis model to compare anticipated functional outcomes for patients who are within IV-tPA treatment window in “mothership” and “drip-and-ship”. Key branches included IV-tPA eligibility, IV-tPA only or endovascular therapy (ET), successful reperfusion after ET, and treatment effects. In terms of the probability of requiring ET, we assessed three pre-hospital LVO screening methods: no LVO screening, the Rapid Arterial oCclusion Evaluation (RACE) Scale for Stroke, and in-ambulance CT angiography for LVO. Good outcome was defined as mRS 0-1 and, secondarily, mRS 0-2. Imputed probabilities and workflow times were extracted from published studies. We used one-way and two-way sensitivity analyses to vary two key inputs: time from onset to arrival at primary stroke center (PSC) and additional travel time to CSC. Results: The relative benefit of the “mothership” approach varied with the likelihood of pre-hospital LVO identification for outcome of mRS 0-1. In the absence of pre-hospital LVO screening, “drip-and-ship” was always favored. When pre-hospital CT angiography is used, “mothership” is always favored. When modeling the use of the RACE Scale for patients with onset-to-PSC arrival time less than 70 minutes, “mothership” was favored if the additional travel time to CSC was less than 21 minutes. When onset-to-PSC arrival time passed 70 minutes, “mothership” was favored for additional travel times up to 48 minutes (Figure). Conclusion: The results of our decision analysis model suggest that, in addition to transport times, pre-hospital LVO screening and time from stroke onset could influence triage decision making.

Impact of Prehospital Triage Scales to Detect Large Vessel Occlusion on Resource Utilization and Time to Treatment.

Prehospital stroke severity scales may help to triage acute ischemic stroke patients with large vessel occlusion (LVO) for direct transportation to a comprehensive stroke center. The impact on resource use and time to reperfusion treatment for patients with and without LVO is unknown. Based on empirical distributions of stroke symptom severity, prehospital delay times, and stroke symptom severity-dependent likelihood of LVO, we simulate prehospital incidents of stroke-like symptoms in abstract geographical environments to estimate the impact of prehospital triage strategies based on different cutoffs of the rapid arterial occlusion evaluation scale. Compared with transporting each patient to the nearest stroke center, implementation of a prehospital triage strategy based on a rapid arterial occlusion evaluation scale cutoff score ≥5 is associated with more patients with suspected acute stroke at comprehensive stroke centers and less patients at primary stroke centers (+11.7% [95% confidence interval: +8.1% to +15.3%] and -18.4% [-19.1% to -17.7%], respectively). Mean time to groin puncture is reduced by 29.6 minutes (-35.2 to -24.7 minutes) while mean time to thrombolysis does not change significantly (±0.0 minutes [-0.3 to +0.3 minutes]). The total number of secondary transfers is reduced by 60.9% (-62.8% to -59.0%); mean time of ambulance use per patient is unchanged. Results are robust with regards to variation in model parameters. Implementation of prehospital triage based on stroke severity scales would have strong impact on patient flow and distribution. The benefit of earlier thrombectomy for patients with LVO may outweigh the harm associated with delayed access to thrombolysis for some patients without LVO. Randomized trials using clinical stroke severity scales as a triage tool are needed to confirm our findings.

Derivation and Validation of the Emergency Medical Stroke Assessment and Comparison of Large Vessel Occlusion Scales

This study aims to develop a simple scale to identify patients with prehospital stroke with large vessel occlusion (LVO), without losing sensitivity for other stroke types. The Emergency Medical Stroke Assessment (EMSA) was derived from the National Institutes of Health Stroke Scale (NIHSS) items and validated for prediction of LVO in a separate cohort. We compared the EMSA with the 3-item stroke scale (3I-SS), Cincinnati Prehospital Stroke Severity Scale (C-STAT), Rapid Arterial oCclusion Evaluation (RACE) scale, and Field Assessment Stroke Triage for Emergency Destination (FAST-ED) for prediction of LVO and stroke. We surveyed paramedics to assess ease of use and interpretation of scales. The combination of gaze preference, facial asymmetry, asymmetrical arm and leg drift, and abnormal speech or language yielded the EMSA. An EMSA less than 3, 75% sensitivity, and 50% specificity significantly reduced the likelihood of LVO (LR- = .489, 95% confidence interval .366-0.637) versus 3I-SS less than 4 (.866, .798-0.926). A normal EMSA, 93% sensitivity, and 47% specificity significantly reduced the likelihood of stroke (LR- = .142, .068-0.299) versus 3I-SS (.476, .330-0.688) and C-STAT (.858, .717-1.028). EMSA was rated easy to perform by 72% (13 of 18) of paramedics versus 67% (12 of 18) for FAST-ED and 6% (1 of 18) for RACE (χ2 = 27.25, P < .0001), and easy to interpret by 94% (17 of 18) versus 56% (10 of 18) for FAST-ED and 11% (2 of 18) for RACE (χ2 = 21.13, P < .0001). The EMSA has superior abilities to identify LVO versus 3I-SS and stroke versus 3I-SS and C-STAT. The EMSA has similar ability to triage patients with stroke compared with the FAST-ED and RACE, but is simpler to perform and interpret.

