INTERRATER RELIABILITY OF AN ETIOLOGIC CLASSIFICATION OF ISCHEMIC STROKE

Background and Purpose Precise identification of the cause of stroke i s critical to research and clinical practice. Published series of isch emic stroke show considerable variation in the proportion of cases cla ssified as atherosclerotic large-vessel disease, lacunar infarct, card ioembolic stroke, stroke of other known cause, and stroke of undetermi ned etiology. We describe the development and use of an etiology-speci fic classification of ischemic stroke. The interrater reliability of t he classification is then evaluated. Methods A total of 160 cases of i schemic strokes in young adults were reviewed by paired neurologists w ho assigned cases to prioritized categories. The results of paired rat ings were evaluated for each of the potential causes. Interrater agree ment was assessed by means of kappa, which is the chance-adjusted perc ent agreement Results For standard pairs, kappa was fair to good for a ll causes except lacunar stroke (kappa=0.31); however, pair-to-pair va riation was greatst for lacunar strokes. Strokes of undetermined cause and hematologic/other cause were of borderline fair reliability. Conc lusions The utility of a stroke classification system is dependent on its intended use. An etiologic classification is useful in studies of the epidemiology and pathophysiological basis of stroke. Fair to good reliability for an etiologic classification of stroke can be obtained when criteria an explicit.