Abstract T MP59: Texas Stroke Intervention Pre-Hospital Stroke Severity Scale (aka LEGS score): A Triaging Tool for Interventional Stroke Therapy

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Alexander Venizelos ◽  
Sherman Chen ◽  
Ryan Gianatasio ◽  
Stewart Coffman ◽  
Mark Gamber ◽  
...  
Keyword(s):  
Positive Predictive Value ◽  
Negative Predictive Value ◽  
Predictive Value ◽  
Good Predictor ◽  
Mr Angiography ◽  
Large Vessel ◽  
Stroke Severity ◽  
Large Vessel Occlusion ◽  
Severity Scale ◽  
Vessel Occlusion

Introduction: A pre-hospital stroke severity scale that correlates well with an NIHSS of 10 or greater as well as with large vessel occlusions, but is easier and faster to perform than full NIHSS, would be a very useful triaging tool to emergency medical services (EMS). The LEGS score (Lower extremity strength, Eyes/visual fields, Gaze deviation, Speech difficulty) is a 16-point pre-hospital stroke severity scale that is a shortened NIHSS-5. Hypothesis: We assessed the hypothesis that the LEGS score was a useful pre-hospital stroke severity scoring system to identify large vessel acute ischemic strokes. Methods: The LEGS score (0-16) and NIHSS (0-42) were performed in the emergency department over a 6-month period. We retrospectively reviewed those charts for correlation to an NIHSS of 10 or greater and evidence of large-vessel occlusion on either CT or MR Angiography within 48 hours of last known normal. Results: A total of 181 consecutive ischemic stroke patients were evaluated. LEGS score 4 or greater was a good predictor of an NIHSS of 10 or greater (59/181; positive predictive value 92%; and specificity 95%) and false positives noted was 5/181. LEGS score of less than 4 was a good predictor of an NIHSS of less than 10 (108/181; negative predictive value 91%; and sensitivity 95%) and false negatives noted was 10/181. Of those patients 155 underwent intracranial vascular imaging. LEGS score of less than 4 was a good test to rule-out large vessel occlusion (negative predictive value of 86%; 89/103), but had modest sensitivity (69%; 31/45) and positive predictive value (60%; 31/52). The LEGS score of 4 or greater, however, was fairly specific for determining large-vessel occlusions at 81% (89/110). Conclusions: LEGS score of 4 or greater has good correlation with an NIHSS of 10 or greater as well as modest correlation with large vessel occlusion on CT or MR Angiography. This shortened NIHSS-5 may be a useful pre-hospital indicator of patients who may benefit from endovascular intervention.

Abstract TMP62: Utility of the Los Angeles Motor Scale to Identify Emergency Large Vessel Occlusion in Acute Stroke

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Prasannna Tadi ◽  
Pranav Reddy ◽  
Sravanthi Pemmasani ◽  
Nasir Fakhri ◽  
Matthew Siket ◽  
...  
Keyword(s):  
Los Angeles ◽  
Positive Predictive Value ◽  
Acute Stroke ◽  
Negative Predictive Value ◽  
Predictive Value ◽  
Large Vessel ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
Vessel Imaging ◽  
Los Angeles Motor Scale

Introduction: Stroke is a common medical emergency. The outcome depends upon access to stroke specialists, rapid scanning, assessment, and treatments. Identification of large vessel occlusion (LVO) is critical in the selection of patients for emergency embolectomy (clot removal) in patients with acute ischemic stroke. A pre-hospital stroke severity scale, such as the Los Angeles Motor Scale (LAMS) may have utility in selecting appropriate patients for CTA, while minimizing radiation exposure risk to the population as a whole. Methods: This was a retrospective analysis of 249 consecutive code stroke activations at a comprehensive stroke center during a 3.5 month period using a LAMS cutoff of ≥4 to trigger CTA acquisition. We determined the sensitivity, specificity, positive predictive value, and negative predictive value of using LAMS to detect large vessel occlusion (LVO). Gold standard was any vessel imaging within 24 hours. Inter-rater reliability of LAMS scoring was determined by blinded scoring of physical exam data from the chart by 3 neurovascular physicians. Results: There were 249 code stroke activations during the study period: 91 acute CTAs were recommended based on LAMS scoring. 20 large vessel occlusions were detected. 158 patients did not have a CTA acutely; none had a LVO during subsequent vessel imaging. The sensitivity is 100%, negative predictive value 100%, specificity 69%, positive predictive value 22% of the LAMS triage method. Inter-rater Reliability: Shrout-Fleiss pairwise weighted kappa coefficients between the three raters on LAMS scores were 0.67, 0.55, and 0.62. Kappa coefficients for pairs of raters when LAMS were dichotomized as <3 vs 4-5 were 0.64, 0.50, and 0.71. Clinically meaningful disagreements were evident. Conclusions: Accuracy and ease-of-use makes LAMS an ideal clinical tool to rapidly assess acute stroke patients for LVO and emergency mechanical thrombectomy. LAMS demonstrated excellent sensitivity in excluding patients who did not have a LVO. Appropriate training is required to ensure accuracy of LAMS scoring by providers.

