ASPECT scoring to estimate >1/3 middle cerebral artery territory infarction.
OBJECTIVE
To compare the inter-observer reliability of Alberta Stroke Programme Early CT Scoring (ASPECTS) with the ICE (Idealize-Close-Estimate) method of estimating > 1/3 middle cerebral artery territory (MCAT) infarction amongst stroke neurologists and to determine how well ASPECT Scoring predicts > 1/3 MCAT infarctions in acute ischemic stroke (AIS).


BACKGROUND
The European Cooperative Acute Stroke Study suggested that > 1/3 involvement of the MCAT on early CT scan was a risk factor for symptomatic intracerebral hemorrhage (SICH) following treatment with tissue plasminogen activator (tPA) for AIS but, in the absence of a systematic method of estimation had poor interobserver reliability (Kappa 0.49). The ICE method was developed to standardize the approach to estimating early MCAT infarct size and has very good interobserver reliability (Kappa 0.72). ASPECTS has comparable interobserver reliability and is reported to predict both neurological outcome and SICH.


METHODS
Five stroke neurologists were tested with 40 AIS CT scans. Each performed blinded independent assessments of early ischemic changes with both ASPECTS and ICE. The reference standard was majority opinion of 1/3 MCAT determination of five neuroradiologists. A receiver operator curve (ROC) was constructed and likelihood ratios (LR) were calculated. Chance corrected agreement (kappa) and chance independent agreement (phi) were calculated for both methods, and analysis of variance was used to calculate reliability by intraclass correlation coefficient (ICC) for ASPECTS.


RESULTS
The LR for a positive test (> 1/3 MCAT) were extremely large and conclusive (approaching infinity) for ASPECTS of 0-3; were large and conclusive (30, 20, and 10) for ASPECTS of 4, 5, and 6 respectively; was an unhelpful 1 for ASPECTS of 7, and were again extremely large and conclusive (approaching zero) for ASPECTS of 8-10. A ROC plot supported an ASPECTS cutoff of < 7 as best for 1/3 MCAT estimation (94% sensitivity and 98% specificity). Kappa and Phi statistics were moderately good for both ASPECTS and ICE (0.7). ICC for ASPECTS was 0.8.


CONCLUSIONS
When experienced stroke neurologists utilize a formalized method of quantifying early ischemic changes on CT, either ASPECTS or ICE, the interobserver agreement and reliability are satisfactory. ASPECTS allows for a strong and conclusive estimation of the presence of 1/3 MCAT involvement and a cutoff point of < 7 results in best test performance.
Demaerschalk
Bart M
BM
Mayo Clinic College of Medicine, Department of Neurology, Mayo Clinic Arizona, 13400 East Shea Boulevard, Scottsdale, AZ 85259, USA.
Silver
Brian
B
Wong
Edward
E
Merino
Jose G
JG
Tamayo
Arturo
A
Hachinski
Vladimir
V
D000368:Aged; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000473:pathology*; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D020768:Middle Cerebral Artery / Q000473:pathology / Q000503:physiopathology; D009462:Neurology / Q000379:methods / Q000639:trends; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards