Field Assessment Stroke Triage for Emergency Destination: A Simple and Accurate Prehospital Scale to Detect Large Vessel Occlusion Strokes

Abstract

Background and purpose: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: cerebrovascular occlusion; scale; stroke, acute, prehospital emergency care; triage.

© 2016 American Heart Association, Inc.

Figures

Figure 1

* A - ROC curves comparing the discrimination of FAST-ED, NIHSS, RACE and CPSS scales for the detection of LVOS (all subjects); B – Subjects who performed CTA ≤ 12 hours from symptom onset; C – Subjects who performed CTA ≤ 6 hours from symptom onset. * all individual curves presented a p value

Figure 2

Proportion of patients with LVOS according to the FAST-ED scale*. *Hosmer and Lemeshow test: 0.62

Figure 3

Proportion of patients with LVOS according to the FAST-ED scale and most proximal site of occlusion. Intracranial ICA MCA-M1 MCA-M2