© 2014 National Stroke Association. Background To assess the utility of previously developed scoring systems, we compared SEDAN, named after the components of the score (baseline blood Sugar, Early infarct signs and (hyper) Dense cerebral artery sign on admission computed tomography scan, Age, and National Institutes of Health Stroke Scale on admission), Totaled Health Risks in Vascular Events (THRIVE), Houston Intra-arterial Therapy (HIAT), and HIAT-2 scoring systems among patients receiving systemic (intravenous [IV] tissue plasminogen activator [tPA]) and endovascular (intra-arterial [IA]) treatments.Methods We retrospectively reviewed all IV tPA and IA patients presenting to our center from 2008-2011. The scores were assessed in patients who were treated with IV tPA only, IA only, and a combination of IV tPA and IA (IV-IA). We tested the ability of THRIVE to predict discharge modified Rankin scale (mRS) 3-6, HIAT and HIAT-2 discharge mRS 4-6, and SEDAN symptomatic intracerebral hemorrhage (sICH).Results Of the 366 patients who were included in this study, 243 had IV tPA only, 89 had IA only, and 34 had IV-IA. THRIVE was predictive of mRS 3-6 in the IV-IA (odds ratio [OR], 1.95; 95% confidence interval [CI], 1.30-2.91) and the IV group (OR, 1.71; 95% CI, 1.43-2.04), but not in the IA group. HIAT was predictive of mRS 4-6 in the IA (OR, 3.55; 95% CI, 1.65-7.25), IV (OR, 3.47; 95% CI, 2.26-5.33), and IV-IA group (OR, 6.48; 95% CI, 1.41-29.71). HIAT-2 was predictive of mRS 4-6 in the IA (OR, 1.39; 95% CI, 1.03-1.87) and IV group (OR, 1.36; 95% CI, 1.18-1.57), but not in the IV-IA group. SEDAN was not predictive of sICH in the IA or the IV-IA group, but was predictive in the IV group (OR, 1.54; 95% CI, 1.01-2.36).Conclusions Our study demonstrated that although highly predictive of outcome in the original study design treatment groups, prediction scores may not generalize to all patient samples, highlighting the importance of validating prediction scores in diverse samples.