FAST-ED scale smartphone app-based prediction of large vessel occlusion in suspected stroke by emergency medical service

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FAST-ED scale smartphone app-based prediction of large vessel occlusion in suspected stroke by emergency medical service

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Benedikt Frank, Thomas Lembeck, Nina Toppe, ...

First Published November 14, 2021 Research Article 

https://doi.org/10.1177/17562864211054962

Article information

Abstract

Background and Purpose:

Considering the highly time-dependent therapeutic effect of endovascular treatment in patients with large vessel occlusion–associated acute ischemic stroke, prehospital identification of large vessel occlusion and subsequent triage for direct transport to a comprehensive stroke center offers an intriguing option for optimizing patient pathways.

Methods:

This prospective in-field validation study included 200 patients with suspected acute ischemic stroke who were admitted by emergency medical service to a comprehensive stroke center. Ambulances were equipped with smartphones running an app-based Field Assessment Stroke Triage for Emergency Destination scale for transmission prior to admission. The primary measure was the predictive accuracy of the transmitted Field Assessment Stroke Triage for Emergency Destination for large vessel occlusion and the secondary measure the predictive accuracy for endovascular treatment.

Results:

A Field Assessment Stroke Triage for Emergency Destination ⩾4 revealed very good accuracy to detect large vessel occlusion–related acute ischemic stroke with a sensitivity of 82.4% (95% confidence interval = 65.5–93.2), specificity of 78.3% (95% confidence interval = 71.3–84.3), and an area under the curve c-statistics of 0.89 (95% confidence interval = 0.85–0.94). Field Assessment Stroke Triage for Emergency Destination ⩾4 correctly identified 84% of patients who received endovascular treatment [73.5% specificity (95% confidence interval = 66.4–79.8)] with an area under the curve c-statistics of 0.82 (95% confidence interval = 0.74–0.89). In a hypothetical triage model of an urban setting, one secondary transportation would be avoided with every fifth patient screened.

Conclusion:

A smartphone app-based stroke triage completed by emergency medical service personnel showed adequate quality for the Field Assessment Stroke Triage for Emergency Destination to identify large vessel occlusion–associated acute ischemic stroke. We demonstrate feasibility of the use of a medical messaging service in prehospital stroke care. Based on these first results, a randomized trial evaluating the clinical benefit of such a triage system in an urban setting is currently in preparation.

Clinical Trial Registration: https://clinicaltrials.gov Unique identifier: NCT04404504.

Keywords

EMS, FAST-ED, prehospital LVO thrombectomy identification, stroke, triage

Introduction

The introduction of endovascular treatment (EVT) in addition to intravenous thrombolysis (IVT) has vastly improved treatment of patients with acute ischemic stroke (AIS) caused by large vessel occlusion (LVO). However, while IVT can be applied in any hospital with specialized stroke care, EVT requires a much more complex infrastructure and mostly is limited to Comprehensive Stroke Centers (CSCs). In consideration of the highly time-dependent therapeutic effect of the reperfusion therapy in AIS,^1,2 many prehospital patient pathways still focus on transportation to the nearest stroke unit. On the contrary, patients with LVO-related AIS admitted to centers without EVT capability must be referred to CSCs after initiation of IVT by secondary interhospital transfer (drip-and-ship). This procedure is not only expensive and causes inefficient use of emergency medical service (EMS) resources, but also delays the possible use of EVT, resulting in a poorer clinical outcome.³ Therefore, prehospital identification of patients with LVO and subsequent triage for direct transport to a CSC offers an intriguing option for optimizing patient pathways. This is especially useful in urban settings, where delay to first hospital contact is negligible when bypassing a nearby non-EVT center. In this context, several clinical scores were developed to estimate LVO risk in patients with AIS in the emergency setting. Among them, the simple and short Field Assessment Stroke Triage for Emergency Destination (FAST-ED) scale yields high sensitivity by adding cortical symptoms to the regular FAST-test.⁴ Previous studies have shown superior prediction quality in comparison to other LVO recognition scores;⁵ however, in-field validation has not yet been studied. In addition, very limited experience with prehospital smartphone-assisted assessment of stroke patients by paramedic EMS personnel is available⁶ and further proof of practicability is urgently needed.⁷

In this prospective study, we performed in-field validation of the smartphone-based FAST-ED scale that was digitally transmitted by paramedic EMS personnel prior to hospital arrival. In addition, we aimed to evaluate the potential impact of prehospital triage of patients with suspected stroke.

Methods

Study setting

This was a prospective in-field validation study for an app-based prehospital stroke triage for patients with suspected acute stroke. The study included 200 consecutive patients who were admitted by EMS to the CSC of the Neurological University Hospital Essen, Germany, from March 2019 to August 2020 and met the following inclusion criteria: suspected acute stroke, age above 18 years, and a digitally transmitted FAST-ED by EMS prior to admission. Patients with confirmed onset of stroke symptoms beyond 24 h were excluded.

EMS personnel of the city of Essen, which is managed by the local fire department (Feuerwehr der Stadt Essen), was systematically trained to use an app-based FAST-ED score. In addition, all ambulances were equipped with a robust smartphone (Caterpillar, CAT S60) running a customized German version of a FAST-ED triage app and a medical messaging service (JoinTriage and Join; Allm, Inc. https://play.google.com/store/apps/details?id=net.allm.fasted&hl=en https://apps.apple.com/us/app/jointriage/id1099779970). EMS personnel used this messaging platform to digitally transmit the examination results to the hospital stroke team prior to arrival.

EMS is designed as a two-tiered system including paramedic staffed ALS-Ambulances and physician staffed response units. In suspected stroke without signs of severe respiratory distress, the EMS dispatch center protocol leads to a single ALS-Ambulance response. Thus, in majority of suspected stroke, only paramedic EMS personnel is involved.

FAST-ED is a simple scale that adds clinical symptoms predicting cortical involvement (gaze deviation, denial, neglect) to the commonly used FAST-test, which already includes the evaluation of facial palsy, arm weakness, and speech disturbances. The app-based FAST-ED scale omits the need to examine symptoms of neglect and denial, if the patient suffers from aphasia or in the absence of arm weakness. The score ranges from zero to eight points (Figure 1) and FAST-ED items as well as basic clinical information (time of symptom onset, age) are entered into the Triage App, which then automatically predicts the likelihood of LVO based on previous data.⁸ Assessment results and the estimated time of arrival are digitally transferred to our hospital via the smartphone App.

Figure 1. Flow chart of the algorithm used in JoinTriage.

The assessment of age was modified from a dichotomized (⩾80 years) to a continuous variable after analyzing the first 40 patients) and information of prior oral anticoagulation was excluded from the assessment due to the lack of validity (the respective data are presented in the result section). The implementation of these changes was completed after the inclusion of 53 patients. The sequence of the FAST-ED items itself remained unchanged.⁸ The final app display and algorithm are presented in Figure 1 and Supplemental Figure S1.

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