Inter-rater reliability of the A-S-C-O classification system for ischemic stroke

Atherosclerosis-small vessel disease-cardiac source-other (A-S-C-O) is a new phenotypic system that categorizes stroke according to a combination of etiologic characteristics. The purpose of this study was to establish the inter-rater reliability of ischemic stroke subtyping by applying A-S-C-O criteria to retrospectively reviewed medical records. A total of 419 patients with acute ischemic stroke were classified according to A-S-C-O criteria by two stroke neurologists independently. Inter-rater reliability was assessed by means of the κ statistic. The neurologists agreed on A-S-C-O subtype diagnosis for only 190 of the 419 patients (45.3%). The κ statistics for four stroke phenotypes were: (i) atherosclerosis, 0.786; (ii) small vessel disease, 0.798; (iii) cardiac source, 0.870; and (iv) other causes, 0.860. All p values were <0.001. Ischemic stroke can be reliably described with regard to four etiologic categories using the A-S-C-O system based on a review of medical records, whereas the overall agreement for stroke subtype diagnosis was only moderate.