Statistical Analysis
REGRESSION
The primary outcome was analyzed using a mixed-effects linear regression model, which included a random effect for cluster (CSC) and a fixed effect for exposure status (pre-AI vs post-AI). The model was adjusted for age, sex, and NIHSS. Secondary outcomes including time from emergency department arrival to IV tPA treatment, hospital length of stay, and time from CT scan initiation to EVT start were analyzed using the same method, adjusted for age, sex, and NIHSS. In sensitivity analysis, we also adjusted the model for time from trial initiation (in months) to more explicitly account for secular trends, as has been recommended for the analysis of stepped-wedge study designs.