Treatment strategy, stroke severity, and functional outcomes in acute ischemic stroke: evidence of effect modification in a real-world cohort.

OBJECTIVES: To explore the association between treatment strategy and functional outcomes in acute ischemic stroke (AIS) and assess whether this association is modified by stroke severity and imaging findings. METHODS: We conducted a retrospective single-center cohort study of adults with AIS treated between March 2023 and September 2025 at a tertiary stroke center in Central Asia. Patients were categorized into intravenous thrombolysis, selective intra-arterial thrombolysis, or angiography without thrombolysis. The primary outcome was poor functional outcome, defined as modified Rankin Scale (mRS) score ≥ 3 at discharge. Multivariable logistic regression and interaction analyses were performed. RESULTS: A total of 247 patients were included, of whom 60.3% had poor functional outcomes. Outcomes differed significantly between treatment groups (p = 0.024), with favorable outcomes more common after intravenous thrombolysis than after selective intra-arterial thrombolysis or angiography without thrombolysis. In multivariable analysis, both selective intra-arterial thrombolysis (OR 2.23, 95% CI 1.04-4.78) and angiography without thrombolysis (OR 2.70, 95% CI 1.23-5.92) were associated with higher odds of poor outcome than intravenous thrombolysis. A significant interaction was observed between treatment strategy and admission NIHSS (Pinteraction < 0.001), whereas the interaction with MRI-confirmed ischemia was not significant (Pinteraction = 0.066). Admission NIHSS demonstrated modest predictive performance (AUC 0.65, 95% CI 0.56-0.74). DISCUSSION: In this exploratory observational cohort, treatment strategy was associated with functional outcome at discharge, and this association varied according to baseline stroke severity. Because treatment allocation was non-random and residual confounding cannot be excluded, these findings should be considered hypothesis-generating rather than causal evidence of treatment effectiveness.