Goal: The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) on non-contrast computed tomography (NCCT) is dependent on the visibility of early ischemic change. The goal of our study was to evaluate whether time from ischemic stroke onset to initial NCCT influences the inter-rater variability and prognostic accuracy of ASPECTS for a 3-month functional outcome.
Materials and methods: Ischemic stroke patients treated with intravenous tissue plasminogen activator (IV-tPA) from 2007 to 2014 at the Royal Melbourne Hospital were included. ASPECTS were blindly assessed by 2 independent raters with inter-rater agreement determined by weighted kappa. Onset time to computed tomography time was dichotomized at the median (≤100 and >100 minutes). Outcome was assessed using the modified Rankin Scale. Logistic regression and receiver operating characteristic analysis were used to assess the prognostic utility of ASPECTS in the early and later time periods.
Results: There were 379 patients included. Inter-rater agreement was significantly lower in the early time period: kappa = .75 (95% confidence interval (CI), .59-.84) ≤ 100 minutes versus .92 (95% CI, .91-.93) > 100 minutes, P < .001. The distributions of absolute inter-rater differences in ASPECTS differed significantly between time epochs (P = .03). The prognostic accuracies of ASPECTS across time epochs were area under the receiver operating characteristic curve ≤ 100 minutes = .57 (95% CI, .50-.64) and >100 minutes = .66 (95% CI, .59-.73), P = .055.
Conclusions: This study demonstrated a significantly lower inter-rater agreement and a trend toward reduced prognostic accuracy of ASPECTS in earlier time periods. The use of ASPECTS to select patients for revascularization in early time windows may be unreliable.
Keywords: ASPECTS; CT; Ischemic; stroke; time.
Copyright © 2017 National Stroke Association. Published by Elsevier Inc. All rights reserved.