Optimal Transport Destination for Ischemic Stroke Patients With Unknown Vessel Status: Use of Prehospital Triage Scores.

Patients with acute ischemic stroke (AIS) and large vessel occlusion may benefit from direct transportation to an endovascular capable comprehensive stroke center (mothership approach) as opposed to direct transportation to the nearest stroke unit without endovascular therapy (drip and ship approach). The optimal transport strategy for patients with AIS and unknown vessel status is uncertain. The rapid arterial occlusion evaluation scale (RACE, scores ranging from 0 to 9, with higher scores indicating higher stroke severity) correlates with the National Institutes of Health Stroke Scale and was developed to identify patients with large vessel occlusion in a prehospital setting. We evaluate how the RACE scale can help to inform prehospital triage decisions for AIS patients. In a model-based approach, we estimate probabilities of good outcome (modified Rankin Scale score of ≤2 at 3 months) as a function of severity of stroke symptoms and transport times for the mothership approach and the drip and ship approach. We use these probabilities to obtain optimal RACE cutoff scores for different transfer time settings and combinations of treatment options (time-based eligibility for secondary transfer under the drip and ship approach, time-based eligibility for thrombolysis at the comprehensive stroke center under the mothership approach). In our model, patients with AIS are more likely to benefit from direct transportation to the comprehensive stroke center if they have more severe strokes. Values of the optimal RACE cutoff scores range from 0 (mothership for all patients) to >9 (drip and ship for all patients). Shorter transfer times and longer door-to-needle and needle-to-transfer (door out) times are associated with lower optimal RACE cutoff scores. Use of RACE cutoff scores that take into account transport times to triage AIS patients to the nearest appropriate hospital may lead to improved outcomes. Further studies should examine the feasibility of translation into clinical practice.

Abstract WP277: Race Score is Scalable to Other Ems Systems; A Sensitivity Analysis

Back Ground: Rapid Arterial Occlusion Evaluation Scale (RACE) was first instituted in Barcelona and described in 2014 to successfully assess stroke severity and identify patients with acute stroke with large vessel occlusion (LVO) at pre-hospital setting by medical emergency technicians. Objective: We instituted Rapid Arterial Occlusion Evaluation Scale (RACE) hospital bypass protocol (RA) in Lucas county, Ohio since July 2015. Our aim in this study is to evaluate the sensitivity of our RACE protocol in identifying cerebro-vascular accidents and furthermore to identify ischemic CVAs from the cohort. Method: All county EMS personnel (N=464) underwent training in the Rapid Arterial Occlusion Evaluation (RACE) score. The RACE Alert (RA) protocol, whereby patients with stroke symptoms, who were last seen normal less than 12 hours and had a RACE score ≥5 were taken to a facility that has neuro-interventional capacity, was implemented in July 2015. An IRB approved prospective DB was maintained during that period. Patient’s stroke characteristics, type of acute treatment and final diagnosis on discharge were reviewed for the purpose of this abstract. Our results were comparable to the Spanish study done in Barcelona in 2014. Results: Between Jul 2016-Jun 2016 186 RAs were activated. The discharge diagnoses included ischemic stroke N=91 (49%), ICH N=26 (14%) and TIA N=17(9%). The rate of stroke mimic was N=52 (28%) of the total RACE alerts. These included seizures (12%), metabolic encephalotpathy (12%) and others including sepsis and migraines. Of the patients presenting as RA, 33% underwent IV tPA treatment ± mechanical thrombectomy. Conclusion: Results from our prospective county wide data is comparable to prior studies. RACE score may be scalable to other EMS systems to triage potential LVOs for direct transfer to centers with interventional capabilities.