scholarly journals Retrospective Validation of Prehospital Acute Stroke Severity Scale to Predict Large Vessel Occlusion in Acute Stroke Patients - Single Center study in China

2019 ◽  
Author(s):  
Xiaoli Si ◽  
Yuanjian Fang ◽  
Wenqing Xia ◽  
Tianwen Chen ◽  
Huan Huang ◽  
...  
Keyword(s):  
Acute Stroke ◽  
Predictive Value ◽  
Large Vessel ◽  
Motor Deficits ◽  
Stroke Severity ◽  
Large Vessel Occlusion ◽  
Anterior Circulation ◽  
Vessel Occlusion ◽  
Consciousness Disorder ◽  
Gaze Palsy

Abstract Background and Purpose - To date, identifying emergent large vessel occlusion (ELVO) patients in the prehospital stage is important but still challenging. We aimed to retrospectively validate a simple prehospital stroke scale——Prehospital Acute Stroke Severity (PASS) scale to identify ELVO. Methods - We retrospectively evaluated our consecutive cohort of acute ischemic stroke (AIS) who underwent CT angiography (CTA), MR angiography (MRA) or digital subtraction angiography (DSA). PASS scale was calculated based on National Institutes of Health Stroke Scale (NIHSS) items retrospectively. The comparison of diagnostic parameters between PASS scale and NIHSS scale were performed. Results - Finally, a total of 605 patients were enrolled. ELVO patients with PASS≥2 had a median NIHSS score of 14. The best predictive value of PASS≥2 showed a similar predictive value compared with NIHSS≥9. Cortical symptoms such as consciousness disorder and gaze palsy were more specific indicators for ELVO than motor deficits. Consciousness disorder was more serious in posterior circulation infarct (PIC) while gaze palsy was more common in anterior circulation infarct (AIC). Conclusions - PASS scale had both good discrimination and calibration in our retrospective cohort. It could reflect acute stroke severity well and predict ELVO in an effective and simple way. Moreover, cortical symptoms had high specificities to predict ELVO on their own.

scholarly journals Correlation of Alberta Stroke Program Early Computed Tomography Score With Computed Tomography Perfusion Core in Large Vessel Occlusion in Delayed Time Windows

Stroke ◽  
2021 ◽  
Author(s):  
Sriharsha Voleti ◽  
Johnathan Vidovich ◽  
Brendan Corcoran ◽  
Bin Zhang ◽  
Vivek Khandwala ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Positive Predictive Value ◽  
Predictive Value ◽  
Time Windows ◽  
Interquartile Range ◽  
Large Vessel ◽  
Moderate Correlation ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
Delayed Time

