Clinical Characteristics and In-Hospital Outcomes of Varying Definitions of Minor Stroke

Background and Purpose: A variety of definitions for minor stroke have been proposed. We aimed to compare the clinical characteristics and outcomes of minor stroke defined as the National Institutes of Health Stroke Scale (NIHSS) score ≤5 versus ≤3. Methods: We retrieved acute ischemic stroke patients with NIHSS score ≤5 in the CSCA study (China Stroke Center Alliance) between August 2015 and 2019. In-hospital clinical outcomes including all-cause mortality, stroke, and myocardial infarction were compared between the NIHSS score ≤5 and NIHSS score ≤3 groups using absolute standardized differences (ASD). Results: A total of 1 006 798 patients were registered in the CSCA program from 1476 hospitals, 472 352 patients had NIHSS score ≤5, of whom 356 314 patients had NIHSS score ≤3. The in-hospital composite events of death, myocardial infarction, or recurrent stroke were not significantly different between the NIHSS score ≤5 and NIHSS score ≤3 groups (5.6% [26 346/472 352] versus 5.2% [18 682/356 314]; ASD, 1.8). The in-hospital all-cause mortality (0.1% [443/472 352] versus 0.1% [255/356 314]; ASD, <0.01), recurrent ischemic stroke (5.3% [25 026/472 352] versus 5.0% [17 777/356 314]; ASD, 1.4), and hemorrhagic stroke (0.5% [2151/472 352] versus 0.4% [1475/356 314]; ASD, 1.5) were not significantly different between both the NIHSS score ≤5 and NIHSS score ≤3 groups. Conclusions: Our large-scale study identified that minor stroke using NIHSS scores ≤5 and ≤3 as the definition was comparable with each other regarding in-hospital all-cause mortality, recurrent stroke, and hemorrhagic stroke. This observation may be useful for future comparison studies and clinical trial design.