Abstract TP253: A Novel Prehospital Scale to Predict Candidates for Acute Stroke Thrombectomy : The Fukuoka Acute Stroke ThrombEctomy pRediction (FASTER) Scale

Background: We aimed to design a prehospital scale to predict candidates for endovascular thrombectomy (CET) in patients with acute ischemic stroke (AIS). Materials and methods: In the Fukuoka Stroke Registry, we identified 3,470 patients with AIS who were transferred by emergency medical service within 24 hours of stroke onset and underwent intracranial vessel evaluation on admission from September 2007 to December 2015. CET were defined as patients with causative occlusion of internal carotid artery, middle cerebral artery, or basilar artery, and National Institute of Health Stroke Scale (NIHSS) score ≥ 6. The Fukuoka Acute Stroke ThrombEctomy pRediction (FASTER) scale was developed with NIHSS items based on the predictive importance derived from random forest analysis to predict CET. The discriminative performance was compared with other published scales for large vessel occlusion. Results: The FASTER scale was designed comprising of 4 NIHSS items : one point each was given for extinction and inattention (NIHSS subscore ≥ 1), best gaze (≥ 1), best language (≥ 1), and motor arm (≥ 2). Receiver operator curves demonstrated that the area under the curve of the FASTER scale was significantly larger than that of the Cincinnati Prehospital Stroke Severity Scale (0.907 vs 0.881, p&lt;0.001), and not significantly different from that of the Rapid Arterial oCclusion Evaluation scale (vs 0.910, p= 0.68). The FASTER scale score ≥2 showed sensitivity of 88.4%, specificity 82.3%, positive predictive value 51.3%, and negative predictive value 97.1% for detecting CET. Conclusion: The FASTER scale is a simple and promising tool that can identify CET in the prehospital setting.

Abstract NS2: RACE to Treat Stroke: The Results

Background: In June of 2015 we revised the County-Level Emergency Medical Services (EMS) protocol and algorithm to include the Rapid Arterial oCclusion Evaluation (RACE) scale in addition to the Cincinnati Prehospital Stroke Scale (CPPS) to determine if first responders could differentiate between which stroke patients could benefit from endovascular treatment using this simple algorithm. Preliminary data showed that first responders can accurately differentiate between which stroke patients could benefit from endovascular treatment but does it increase treatment rates and decrease treatment times? Purpose: To determine if first responders transporting stroke patients to the closest Interventional Stroke Center for treatment increased the number of stroke patients receiving interventional treatment and/or intravenous tissue plasminogen activator (IV tPA) and does door to needle and door to computerized axial tomography scan (CT) times decrease? Method: We analyzed the number of thrombectomies done and the number of patients receiving IV tPA from July 2014 to June 2015 (before implantation of the RACE protocol) compared to July 2015 to June 2016 (after implantation of the RACE protocol) and examined our door to needle and door to CT scan times over the same period. Results: EMS brought 56 ischemic stroke patients to our primary stroke center from July 2014 to June 2015. 10 patients received IVtPA (17.8%) and 5 underwent thrombectomies (8.9%). EMS brought 83 ischemic stroke patients to our primary stroke center from July 2015 to June 2016 using the RACE protocol. 29 patients received IVtPA (34.9%) and 18 underwent thrombectomies (21.7%). Our door to needle times for IVtPA decreased from a median of 64 minutes to 37 minutes, and door to CT times decreased from a median of 24 minutes to 13 minutes over the same time period. Conclusion: Our data suggests that if first responders transport patients using the RACE protocol, a greater percentage of stroke patients will be eligible for endovascular treatment and use of IV tPA and treatment times can also be improved. Future evaluation could measure the outcomes of these patients using the Modified Rankin Score (mRS).

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

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. 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. 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. 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.

