Background: Mobile Stroke Units (MSUs, mobile CT ambulances) are a new platform for accelerated delivery of proven, time-dependent therapies for acute ischemic and hemorrhagic stroke, undergoing systematic evaluation to determine cost-effectiveness. Formal analysis of the reach of MSU programs in the US during the early pilot period has not previously been undertaken.
Methods: We identified all US MSU programs, active or expected to be active by the end of 2017, via the PRESTO consortium, program leader referrals, vehicle and scanner manufacturer informants, and press release search. MSU access was calculated using geospatial mapping of each vehicle and its surrounding 10 mile radius catchment area, for: 1) population aged ≥ 65, using US Census Bureau county-level values for land area, population density, and proportion of population ≥ 65; and 2) strokes in CMS beneficiaries, using CDC/CMS county-level values for annual stroke hospitalizations.
Results: During the 4 year study period, the number of active MSUs grew from 1 in 2014, 2 in 2015, 6 in 2016, to 13 in 2017, all operating in distinct counties, including 7 (54%) in Census-defined large central metros with high population density, 3 (23%) in large fringe metros with moderately high population density, 3 (23%) in medium/small metros with moderate population density, and 0 (0%) in rural areas. The population over age 65 with MSU access increased from 153,860 in 2014, 315,884 in 2015, 671,960 in 2016, to 1,495,896 in 2017. The number of annual CMS stroke hospitalizations in MSU-covered regions increased from 1,831 in 2014, 3,775 in 2015, 7,031 in 2016, to 15,566 in 2017. By the end of 2017, MSUs were positioned to provide service to 2.9% of all Medicare beneficiaries experiencing stroke hospitalization in the US.
Conclusions: In the short span of the first 4 years of MSU pilot programs in the United States, with only 13 vehicles in service, expanding MSU programs provide access to accelerated treatment for 3 of every 100 US Medicare beneficiaries. This early geomapping analysis indicates that, if demonstration projects confirm cost-effectiveness, supporting wider dissemination, MSU care could provide rapid therapy to a substantial proportion of older Americans with acute ischemic and hemorrhagic stroke.