Supplementary Material for: CT-based and CTA-based posterior circulation ASPECTS in acute basilar artery occlusion: An Agreement Study

Background and purpose: The purpose of the present study was to evaluate the agreement on pc-ASPECTS (posterior circulation Acute Stroke Prognosis Early Computed Tomography Scores) based on non-contrast CT (NCCT) and CT angiography (CTA) source images in patients with acute basilar artery occlusion (BAO).
Methods: We prospectively enrolled consecutive patients with acute BAO from January 2022 to August 2022 at The First Affiliated Hospital of University of Science and Technology of China. The NCCT and CTA were scored independently by 15 raters during 2 different reading sessions at least 3 weeks apart. The pc-ASPECTS based on NCCT and CTA were analyzed on the full scale or were dichotomized (0-6 versus 7-10, 0-7 versus 8-10 and 0-8 versus 9-10). The level of agreement was measured using Fleiss κ Statistics.
Results: The median (IQR) CT-based pc-ASPECTS was 8 (6.75-9). The interrater agreement for CT-based pc-ASPECTS (κ=0.133 [0.132-0.133]) and CTA-based pc-ASPECTS (κ=0.204 [0.203-0.204]) was slight for all raters. Dichotomizations obtaining the highest concordance for the CT-based pc-ASPECTS (0-6 versus 7-10) and the CTA-based pc-ASPECTS (0-8 versus 9-10) failed to increase the interrater agreement to a substantial level (κ=0.350 [0.348-0.351] and 0.396 [0.395-0.398], respectively). Intrarater agreement for global CT-based pc-ASPECTS was less than substantial for the 14/15 raters and reached the level of substantial for the 3/15 raters with dichotomization.
Conclusions: Agreement between clinicians assessing CT-based and CTA-based pc-ASPECTS cannot be sufficient to make reproducible clinical decisions and assessments. The dichotomization failed to improve interrater and intrarater agreement to the level of substantial.