Background and Purpose: The Alberta Stroke Program Early Computed Tomography (CT) Score (ASPECTS) and CT perfusion (CTP) are commonly used to predict the ischemic core in acute ischemic strokes. CT angiography source images (CTA-SI) can also provide additional information to identify the extent of ischemia. Our objective was to investigate the correlation of noncontrast CT (NCCT) ASPECTS and CTA-SI ASPECTS with CTP core volumes. Methods: We utilized a single institutional, retrospective registry of consecutive patients with acute ischemic stroke with large vessel occlusion between May 2016 and May 2018. We graded ASPECTS both on baseline NCCT and CTA-SI and measured CTP core using automated RAPID software (cerebral blood flow <30%). We used Spearman’s correlation coefficients to evaluate the correlation between continuous variables. Results: A total of 52 patients fit the inclusion criteria of large vessel occlusion in 6 to 24 hours and baseline imaging work up of NCCT, CTA, and CTP. The median age was 63 (interquartile range=53.5–75) and 38.46% were female. The median NCCT ASPECTS was 7 (interquartile range=6–9), CTA-SI ASPECTS was 5 (interquartile range=4–7), and CTP core was 14.5 mL (interquartile range=0–46 mL). There was a moderate correlation between NCCT ASPECTS and CTP core (r s =−0.55, P <0.0001) and between CTA-SI ASPECTS and CTP core (r s =−0.50, P =0.0002). The optimal NCCT ASPECTS cutoff score to detect CTP core ≤70 mL was ≥6 (sensitivity, 0.84; specificity, 0.57; positive predictive value, 0.93; negative predictive value, 0.36) and the optimal CTA-SI ASPECTS was ≥5 (sensitivity, 0.76; specificity, 0.71; positive predictive value, 0.94; negative predictive value, 0.31). Conclusions: There was a moderate correlation between NCCT and CTA-SI ASPECTS in predicting CTP defined ischemic core in delayed time windows. Further studies are needed to determine if NCCT and CTA imaging could be used for image-based patient selection when CTP imaging is not available.

scholarly journals Deep Learning Based Software to Identify Large Vessel Occlusion on Noncontrast Computed Tomography

Stroke ◽  
2020 ◽  
Vol 51 (10) ◽  
pp. 3133-3137
Author(s):  
Marta Olive-Gadea ◽  
Carlos Crespo ◽  
Cristina Granes ◽  
Maria Hernandez-Perez ◽  
Natalia Pérez de la Ossa ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Deep Learning ◽  
Positive Predictive Value ◽  
Acute Stroke ◽  
Negative Predictive Value ◽  
Predictive Value ◽  
Learning Algorithm ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
Noncontrast Computed Tomography

Background and Purpose: Reliable recognition of large vessel occlusion (LVO) on noncontrast computed tomography (NCCT) may accelerate identification of endovascular treatment candidates. We aim to validate a machine learning algorithm (MethinksLVO) to identify LVO on NCCT. Methods: Patients with suspected acute stroke who underwent NCCT and computed tomography angiography (CTA) were included. Software detection of LVO (MethinksLVO) on NCCT was tested against the CTA readings of 2 experienced radiologists (NR-CTA). We used a deep learning algorithm to identify clot signs on NCCT. The software image output trained a binary classifier to determine LVO on NCCT. We studied software accuracy when adding National Institutes of Health Stroke Scale and time from onset to the model (MethinksLVO+). Results: From 1453 patients, 823 (57%) had LVO by NR-CTA. The area under the curve for the identification of LVO with MethinksLVO was 0.87 (sensitivity: 83%, specificity: 71%, positive predictive value: 79%, negative predictive value: 76%) and improved to 0.91 with MethinksLVO+ (sensitivity: 83%, specificity: 85%, positive predictive value: 88%, negative predictive value: 79%). Conclusions: In patients with suspected acute stroke, MethinksLVO software can rapidly and reliably predict LVO. MethinksLVO could reduce the need to perform CTA, generate alarms, and increase the efficiency of patient transfers in stroke networks.

scholarly journals Utility of Leptomeningeal Collaterals in Predicting Intracranial Atherosclerosis-Related Large Vessel Occlusion in Endovascular Treatment

2020 ◽  
Vol 9 (9) ◽  
pp. 2784 ◽  
Author(s):  
Jang-Hyun Baek ◽  
Byung Moon Kim ◽  
Jin Woo Kim ◽  
Dong Joon Kim ◽  
Ji Hoe Heo ◽  
...  
Keyword(s):  
Endovascular Treatment ◽  
Negative Predictive Value ◽  
Predictive Value ◽  
Area Under The Curve ◽  
Large Vessel ◽  
Intracranial Atherosclerosis ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
High Negative Predictive Value ◽  
Independent Association

