Abstract TMP64: In-Field Paramedic Validation of the Ambulance Clinical Triage for Acute Stroke Treatment (ACT-FAST) Algorithm for Endovascular Thrombectomy

Abstract

Background: Clinical triage for endovascular thrombectomy (EVT) is the most easily deployable solution to reduce unequal geographical access to comprehensive stroke centers, but current tools have limited prehospital validation. We present results of the ongoing paramedic validation study of Ambulance Clinical Triage For Acute Stroke Treatment (ACT-FAST), a published algorithmic severity-based triage tool utilizing only 2 examination steps designed for specificity and practicality. Methods: From July 2017, Ambulance Victoria paramedics assessed ACT-FAST (arm drift followed by speech if right arm weak, or shoulder tap for inattention if left arm weak plus screening eligibility questions) in suspected stroke patients pre-hospital in Melbourne, Australia, and in the Royal Melbourne Hospital Emergency Department. Algorithm results were validated against in-hospital CT imaging. Results: Data were available from n=196 assessments (ED n=76, pre-hospital n=120). Figure 1 shows correlation with CT imaging. Overall, ACT-FAST had 92% sensitivity for ICA/M1 occlusions with NIHSS≥6 (AHA Class 1 indication for EVT). Specificity purely for large vessel occlusion was 83% (positive predictive value 57%). Only a small proportion of distal occlusions (6/46, 13%) or patients with normal imaging (4/67, 6%) were falsely identified. When considering all patients requiring comprehensive stroke center care including neurosurgery (large vessel occlusion, hemorrhage and tumor) generated a positive predictive value for ACT-FAST of 83.3%. Discussion: Current results of the real-world ACT-FAST paramedic field validation study show high accuracy for clinical recognition of patients likely to require EVT or comprehensive stroke center care. The overall benefits of expedited thrombectomy for the majority of patients with large vessel occlusion is likely to outweigh the theoretical harms of delayed thrombolysis for a small minority of patients not requiring EVT.