Functional stroke outcomes after mobile stroke unit deployment - the revised protocol for the Berlin Prehospital Or Usual Delivery of acute stroke care (B_PROUD) part 2 study.

Background: Studies investigating the Mobile Stroke Unit (MSU) concept have shown increased thrombolysis rates, reduced alarm-to-treatment times and improved prehospital triage. Yet, so far, there is no definite scientific proof of better functional outcome after MSU deployment compared to regular ambulances.

Methods: We provide a revised protocol for the second part of the B_PROUD trial as organization of the MSU dispatch did not meet the anticipated standards in the first part. B_PROUD is a pragmatic, prospective study comparing functional outcomes of treatment candidates with or without MSU care. Treatment candidates are defined as patients with a final diagnosis of ischemic stroke or transient ischemic attack, onset-to-dispatch-times ≤4 h, disabling symptoms not resolved at time of ambulance arrival, and the ability to ambulate prior to the qualifying event. These patients are included if their emergency call prompted a stroke alarm at the dispatch center during MSU operation hours (7 am-11 pm, Monday-Sunday) and if the emergency is located within the MSU operation area in Berlin, Germany. The intervention group consists of patients who are cared for by the MSU. When the MSU is already in operation for another emergency, MSU dispatches are handled by regular ambulances (about 45%). These dispatches create the control group. Blinded stroke physicians assess the modified Rankin Scale (mRS) score in recorded structured interviews 3 months after stroke. The primary outcome is the degree of disability and death over the full range of the mRS. As a change to the previously published protocol and only pertinent in case of more than 9% lost-to-follow-up, a co-primary outcome was introduced consisting of the proportions of death, new institutional care or severe disability in patients with additional use of information from registration offices.

Perspective: The results will inform parties involved in acute stroke care organization on the effectiveness of the MSU concept.

Trial Registration: The protocol is registered in (NCT03931616) and has been approved by the ethical review committee of the Charité - University Medicine Berlin (EA4/109/15) on September 2, 2015. The study protocol of B_PROUD part 1 had been published in the International Journal of Stroke as "Berlin Prehospital Or Usual Delivery of acute stroke care (B_PROUD) - study protocol" (doi: 10.1177/1747493017700152) on March 22, 2017 [1] previous to first patient's registration.