Differentiation Of Stroke Subtype Classification By ASCO And Modified TOAST

Background and purpose: A reliable and precise etiologic classification of ischemic stroke is highly important in the treatment and prognostication.The ASCO classification of stroke, as a new approach for stroke subtyping, representing a new stroke phenotyping concept which described as 'complete stroke phenotyping classification', may improve the accuracy of classification and availability of clinical information by improve subtype assignment. In this classification system, every patients can be characterized by A-S-C-O: A for atherosclerosis; S for small vessel disease; C for cardiac source; O for other cause. Each of the 4 phenotypes is graded 1, 2, or 3 according to the levels of clinical and laboratory evidence. One for 'definitely a potential cause of the index stroke', 2 for'causality uncertain', 3 for 'unlikely a direct cause of the index stroke but disease is present'. When the disease is completely absent, the grade is 0; when grading is not possible due to insufficient work-up, the grade is 9. Based on ASCO subtype assignment, ASCO classification may also reduce the proportion of patients classified as cause undetermined.The modified TOAST classification system, which was the most commonly used in classifying cause of ischemic stroke, defined five causes of stroke after referring the clinical information and test, which include: Atherothrombosis, Small Artery Disease, Cardioembolism, Other Determined Etiology and Undetermined Etiology. This classification system had higher accuracy and reliability compared with classical TOAST diagnostic criteria (the Trial of ORG 10172 in the Acute Stroke Treatment). However, the modified TOAST never changed the 'scheme' of TOAST which paid so much attention to 'the only most likely cause(s) of stroke' that caused neglect to other complicated stroke etiology. Under this scheme especially, patients with more than two possibility causes were classified as Undetermined Etiology, thus losing more information and enlarged proportion of Undetermined Etiology subtype.Whether ASCO classification would reduce the proportion of patients classified as undetermined cause compared with the improved TOAST is worthy of further investigation. A previous study which compared the differentiation of stroke subtype classification to undetermined categories by TOAST, ASCO and Causative Classification System, indicated ASCO grade 1 did not reduce the proportion of cause undetermined cases compared with TOAST. It is still unknown that the differentiation between ASCO and modified TOAST to reduce the proportion of undetermined etiology, we aimed to address the hypothesis that ASCO would reduce the proportion of patients classified undetermined etiology compared with modified TOAST in a large first-ever acute ischemic stroke patients group. We also described the agreement between each subtypes which classified by ASCO and modified TOAST.Methods: Review data from 1375 consecutive admitted ischemic stroke cases in the Third Hospital of Hebei Medical University between 2007 and 2010. 425 first-ever acute ischemic stroke patients were selected, the cause of ischemic stroke was classified according to the ASCO criteria and modified TOAST criteria. The McNemar test and measurement ofκstatistic were used to compare the difference and agreetment between the two approaches.Results: When ASCO grade 1, more patients were classified as atherosclerosis(60.2% vs 57.9%; P=0.132) and fewer as small artery disease and cardiac disease subtype (13.4% vs 14.8% and 8.5% vs 8.7%; p: 0.238 and 1.000, respectively) compared with modified TOAST. ASCO grade 1 did not reduce the proportion of cause undetermined patients when compared with modified TOAST (15.5% vs 16.2%; p=0.795). The same ten patients were diagnosed as other cause subtype by ASCO grade 1 and modified TOAST. Agreement was showed in every subtype categories between the two kinds of classification system. Agreement for atherosclerotic cause and small artery disease was very good (allκover 0.81), and for the cardiac disease subtype was good (κ: 0.61 to 0.8). Among the 425 stroke patients, ASCO grades 1 to 3 identified patients with atherosclerotic cause (76.0%), small artery disease (46.4%) and cardiac disease(11.3%), no other cause patients were identified extra.Conclusion: There is a moderately high agreement between ASCO and modified TOAST classification in all subtypes except′undetermined′etiology. ASCO grade 1 did not reduce the proportion of cause undetermined patients when compared with modified TOAST.