Results Summary

What was the research about?

A stroke happens when blood clots block blood supply to the brain. Strokes can cause disability or death. If patients receive treatment with medicine quickly, they may have a better recovery.

In this study, the research team compared two approaches to treat patients suspected of having a stroke who called 911:

  • Mobile stroke units, or MSUs. MSUs are ambulances with special equipment and staff who can diagnose and treat stroke. MSU staff evaluated each patient when the MSU ambulance arrived to answer the 911 call. If the patient had had a stroke, MSU staff took blood samples and x-rays to see if the patient could receive medicine to break up blood clots. MSU staff gave medicine to the patient in the ambulance, then took them to a stroke center emergency room, or ER. The MSU staff included paramedics, nurses, and an x-ray technician.
  • Standard ER care. Paramedics picked up the patient in an ambulance. They asked the patient about their medical history, checked their blood sugar, and took them to a stroke center ER. Staff at the ER took blood samples and x-rays to see if the patient could receive medicine to break up blood clots. ER staff gave medicine to the patient based on their test results.

What were the results?

Three months after a stroke, compared with standard ER care, patients treated in an MSU were more likely to recover from the stroke without disability. Also, patients treated in an MSU received medicine to treat the stroke 36 minutes sooner, on average, than those receiving standard ER care.

The two approaches didn’t differ in patient quality of life, survival, or healthcare use.

Who was in the study?

The study included 1,047 patients ages 18 and older treated for stroke in one of seven cities across the United States. Of these patients, 54 percent were White, 39 percent were Black, 4 percent were Asian, and 3 percent were another race or didn’t report a race; 17 percent were Hispanic or Latino. The average age was 66, and 51 percent were women.

What did the research team do?

The research team worked with emergency medical services (EMS) to provide care for patients who might have had a stroke. From August 2014 until August 2020, the response to 911 calls for these patients switched each week between the two approaches to treat stroke.

The research team interviewed patients and caregivers about the patient’s level of disability three months after their stroke. Patients and caregivers completed surveys about the patient’s quality of life and healthcare use at the start of the study and every three months for one year after their stroke.

Patients with a history of stroke and EMS staff helped design the study.

What were the limits of the study?

The study took place in seven cities. Results may differ in rural areas.

Future research could compare MSUs and standard ER care in rural areas.

How can people use the results?

Health systems can use the results when considering ways to treat patients who have had a stroke.

Final Research Report

This project's final research report is expected to be available by September 2024.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments.

Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:

  • The reviewers questioned how the researchers established the treatment groups for analysis. In the study, the standard management (SM) and mobile stroke unit (MSU) interventions were delivered on alternate days or weeks so that each intervention condition would include the same number of patients. However, the report states that 35 people assigned to the MSU intervention actually received SM intervention. Therefore, these 35 people were included in the SM group for the primary analyses, but in the MSU group for sensitivity analyses. The researchers explained that sometimes on MSU weeks the mobile van was not available, so some people received standard care and were counted in the SM group to help with recruitment numbers. The researchers assured the reviewers that these group assignment changes did not create added bias in the analyses.
  • The reviewers noted that the better stroke outcomes for the MSU group over the SM group might not be because treatment with an intravenously administered thrombolytic occurred sooner. Another reason for this difference between groups could be attributed to more accurate treatment administration by MSU personnel, who were specially trained in the procedure, than by the SM personnel, who handled all manner of medical emergencies. The researchers agreed that speed and accuracy were factors in the better outcomes for patients treated by the MSU than for patients in SM.
  • The reviewers asked about the clusters created by the timed administration of MSU and SM because differences between the groups could be accounted for by weekly clusters for treatment. The reviewers recommended that the researchers consider adding a variable to account for clustering to their analyses to account for this possible effect, but the researchers explained that they did not have the week cluster information in their database so they could not conduct additional analyses. The researchers did add this concern to their study limitations.

Conflict of Interest Disclosures

Project Information

James Grotta, MD
Memorial Hermann-Texas Medical Center
BEnefits of Stroke Treatment Delivered Using a Mobile Stroke Unit Compared to Standard Management by Emergency Medical Services: The BEST-MSU Study

Key Dates

July 2016
August 2023

Study Registration Information


Has Results
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Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Populations Populations PCORI is interested in research that seeks to better understand how different clinical and health system options work for different people. These populations are frequently studied in our portfolio or identified as being of interest by our stakeholders. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
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Last updated: January 24, 2024