Abstract 26: Agreement Between TOAST and CCS Classification in SiGN

Abstract

Background: The heterogeneity of ischemic stroke has relevance for determination of risk for recurrence, prediction of outcomes, and identification of genetic risk factors. Among the many systems created for classifying patients into subtypes of stroke, the Trial of Org10172 Acute Stroke Trial (TOAST) and Causative Classification of Stroke (CCS) systems are among the most commonly used. Both systems generate similar subtype diagnoses although the two systems use different criteria for subtype assignment. The purpose of this study was to assess the level of agreement between subtype classification made using these two systems. Methods: Study subjects included 14,106 adult men and women accrued in the NINDS Stroke Genetics Network (SiGN) across 21 centers in the US and Europe classified independently using both with TOAST and CCS. Kappa statistics were calculated for the five major ischemic stroke subtypes common to both systems. Results: The overall agreement between TOAST and CCS was moderate (agreement rate, 70%; kappa = 0.60, 95% confidence interval [CI], 0.59 to 0.61). Agreement varied widely across study sites, ranging from 28% to 90%. Agreement on specific subtypes was highest for large artery atherosclerosis (kappa, 0.71; 95% CI, 0.70 to 0.73) and lowest for small artery occlusion (kappa = 0.56, 95%CI, 0.54 to 0.58). Conclusion: Agreement between TOAST and CCS diagnoses was only moderate. Caution is warranted when comparing or combining results based upon the two systems. Re-phenotyping using one system should be encouraged when possible to ensure valid results. Table: Cross-classification of stroke subtypes by TOAST and CCS