Interobserver Agreement of ASPECT Score Distribution for Noncontrast CT, CT Angiography, and CT Perfusion in Acute Stroke

Abstract

Background and Purpose— The Alberta Stroke program early CT score (ASPECTS) is a semiquantative scale for estimating extent and distribution of early ischemic changes within the MCA territory in the acute stroke setting. Good interobserver agreement of total ASPECTS is demonstrated for noncontrast CT (NCCT) and other imaging modalities. Our purpose is to assess interobserver agreement for individual ASPECTS regions for different imaging modalities. Methods— One hundred and eighty-one consecutive patients presenting with acute stroke symptoms within 4.5 hours of onset were included. Four readers assigned total and individual ASPECTS for NCCT, CT angiography source images (CTA-SI), and CTP maps of cerebral blood volume (CTP-CBV). Interobserver agreement was assessed by measuring internal consistency and concordance of total and individual ASPECTS using Cronbach’s α and intraclass correlation coefficient, respectively. Results— Total ASPECTS demonstrated very good concordance and internal consistency for all 3 modalities. Intraclass correlation coefficient and Cronbach’s α were 0.834 and 0.859 for NCCT, 0.876 and 0.894 for CTA, and 0.903 and 0.911 for CTP-CBV, respectively. Performance for individual ASPECTS regions was inferior to total ASPECTS, but incremental improvement in interobserver reliability was demonstrated for NCCT, CTA-SI, and CTP-CBV, respectively. Highest concordance was shown for caudate, lentiform, and M1–M3, whereas performance for internal capsule and M4–M6 was poorer. Conclusions— CTP-CBV demonstrates the highest interobserver agreement for individual ASPECTS regions.