Background: Clinical efficacy of endovascular treatment (EVT) for ischemic stroke with large anterior vessel occlusion (LAVO) is strongly time dependent (time=brain). Therefore, several screening tools have been developed to streamline pre-hospital stroke triage to centres offering EVT. These tools, however, are largely unvalidated in a pre-hospital setting and have hitherto not been compared head-to-head for inter-rater reliability. In this study we aim to make this comparison in an experimental pre-hospital setting.
Methods: Practicing emergency medical service nurses reviewed films of 10 different cases of a professional actor simulating stroke (mimic) symptoms by scoring items using a web-based application. This application collected these scores to reconstruct the following previously published screening tools: the LAMS, RACE, PASS, CPSS, G-FAST and FAST-ED. Fleiss’ Kappa in R was used to determine inter-rater reliability of each tool in a binary fashion. 
Results: Each of 90 EMS nurses reviewed 3 random cases. Ten cases were excluded for technical reasons resulting in a total of 260 assessments. Kappa was highest for LAMS 0.90 (95%CI 0.83-0.97) followed by FAST-ED 0.83 (95%CI 0.60-1.00), G-FAST: 0.76 (95%CI 0.51-1.00), RACE: 0.75 (95%CI 0.45-1.00), CPSS: 0.72 (95%CI 0.55-0.90) and PASS 0.58 (95%CI 0.28-0.88). 
Conclusion: LAMS and FAST-ED showed excellent inter-rater reliability, followed by G-FAST, RACE, CPSS and PASS.
Discussion: In an experimental pre-hospital setting, a high degree of inter-rater reliability can be achieved with various LAVO screening tools. These screening tools must be validated in a real clinical setting with additional testing for predictive value of the tools for LAVO.

PRE-HOSPITAL LARGE ANTERIOR VESSEL OCCLUSION RECOGNITION; AN INTER-RATER RELIABILITY STUDY