Abstract 31: Magnitude of Benefit of Prehospital Mobile Stroke Unit vs Conventional ED Thrombolysis: Final Estimate Based on PHANTOM-S Observational Registry Study

Abstract

Background: Mobile stroke units (MSUs) enable faster start of IV thrombolytic therapy for acute ischemic stroke. We sought to estimate the magnitude of benefit arising from speedier lytic start upon functional outcomes at 3 months in patients with acute ischaemic who had received emergency mobile care or conventional care. Methods: In a prospective observational registry study in Berlin, ischemic stroke patients were treated with IV thrombolysis in a stroke emergency mobile (STEMO) vehicle or conventionally (normal ambulances and ED lytic start). Disability outcomes (modified Rankin Scale) at 3m were analyzed, adjusted for age, sex, afib, NIHSS, and intra-arterial treatment. For dichotomized mRS outcomes, benefit per thousand (BPT) and number needed to treat (NNT) were derived directly from the absolute risk difference. For disability shift across all 6 mRS levels, BPT and NNT were derived by joint outcome table multiple resampling. Results: Among 658 IV tPA-treated patients, 305 were treated in the MSU and 353 conventionally in ED. Of the 6 cutpoints on the mRS, 5 showed more favorable outcomes with MSU care and 1 with conventional care. The Table shows resulting BPT and NNT values. The dichotomized endpoint with the greatest group difference was disability-free (mRS 0-1) outcome, 62.7% STEMO vs 54.8% conventional, BPT 79, NNT 12.7. For the 6 possible dichotomizations of the mRS, the benefit per thousand patients ranged from -9 to 79. For benefit of improving by 1 or more mRS levels across all 6 transitions of the mRS, the BPT was 176 and NNT 5.7. Conclusions: This observational study, with adjustment for key prognostic features, estimates that out of every 1000 patients treated with MSU rather than conventional ED thrombolysis, 176 will have a less disabled final outcome, including 79 more who would be disability-free. Larger, formally-controlled clinical trials are needed, and under way, to confirm whether MSUs do confer these substantial clinical benefits.