Utility of Severity-Based Prehospital Triage for Endovascular Thrombectomy: ACT-FAST Validation Study

Henry Zhao; Karen Smith; Stephen Bernard; Michael Stephenson; Henry Ma; Ronil V Chandra; Thanh Phan; Christopher F Bladin; Leonid Churilov; Douglas Crompton; Helen M Dewey; Tissa Wijeratne; Geoffrey Cloud; Vincent Thijs; Timothy J Kleinig; Jo Lyn Ng; Cameron Williams; Fana Alemseged; Felix Ng; Peter J Mitchell; Mark W Parsons; Nawaf Yassi; Stephen M Davis; Bruce C V Campbell

doi:10.1161/STROKEAHA.120.031467

Utility of Severity-Based Prehospital Triage for Endovascular Thrombectomy: ACT-FAST Validation Study

Stroke. 2021 Jan;52(1):70-79. doi: 10.1161/STROKEAHA.120.031467. Epub 2020 Dec 22.

Authors

Henry Zhao^{1

2}, Karen Smith^{1

3

4}, Stephen Bernard^{1

4}, Michael Stephenson², Henry Ma⁵, Ronil V Chandra⁵, Thanh Phan⁵, Christopher F Bladin^{2

6}, Leonid Churilov^{1

7}, Douglas Crompton⁸, Helen M Dewey⁶, Tissa Wijeratne⁹, Geoffrey Cloud¹⁰, Vincent Thijs¹¹, Timothy J Kleinig¹², Jo Lyn Ng¹, Cameron Williams¹, Fana Alemseged¹, Felix Ng^{1

8

2

11}, Peter J Mitchell^{1

13}, Mark W Parsons¹, Nawaf Yassi^{1

2

4

14}, Stephen M Davis¹, Bruce C V Campbell^{1

2}

Affiliations

¹ Departments of Medicine and Neurology, Melbourne Brain Centre at The Royal Melbourne Hospital (H.Z., L.C., J.L.N., C.W., F.A., F.N., P.J.M., M.W.P., N.Y., S.M.D., B.C.V.C.), University of Melbourne, Australia.
² Ambulance Victoria, Melbourne, Australia (H.Z., K.S., S.B., M.S., C.F.B., F.N., N.Y., B.C.V.C.).
³ Department of Epidemiology and Preventive Medicine, Department of Community Emergency Health and Paramedic Practice (K.S.), Monash University, Melbourne, Australia.
⁴ Discipline of Emergency Medicine, University of Western Australia (K.S., S.B.).
⁵ Monash Health and Department of Medicine, School of Clinical Science (H.M., R.V.C., T.P.), Monash University, Melbourne, Australia.
⁶ Department of Neurology, Eastern Health and Eastern Health Clinical School, Faculty of Medicine, Nursing and Health Sciences (C.F.B., H.M.D.), Monash University, Melbourne, Australia.
⁷ Department of Medicine, Austin Health, Melbourne Medical School (L.C.), University of Melbourne, Australia.
⁸ Department of Neurology, Northern Health, Faculty of Medicine, Dentistry and Health Sciences (D.C., F.N.), University of Melbourne, Australia.
⁹ Department of Neurology, Western Health, Faculty of Medicine, Dentistry and Health Sciences (T.W.), University of Melbourne, Australia.
¹⁰ Department of Neurology, Alfred Health, Department of Clinical Neurosciences, Central Clinical School (G.C.), Monash University, Melbourne, Australia.
¹¹ Department of Neurology, Austin Health, Australia (V.T., F.N.).
¹² Department of Neurology, Royal Adelaide Hospital, Australia (T.J.K.).
¹³ Department of Radiology, Royal Melbourne Hospital (P.J.M.), University of Melbourne, Australia.
¹⁴ Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia (N.Y.).

PMID: 33349016
DOI: 10.1161/STROKEAHA.120.031467

Abstract

Background and purpose: Severity-based assessment tools may assist in prehospital triage of patients to comprehensive stroke centers (CSCs) for endovascular thrombectomy (EVT), but criticisms regarding diagnostic inaccuracy have not been adequately addressed. This study aimed to quantify the benefits and disadvantages of severity-based triage in a large real-world paramedic validation of the Ambulance Clinical Triage for Acute Stroke Treatment (ACT-FAST) algorithm.

Methods: Ambulance Victoria paramedics assessed the prehospital ACT-FAST algorithm in patients with suspected stroke from November 2017 to July 2019 following an 8-minute training video. All patients were transported to the nearest stroke center as per current guidelines. ACT-FAST diagnostic accuracy was compared with hospital imaging for the presence of large vessel occlusion (LVO) and need for CSC-level care (LVO, intracranial hemorrhage, and tumor). Patient-level time saving to EVT was modeled using a validated Google Maps algorithm. Disadvantages of CSC bypass examined potential thrombolysis delays in non-LVO infarcts, proportion of patients with false-negative EVT, and CSC overburdening.

Results: Of 517 prehospital assessments, 168/517 (32.5%) were ACT-FAST positive and 132/517 (25.5%) had LVO. ACT-FAST sensitivity and specificity for LVO was 75.8% and 81.8%, respectively. Positive predictive value was 58.8% for LVO and 80.0% when intracranial hemorrhage and tumor (CSC-level care) were included. Within the metropolitan region, 29/55 (52.7%) of ACT-FAST-positive patients requiring EVT underwent a secondary interhospital transfer. Prehospital bypass with avoidance of secondary transfers was modeled to save 52 minutes (95% CI, 40.0-61.5) to EVT commencement. ACT-FAST was false-positive in 8 patients receiving thrombolysis (8.1% of 99 non-LVO infarcts) and false-negative in 4 patients with EVT requiring secondary transfer (5.4% of 74 EVT cases). CSC bypass was estimated to over-triage 1.1 patients-per-CSC-per-week in our region.

Conclusions: The overall benefits of an ACT-FAST algorithm bypass strategy in expediting EVT and avoiding secondary transfers are estimated to substantially outweigh the disadvantages of potentially delayed thrombolysis and over-triage, with only a small proportion of EVT patients missed.

Keywords: ambulance; infarction; intracranial hemorrhage; thrombectomy; triage.

Publication types

Research Support, Non-U.S. Gov't
Validation Study

MeSH terms

Algorithms*
Emergency Medical Services / methods*
Emergency Medical Technicians
Endovascular Procedures
Humans
Stroke / diagnosis*
Stroke / surgery
Thrombectomy
Time-to-Treatment
Triage / methods*