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How accurate are prehospital prediction scales for large anterior vessel occlusion?

JAMA Neurology
Reuters Health - 02/12/2020 - A comparison of seven prediction scales for symptomatic large anterior vessel occlusion (sLAVO) found that all had good accuracy, high specificity and low sensitivity, although two scored highest.

"The passing of time between stroke onset and starting endovascular thrombectomy (EVT) is the most important factor limiting clinical efficacy," Dr. Nyika Kruyt of Leiden University Medical Center told Reuters Health by email. "Taking into account that after a work-up in a primary stroke center, transferring a patient to a comprehensive stroke center takes about 60 minutes, it is of paramount importance to triage these patients in the ambulance to allocate them to a comprehensive stroke center immediately."

As reported in JAMA Neurology, the study was conducted from July 2018-October 2019 in an urban center in the Netherlands with a population of approximately two million people, and included two emergency medical services (EMSs), three comprehensive stroke centers (CSAs) and four primary stroke centers (PSCs).

The analysis included 2,007 patients (mean age, 71; 51%, men; median NIHSS score, 4) who received acute stroke codes with clinical observations filled in by EMS paramedics; 7.9% had sLAVO. Dr. Kruyt and colleagues used the data to assess the accuracy and feasibility of seven prediction scales: Los Angeles Motor Scale (LAMS); Rapid Arterial Occlusion Evaluation (RACE); Cincinnati Stroke Triage Assessment Tool; Prehospital Acute Stroke Severity (PASS); gaze-face-arm-speech-time; Field Assessment Stroke Triage for Emergency Destination; and gaze, facial asymmetry, level of consciousness, extinction/inattention.

Median symptom-onset-to door time was shorter in patients with sLAVO vs without sLAVO (115 vs. 142 minutes). More patients with than without sLAVO received intravenous thrombolysis (IVT; 38.6% vs. 13.7%).

Endovascular thrombectomy was done in 100 patients with sLAVO (63.3%), with a median door-to-groin-puncture time of 72 minutes. The median door-to-groin-puncture time was shorter for patients who presented directly to a CSC (61 minutes) than for those who first presented in a PSC (114 minutes).

Scale accuracy ranged from 0.79 to 0.89, with LAMS and RACE scales yielding the highest scores.

Specificity was high for all scales (range, 80%-93%), but sensitivity was low (38%-62%). Scale feasibility rates ranged from 78% to 88%, with the highest rate for the PASS scale.

The authors note, "Applying LAMS to our cohort, an urban region with relatively short distances between PSCs and CSCs and a low prevalence of sLAVO, indicated that 13 patients with sLAVO who first presented to a PSC would have benefited from direct allocation to a CSC, 17 patients with ischemic stroke treated with IVT allocated to a PSC would have unnecessarily bypassed a PSC, and 38 patients without sLAVO (including stroke mimics) allocated to a PSC would have been allocated to a CSC."

Dr. Kruyt said the results can be extrapolated to the U.S. and other regions because the rates of sLAVO and other outcomes are similar to rates reported elsewhere.

"Of interest," he noted, "EMS workers did not receive focused training before the study commenced and therefore the feasibility of the scales of about 70-80% will likely be the same elsewhere, since in most regions the protocols for stroke code patients are similar. We do think that with focused training, assessment of some clinical scales items can be improved - for example assessment of neglect and motor function."

Dr. Kori Zachrison of Massachusetts General Hospital and Harvard Medical School, coauthor of a related editorial, said the study is "very important (and) advances the science."

"The process of prehospital triage in stroke systems of care is really complex and also very dependent on local and regional circumstances," he commented in an email to Reuters Health. "At the same time, optimizing prehospital stroke triage entails more than simply choosing the best prehospital stroke scale. There are many other critical factors in the equation, for example, understanding local geography, available hospitals options in an area and their stroke-related resources."

"Thoughtfully organizing our stroke systems depends on so many of these things, and one critical piece is having an understanding of test characteristics of the prehospital stroke scales that (the authors) provide," he concluded.

SOURCE: https://bit.ly/2Vrkkxh and https://bit.ly/3g90W1S JAMA Neurology, online November 30, 2020.

By Marilynn Larkin

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