Richard Jackson, MD
Kentaro Suzuki et al. developed a new prehospital stroke scale called the Emergent Large Vessel Occlusion (ELVO) screen for use by paramedics to identify large vessel occlusions (LVO) for diversion of transport to the nearest thrombectomy-capable location.
In the introduction, they comment that transport of patients without LVO is “unwise, time consuming, and expensive” and, therefore, the need has arisen for better emergent stroke transportation systems. They base this on data that showed, in their words, unacceptable negative predictive values (NPV) and a possible 20% of missed LVO eligibility.
They comprised their scale based on cortical symptoms with simplicity in mind. The scale consists of paramedic observation of eye deviation, a question regarding naming of eye glasses or a watch, and a question about neglect regarding naming of the number of fingers being held up for visual confrontation. A positive result was an abnormality on any of the three items.
The scale was tested from September 2016 to July 2017 in four stroke centers in Japan. Paramedics were asked to apply the scale when there was a call ahead for transport of a patient. Baseline characteristics, diagnosis on admission, and presence of LVO documented by magnetic resonance angiography were recorded prospectively. LVO was defined as an occlusion of the internal carotid, M1 MCA, insular M2, basilar, or P1 PCA segments. 413 patients were enrolled with 227 at a single site. 271 were diagnosed with an ischemic stroke (66%). The other diagnoses were ICH (18%), SAH (2%), and other (15%). LVO was diagnosed in 114 patients (28%). Sensitivity and specificity for detecting LVO were found to be 85% and 72%. Positive predictive value was 54%, and negative predictive value was 93%. Accuracy of diagnosis was found to be 76%.
The conclusion was that this scale had corrected the previous loss of NPV by focusing on cortical signs. They compare this to the 3-item scale, Los Angeles Motor Scale, Cincinnati Prehospital Stroke Severity scale, Prehospital Acute Stroke Severity scale, and Field Assessment Stroke Triage for Emergency Destination scales acknowledging that the Rapid Arterial Occlusion Evaluation scale has comparable effectiveness.
They comment that ELVO is simpler and easier to use. While a higher NPV has been corrected in this scale, the focus here is very simply to not miss a chance to intervene on an LVO. However, it has not clearly been demonstrated yet that bypassing IV-tPA at a primary stroke center and going straight to thrombectomy is more beneficial than the more traditional route of IV-tPA evaluation before thrombectomy. In areas of the country where there is a high density of thrombectomy-capable centers, this type of triage may be appropriate. However, in the U.S., there are many areas where there is still a single thrombectomy-capable center with many surrounding primary stroke centers. Consideration for overloading the comprehensive center system with a sensitivity of PPV of 54% is no small consideration given that the burden of this new volume will be almost 50% stroke mimic or other non-thrombectomy-eligible diagnosis. As someone who works in both a primary and a comprehensive stroke center, this seems to be a step in the right direction, but not the final answer.