Field Assessment Stroke Triage for Emergency Destination

Patients with large vessel occlusion strokes (LVOS) may be better served by direct transfer to endovascular capable centers avoiding hazardous delays between primary and comprehensive stroke centers. However, accurate stroke field triage remains challenging. We aimed to develop a simple field scale to identify LVOS. The Field Assessment Stroke Triage for Emergency Destination (FAST-ED) scale was based on items of the National Institutes of Health Stroke Scale (NIHSS) with higher predictive value for LVOS and tested in the Screening Technology and Outcomes Project in Stroke (STOPStroke) cohort, in which patients underwent computed tomographic angiography within the first 24 hours of stroke onset. LVOS were defined by total occlusions involving the intracranial internal carotid artery, middle cerebral artery-M1, middle cerebral artery-2, or basilar arteries. Patients with partial, bihemispheric, and anterior+posterior circulation occlusions were excluded. Receiver operating characteristic curve, sensitivity, specificity, positive predictive value, and negative predictive value of FAST-ED were compared with the NIHSS, Rapid Arterial Occlusion Evaluation (RACE) scale, and Cincinnati Prehospital Stroke Severity (CPSS) scale. LVO was detected in 240 of the 727 qualifying patients (33%). FAST-ED had comparable accuracy to predict LVO to the NIHSS and higher accuracy than RACE and CPSS (area under the receiver operating characteristic curve: FAST-ED=0.81 as reference; NIHSS=0.80, P=0.28; RACE=0.77, P=0.02; and CPSS=0.75, P=0.002). A FAST-ED ≥4 had sensitivity of 0.60, specificity of 0.89, positive predictive value of 0.72, and negative predictive value of 0.82 versus RACE ≥5 of 0.55, 0.87, 0.68, and 0.79, and CPSS ≥2 of 0.56, 0.85, 0.65, and 0.78, respectively. FAST-ED is a simple scale that if successfully validated in the field, it may be used by medical emergency professionals to identify LVOS in the prehospital setting enabling rapid triage of patients.

Clinical Scales Do Not Reliably Identify Acute Ischemic Stroke Patients With Large-Artery Occlusion.

It remains debated whether clinical scores can help identify acute ischemic stroke patients with large-artery occlusion and hence improve triage in the era of thrombectomy. We aimed to determine the accuracy of published clinical scores to predict large-artery occlusion. We assessed the performance of 13 clinical scores to predict large-artery occlusion in consecutive patients with acute ischemic stroke undergoing clinical examination and magnetic resonance or computed tomographic angiography ≤6 hours of symptom onset. When no cutoff was published, we used the cutoff maximizing the sum of sensitivity and specificity in our cohort. We also determined, for each score, the cutoff associated with a false-negative rate ≤10%. Of 1004 patients (median National Institute of Health Stroke Scale score, 7; range, 0-40), 328 (32.7%) had an occlusion of the internal carotid artery, M1 segment of the middle cerebral artery, or basilar artery. The highest accuracy (79%; 95% confidence interval, 77-82) was observed for National Institute of Health Stroke Scale score ≥11 and Rapid Arterial Occlusion Evaluation Scale score ≥5. However, these cutoffs were associated with false-negative rates >25%. Cutoffs associated with an false-negative rate ≤10% were 5, 1, and 0 for National Institute of Health Stroke Scale, Rapid Arterial Occlusion Evaluation Scale, and Cincinnati Prehospital Stroke Severity Scale, respectively. Using published cutoffs for triage would result in a loss of opportunity for ≥20% of patients with large-artery occlusion who would be inappropriately sent to a center lacking neurointerventional facilities. Conversely, using cutoffs reducing the false-negative rate to 10% would result in sending almost every patient to a comprehensive stroke center. Our findings, therefore, suggest that intracranial arterial imaging should be performed in all patients with acute ischemic stroke presenting within 6 hours of symptom onset.

Abstract 104: The Field Assessment Stroke Triage for Emergency Destination (FAST-ED): a Simple and Accurate Pre-hospital Scale to Detect Large Vessel Occlusion Strokes

Background: Intravenous tPA has a limited efficacy in large vessel occlusion strokes (LVOS). Thus LVOS patients may be better served by direct transfer to endovascular capable centers. We aimed to develop a field scale to identify LVOS. Methods: The FAST-ED scale was designed based on items of the NIHSS with higher predictive value for LVOS: Facial Palsy (scored 0-1), Arm Weakness (0-2), Speech Changes (0-2), Eye Deviation (0-2), and Denial/Neglect (0-2). The scale was tested in the STOPStroke cohort, a prospective study of patients who underwent CT angiography (CTA) within the first 24 hours of stroke onset. LVOS were defined by total occlusions involving the ICA-T, MCA-M1, MCA-2, or basilar arteries. Patients with partial, bi-hemispheric, and/or anterior + posterior circulation occlusions were excluded. Receiver operating characteristic (ROC) curve, sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of FAST-ED were compared with the Rapid Arterial oCclusion Evaluation (RACE) scale and Cincinnati Prehospital Stroke Severity Scale (CPSSS). Results: LVO was detected in 240 out of the 727 qualifying patients (33%). FAST-ED had a strong correlation with NIHSS (r=0.92; P&lt;0.001). FAST-ED had comparable accuracy to predict LVO to the more complex NIHSS and higher accuracy than RACE and CPSS (area under the ROC curve: 0.81, 0.80, 0.77 and 0.75 respectively). Better performance of FAST-ED could be shown at two distinct thresholds depending on the desired sensitivity/specificity trade-offs with scores ≥3 and ≥4 having sensitivity for LVO of 0.71 and 0.60, specificity 0.78 and 0.89, PPV 0.62 and 0.72, and NPV 0.84 and 0.82 versus RACE ≥5 of 0.55, 0.87, 0.68, 0.79 and CPSS ≥2 of 0.56, 0.85, 0.65, 0.78, respectively. Conclusions: FAST-ED is a simpler field scale that can be used by medical emergency professionals to accurately identify LVOS in the pre-hospital setting enabling rapid triage of patients to primary vs. endovascular capable stroke centers.

