Stroke subtype classification: A comparative study of ASCO and modified TOAST

Abstract

Background and purposeThe ASCO stroke classification may be an improvement over the modified TOAST for etiological diagnoses. We aimed to compare the differences in stroke subtype classification between these two classification system. MethodsSelected for this study were 425 first-time acute ischemic stroke patients. For each, the cause of ischemic stroke was classified according to both the ASCO and modified TOAST criteria. The κ statistic and McNemar test were used to compare the similarities and differences, respectively, between the two approaches. ResultsMore patients were classified as having an atherosclerotic etiology under the ASCO 1 category than the modified TOAST system (60.2% vs. 57.9%; P=0.132). There was no significant difference between the proportion of patients with undetermined etiology as defined by the ASCO 1 and the modified TOAST (15.5% vs. 16.2%; P=0.795). Both the modified TOAST and ASCO-1 correctly identified all patients with etiology “other cause”. Agreement between the two classification systems was high in every subtype category except ‛undetermined’ (κ>0.81 for atherosclerosis, κ=0.61 to κ=0.8 for cardiac disease, and κ=0.480 for undetermined). When ASCO-1 to ASCO 3 were applied, atherosclerosis was identified as the cause in 76.0% of patients, small artery disease in 46.4%, and cardiac disease in 11.3%. ConclusionThere is a moderately high agreement between the ASCO and modified TOAST classification schemes in all subtypes except that of “undetermined” etiology. Application of ASCO-1 did not reduce the proportion of patients ‘undetermined’ etiology compared to modified TOAST.