Earlier or preprocedural identification of occlusion pathomechanism is crucial for effective endovascular treatment. As leptomeningeal collaterals tend to develop well in chronic ischemic conditions such as intracranial atherosclerosis (ICAS), we investigated whether leptomeningeal collaterals can be a preprocedural marker of ICAS-related large vessel occlusion (ICAS-LVO) in endovascular treatment. A total of 226 patients who underwent endovascular treatment were retrospectively reviewed. We compared the pattern of leptomeningeal collaterals between patients with ICAS-LVO and without. Leptomeningeal collaterals were assessed by preprocedural computed tomography angiography (CTA) and basically categorized by three different collateral assessment methods. Better leptomeningeal collaterals were significantly associated with ICAS-LVO, although they were not independent for ICAS-LVO. When leptomeningeal collaterals were dichotomized to incomplete (<100%) and complete (100%), the latter was significantly more frequent in patients with ICAS-LVO (52.5% versus 20.4%) and remained an independent factor for ICAS-LVO (odds ratio, 3.32; 95% confidence interval, 1.52–7.26; p = 0.003). The area under the curve (AUC) value of complete leptomeningeal collateral supply was 0.660 for discrimination of ICAS-LVO. Incomplete leptomeningeal collateral supply was not likely ICAS-LVO, based on the high negative predictive value (88.6%). Considering its negative predictive value and the independent association between complete leptomeningeal collateral supply and ICAS-LVO, leptomeningeal collaterals could be helpful in the preprocedural determination of occlusion pathomechanism.

scholarly journals Paramedic utilization of Vision, Aphasia, Neglect (VAN) stroke severity scale in the prehospital setting predicts emergent large vessel occlusion stroke

2020 ◽  
pp. neurintsurg-2020-016054 ◽  
Author(s):  
Lee Birnbaum ◽  
David Wampler ◽  
Arash Shadman ◽  
Mateja de Leonni Stanonik ◽  
Michele Patterson ◽  
...  
Keyword(s):  
Predictive Value ◽  
Systems Of Care ◽  
Prehospital Setting ◽  
Large Vessel ◽  
Stroke Severity ◽  
Large Vessel Occlusion ◽  
Intraparenchymal Hemorrhage ◽  
Vessel Occlusion ◽  
Statistical Measures ◽  
Published Evidence

BackgroundNumerous stroke severity scales have been published, but few have been studied with emergency medical services (EMS) in the prehospital setting. We studied the Vision, Aphasia, Neglect (VAN) stroke assessment scale in the prehospital setting for its simplicity to both teach and perform. This prospective prehospital cohort study was designed to validate the use and efficacy of VAN within our stroke systems of care, which includes multiple comprehensive stroke centers (CSCs) and EMS agencies.MethodsThe performances of VAN and the National Institutes of Health Stroke Scale (NIHSS) ≥6 for the presence of both emergent large vessel occlusion (ELVO) alone and ELVO or any intracranial hemorrhage (ICH) combined were reported with positive predictive value, sensitivity, negative predictive value, specificity, and overall accuracy. For subjects with intraparenchymal hemorrhage, volume was calculated based on the ABC/2 formula and the presence of intraventricular hemorrhage was recorded.ResultsBoth VAN and NIHSS ≥6 were significantly associated with ELVO alone and with ELVO or any ICH combined using χ2 analysis. Overall, hospital NIHSS ≥6 performed better than prehospital VAN based on statistical measures. Of the 34 cases of intraparenchymal hemorrhage, mean±SD hemorrhage volumes were 2.5±4.0 mL for the five VAN-negative cases and 17.5±14.2 mL for the 29 VAN-positive cases.ConclusionsOur VAN study adds to the published evidence that prehospital EMS scales can be effectively taught and implemented in stroke systems with multiple EMS agencies and CSCs. In addition to ELVO, prehospital scales such as VAN may also serve as an effective ICH bypass tool.

scholarly journals Stroke vision, aphasia, neglect (VAN) assessment—a novel emergent large vessel occlusion screening tool: pilot study and comparison with current clinical severity indices

2016 ◽  
Vol 9 (2) ◽  
pp. 122-126 ◽  
Author(s):  
Mohamed S Teleb ◽  
Anna Ver Hage ◽  
Jaqueline Carter ◽  
Mahesh V Jayaraman ◽  
Ryan A McTaggart
Keyword(s):  
Pilot Study ◽  
Positive Predictive Value ◽  
Predictive Value ◽  
Screening Tool ◽  
Clinical Severity ◽  
Screening Tools ◽  
Large Vessel ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
Nihss Score

