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Martin Gude,1 Hans Kirkegaard,1,2 Rolf Blauenfeldt,3 Anne Behrndtz,3 Jeppe Mainz,3 Ingunn Riddervold,4 Claus Z Simonsen,2,3 Niels Hjort,2,3 Søren P Johnsen,5 Grethe Andersen,2,3 Jan Brink Valentin5 1Department of Research and Development, Prehospital Emergency Medical Services, Central Denmark Region; and Aarhus University Hospital, Aarhus, Denmark; 2Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; 3Danish Stroke Center, Department of Neurology, Aarhus University Hospital, Aarhus, Denmark; 4Norwegian Air Ambulance Foundation, Oslo, Norway; 5Danish Center for Clinical Health Services Research, Department of Clinical Medicine, Aalborg University, Aalborg, DenmarkCorrespondence: Martin Gude, Prehospital Emergency Medical Services, Central Denmark Region and Aarhus University Hospital, Aarhus, Denmark, Email gude@dadlnet.dkObjective: To examine the agreement between emergency medical service (EMS) providers, neurology residents and neurology consultants, using the Cincinnati Prehospital Stroke Scale (CPSS) and the Prehospital Acute Stroke Severity Scale (PASS).Methods: Patients with stroke, transient ischemic attack (TIA) and stroke mimic were included upon primary stroke admission or during rehabilitation. Patients were included from June 2018 to September 2019. Video recordings were made of patients being assessed with CPSS and PASS. The recordings were later presented to the healthcare professionals. To determine relative and absolute interrater reliability in terms of inter-rater agreement (IRA), we used generalisability theory. Group-level agreement was determined against a gold standard and presented as an area under the curve (AUC). The gold standard was a consensus agreement between two neurology consultants.Results: A total of 120 patient recordings were assessed by 30 EMS providers, two neurology residents and two neurology consultants. Using the CPSS and the PASS, a total of 1,800 assessments were completed by EMS providers, 240 by neurology residents and 240 by neurology consultants. The overall relative and absolute IRA for all items combined from the CPSS and PASS score was 0.84 (95% CI 0.80; 0.87) and 0.81 (95% CI 0.77; 0.85), respectively. Using the CPSS, the agreement on a group-level resulted in AUCs of 0.83 (95% CI 0.78; 0.88) for the EMS providers and 0.86 (95% CI 0.82; 0.90) for the neurology residents when compared with the gold standard. Using the PASS, the AUC was 0.82 (95% CI 0.77; 0.87) for the EMS providers and 0.88 (95% CI 0.84; 0.93) for the neurology residents.Conclusion: The high relative and absolute inter-rater agreement underpins a high robustness/generalisability of the two scales. A high agreement exists across individual raters and different groups of healthcare professionals supporting widespread applicability of the stroke scales.Plain Language Summary: Early stroke identification is pivotal to enable faster treatment. To aid this identification, many symptom-based stroke scales have been constructed for both stroke screening and severity assessment. In the prehospital environment, several scales have been evaluated on performance, but only few studies have evaluated the agreement between the ambulance personnel (emergency medical service (EMS) providers) and stroke physicians when interpreting the assessed symptoms in the scales. It is of great importance to know how EMS providers interpret symptoms seen in connection with the use of the scales to focus the continuous training of the EMS providers but also to aid the decision on which scale to implement in ambulances. From previous studies, we know that complex stroke scales are used to a considerably lesser extent than more simple scales, which could be caused by difficulties interpreting specific symptoms. In this study, a variety of methods was applied to determine the inter-rater agreement for two simple stroke scales using dichotomously evaluated symptoms. High inter-rater agreement between EMS providers and Stroke Neurologists exists both between individual raters and between raters grouped according to their profession and seniority. Previous studies have also found high inter-rater agreement for simple stroke scales but lesser agreement for more advanced scales. In conclusion, simple stroke scales seem to produce the highest agreement.Keywords: observer variation, prehospital emergency care, emergency medical service provider, neurologists, stroke