inter-rater reliability of modified alberta stroke program early computerized tomography score in patients with brain infarction

Background: The Alberta Stroke Program Early Computerized Tomography Score (ASPECTS) was used to detect significant early ischemic changes on brain CT of acute stroke patients. We designed the modified ASPECTS and compared it to the above system based on the inter-rater reliability. Methods: A cross-sectional validation study was conducted based on the inter-rater reliability. The CT images were chosen from the stroke data bank of Ghaem hospital, Mashhad in 2010. The inclusion criteria were the presence of middle cerebral artery territory infarction and performance of CT within 6 hours after stroke onset. Axial CT scans were performed on a third-generation CT scanner (Siemens, ARTX, Germany). Section thickness above posterior fossa was 10 mm (130 kV, 150 mAs). Films were made at window level of 35 HU. The brain CTs were scored by four independent radiologists based on the ASPECTS and modified ASPECTS. The readers were blind to clinical information except symptom side. Cochrane Q and Kappa tests served for statistical analysis. Results: 24 CT scans were available and of sufficient quality. Difference in distribution of dichotomized ≤7 and >7 ASPECT scores between four raters was significant (Q=13.071, df=3, p=0.04). Distribution of dichotomized <6 and ≥6 scores based on modified ASPECT system between 4 raters was not significantly different (Q=6.349, df=3, p=0.096). Conclusions: Modified ASPECT method is more reliable than ASPECTS in detecting major early ischemic changes in stroke patients candidated to tPA thrombolysis.