BackgroundIdentification of emergent large vessel occlusion (ELVO) stroke has become increasingly important with the recent publications of favorable acute stroke thrombectomy trials. Multiple screening tools exist but the length of the examination and the false positive rate range from good to adequate. A screening tool was designed and tested in the emergency department using nurse responders without a scoring system.MethodsThe vision, aphasia, and neglect (VAN) screening tool was designed to quickly assess functional neurovascular anatomy. While objective, there is no need to calculate or score with VAN. After training participating nurses to use it, VAN was used as an ELVO screen for all stroke patients on arrival to our emergency room before physician evaluation and CT scan.ResultsThere were 62 consecutive code stroke activations during the pilot study. 19 (31%) of the patients were VAN positive and 24 (39%) had a National Institutes of Health Stroke Scale (NIHSS) score of ≥6. All 14 patients with ELVO were either VAN positive or assigned a NIHSS score ≥6. While both clinical severity thresholds had 100% sensitivity, VAN was more specific (90% vs 74% for NIHSS ≥6). Similarly, while VAN and NIHSS ≥6 had 100% negative predictive value, VAN had a 74% positive predictive value while NIHSS ≥6 had only a 58% positive predictive value.ConclusionsThe VAN screening tool accurately identified ELVO patients and outperformed a NIHSS ≥6 severity threshold and may best allow clinical teams to expedite care and mobilize resources for ELVO patients. A larger study to both validate this screening tool and compare with others is warranted.

Positive predictive value and stroke workflow outcomes using automated vessel density (RAPID-CTA) in stroke patients: One year experience

2021 ◽  
pp. 197140092110123
Author(s):  
Julie Adhya ◽  
Charles Li ◽  
Laura Eisenmenger ◽  
Russell Cerejo ◽  
Ashis Tayal ◽  
...  
Keyword(s):  
Positive Predictive Value ◽  
Predictive Value ◽  
Vessel Density ◽  
Large Vessel ◽  
High Grade ◽  
Modified Rankin Scale ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
One Year ◽  
Density Threshold

Purpose Several new techniques have emerged for detecting anterior circulation large vessel occlusion by quantifying relative vessel density including RAPID-CTA, potentially allowing for faster triage and decreased time to mechanical thrombectomy. We present our one-year experience on positive predictive value of RAPID-CTA for the detection of large vessel occlusion in patients presenting with stroke symptoms and its effect on treatment time and clinical outcomes. Materials and methods Three hundred and ten patients presenting with stroke symptoms with relative vessel density <60% on RAPID-CTA were included (average age 70 years, 145 male, 165 female). Examinations were considered positive if there was evidence of large vessel occlusion or high grade stenosis. Computed tomography angiography to groin puncture time was calculated during one-year time intervals before and after RAPID-CTA installation. Ninety-day Modified Rankin Scale scores were obtained for patients in each cohort. Results Of the 310 patients, 270 had large vessel occlusion or high grade stenosis (87% positive predictive value), with 161 having large vessel occlusion. Using 45% relative vessel density threshold, 129/161 large vessel occlusion were detected (80% sensitivity) and 163/172 examinations were positive (95% positive predictive value). Computed tomography angiography to groin puncture time was significantly lower after deployment of RAPID-CTA (93 min vs 68 min, p<0.05). Average 90 day modified Rankin Scale score was lower in the RAPID-CTA group with a higher percentage of patients with functional independence, although the data was not statistically significant. Conclusion RAPID-CTA had high positive predictive value for large vessel occlusion with a 45% relative vessel density threshold, which could facilitate active worklist reprioritization. Time to treatment was significantly lower and clinical outcomes were improved after deployment of RAPID-CTA.

Abstract 1122‐000108: AI‐Software Detection of Large Vessel Occlusion Stroke on CTA: Real‐World Diagnostic Test Accuracy Study

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Stavros Matsoukas ◽  
Jacob Morrey ◽  
Gregory Lock ◽  
Deeksha Chada ◽  
Tomoyoshi Shigematsu ◽  
...  
Keyword(s):  
Negative Predictive Value ◽  
Real World ◽  
Predictive Value ◽  
Area Under The Curve ◽  
Large Vessel ◽  
Test Accuracy ◽  
Index Test ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
Actual Performance