Abstract 26: RACE to Treat Stroke

Background: Endovascular treatment was shown to drastically improve stroke patient outcomes but earlier identification of eligible patients is crucial. First responders are instrumental to the rapid identification and transportation of stroke patients to the nearest appropriate facility for acute stroke care especially when endovascular intervention is an option. Purpose: To develop and evaluate the effectiveness of an algorithm for first responders to use to differentiate which stroke patients should be transported to the closest Interventional Stroke Center for treatment. Method: We revised the County-Level Emergency Medical Services (EMS) protocol and algorithm to include the Rapid Arterial oCclusion Evaluation (RACE) scale in addition to the Cincinnati Prehospital Stroke Scale (CPPS). Together these simple in-the-field scales assess stroke severity and identify patients with acute stroke and large artery occlusion in a prehospital setting. Lucas County EMS staff received a four hour block of continuing education with credit on acute stroke, the updated protocol and algorithm, and use of the new RACE scale in addition to the CPPS. Effectiveness of the training and use of the RACE alert was measured by the percent of patients accurately identified with and without large artery occlusion. Results: Training was provided to 450 EMS staff in several in-person sessions in June 2015. The RACE protocol went citywide on July first. Of the 18 patients brought in to our hospital by EMS in July using the RACE protocol, 72% were identified correctly using the tool. Of these, 6 were identified correctly as having large vessel occlusions and 7 were correctly identified as not having large vessel occlusions. The remaining 5 patients transported by EMS were identified as large vessel occlusions, but were not found to have strokes (seizures, intoxication, and conversion disorders). Conclusion: Our data suggests that first responders can accurately differentiate between which stroke patients could benefit from endovascular treatment using a simple algorithm. Future evaluation could measure the relationship between accurate pre-hospital identification and treatment rates.

Design and Validation of a Prehospital Stroke Scale to Predict Large Arterial Occlusion

We aimed to develop and validate a simple prehospital stroke scale to predict the presence of large vessel occlusion (LVO) in patients with acute stroke. The Rapid Arterial oCclusion Evaluation (RACE) scale was designed based on the National Institutes of Health Stroke Scale (NIHSS) items with a higher predictive value of LVO on a retrospective cohort of 654 patients with acute ischemic stroke: facial palsy (scored 0-2), arm motor function (0-2), leg motor function (0-2), gaze (0-1), and aphasia or agnosia (0-2). Thereafter, the RACE scale was validated prospectively in the field by trained medical emergency technicians in 357 consecutive patients transferred by Emergency Medical Services to our Comprehensive Stroke Center. Neurologists evaluated stroke severity at admission and LVO was diagnosed by transcranial duplex, computed tomography, or MR angiography. Receiver operating curve, sensitivity, specificity, and global accuracy of the RACE scale were analyzed to evaluate its predictive value for LVO. In the prospective cohort, the RACE scale showed a strong correlation with NIHSS (r=0.76; P<0.001). LVO was detected in 76 of 357 patients (21%). Receiver operating curves showed a similar capacity to predict LVO of the RACE scale compared with the NIHSS (area under the curve 0.82 and 0.85, respectively). A RACE scale≥5 had sensitivity 0.85, specificity 0.68, positive predictive value 0.42, and negative predictive value 0.94 for detecting LVO. The RACE scale is a simple tool that can accurately assess stroke severity and identify patients with acute stroke with large artery occlusion at prehospital setting by medical emergency technicians.