Hypodensity of >⅓ Middle Cerebral Artery Territory Versus Alberta Stroke Programme Early CT Score (ASPECTS): Comparison of Two Methods of Quantitative Evaluation of Early CT Changes in Hyperacute Ischemic Stroke in the Community Setting

Background— The one third middle cerebral artery territory (⅓ MCA) method and the Alberta Stroke Program Early CT Score (ASPECTS) were used to detect significant early ischemic changes (EIC) on CT brain of acute stroke patients. We sought to compare the reliability of the 2 methods in routine clinical practice. Methods— Eighty consecutive patients admitted to a community hospital in Hong Kong with suspected acute ischemic stroke and a CT brain scan performed within 6 hours of symptom onset were included. Five blinded observers (1 neurologist, 2 general radiologists, and 2 neuroradiologists) independently evaluated the scans, using the ATLANTIS/CT Summit criteria for >⅓ MCA involvement, and ASPECTS ≤7. Kappa statistics were used to determine interobserver agreement. Results— Significant EIC were present in 11.4% of the scans with the ⅓ MCA method, and 19.4% with ASPECTS. For >⅓ MCA involvement, all observers agreed in 57 cases (71%), with moderate interobserver agreement (&kgr;=0.49). For ASPECTS ≤7, all observers agreed in 34 cases (42%), with fair interobserver agreement (&kgr;=0.34). After prevalence and bias adjustments, substantial (prevalence-adjusted bias-adjusted &kgr; [PABAK]=0.74) and moderate (PABAK=0.44) agreements were found for the ⅓ MCA method and ASPECTS respectively. Conclusions— The ⅓ MCA method was more reliable in detecting significant EIC on CT brain within 6 hours of stroke onset in routine clinical practice, whereas ASPECTS was able to detect significant EIC in a higher proportion of these early scans.