Introduction : The treatment for large vessel occlusion (LVO) stroke has significantly improved in recent years with the advent of endovascular therapy (EVT). The triage of LVOs requires rapid completion, interpretation, and communication of neuroimaging. Historically, these steps were performed manually, potentially leading to treatment delays. A computer‐aided triage software, Viz LVO, streamlines this process by providing a(n) image viewer, communication system, and artificial intelligence‐based algorithm that automatically detects LVOs and alerts appropriate teams. However, the actual performance is yet to be determined. We sought to determine the real‐world accuracy of Viz LVO in a large, tiered hub and spoke healthcare network. Methods : All consecutive head and neck computed tomography angiography (CTA) scans that were performed in the context of stroke codes and read by Viz LVO during the period of May 2019 to October 2020 were included. CTA impressions provided by radiologists served as the clinical reference standard test and Viz output served as the index test. Results : Of the 5,381 stroke codes, 1,822 had a CTA read by Viz LVO and were analyzed. Impression was negative for occlusion in 1,632 CTAs. Of the 190 occlusions, only 142 were ICA‐T, M1, or M2 and constituted the LVO population of our study. Accuracy metrics were analyzed for two different subgroups. For the ICA‐T, M1, and M2 subgroup, the algorithm yielded 74.6% sensitivity, 91.1% specificity, 97.6% negative predictive value, 89.8% accuracy and 0.86 area under the curve. Excluding M2 for the analysis, the accuracy metrics were 93.8%, 91.1%, 99.7%, 91.2% and 0.95, respectively. Sensitivity for ICA‐T, M1, and M2 occlusions was 100%, 93%, and 49%, respectively. Importantly, the algorithm has better sensitivity for proximal M2 occlusions (58%) compared to mid/distal M2 occlusions (28%), P<0.03. Conclusions : High sensitivity and negative predictive value allows Viz LVO to be a powerful adjunct tool in stroke diagnostics. The fast and accurate diagnosis can potentially save time and help identify difficult cases in the clinical setting.

Abstract TP240: The PLUMBER (Prevalence of Large Vessel Occlusion Stroke in Mecklenburg County Emergency Response) Study

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Adeline R Dozois ◽  
Lorrie Hampton ◽  
Carlene W Kingston ◽  
Gwen Lambert ◽  
Thomas J Porcelli ◽  
...  
Keyword(s):  
Acute Stroke ◽  
Emergency Response ◽  
Predictive Value ◽  
Large Vessel ◽  
Stroke Severity ◽  
Large Vessel Occlusion ◽  
Vessel Occlusion ◽  
Mecklenburg County ◽  
Ischemic Attack ◽  
Neurovascular Imaging

Introduction: Regional Emergency Medical System (EMS) protocols for acute stroke endorse routing patients with possible large vessel occlusion (LVO) acute ischemic strokes (AIS) directly to endovascular centers. These routing algorithms include prehospital stroke severity screens (PSSS) to determine the likelihood of an LVO AIS. An essential, but unreported, determinant of the predictive value of PSSS tools is the prevalence of LVO AIS stroke in the EMS population screened for stroke. Hypothesis: Among EMS patients transported to Mecklenburg county hospitals screened for stroke, acute LVO AIS prevalence ranges from 5-10%. Methods: We are conducting a prospective, observational study of all patients transported by the Mecklenburg county EMS agency who are either (1) dispatched as a possible stroke and/or (2) with a primary impression of stroke recorded by prehospital providers. We are reviewing medical records and neurovascular imaging studies to determine an acute LVO AIS diagnosis and the site(s) of occlusion. Results: Thus far, over a six-month period we have enrolled 1441 patients, of whom 33% (n=480) had a diagnosis consistent with acute stroke (ischemic stroke, hemorrhagic stroke, or transient ischemic attack), with 20% (n=287) being an AIS. Eighty-eight percent (n=253) of AIS patients underwent an intracranial CTA or MRA. The prevalence of LVO stroke in the EMS population enrolled was 5.7% (n= 82, 95% CI 4.6-7.0%), with the most common vessel occluded being M1 (n=46, 56% of LVO AIS). The prevalence of LVO AIS in patients dispatched as a possible stroke was 4.8% (n =56; 95% CI 3.6-6.1%), while the prevalence in patients with a primary impression of stroke was 10% (n=74; 95% CI 8.2-13%). Conclusions: Among patients screened for stroke by our county’s EMS agency, the prevalence of LVO AIS is low. This low LVO AIS prevalence, combined with a PSSS tool with modest accuracy, will yield poor predictive value for LVO AIS in an EMS population, resulting in a substantial rate of over-triage of non-LVO patients to endovascular centers. Data collection is ongoing to determine the accuracy of a prehospital stroke screen in identifying LVO AIS patients.

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