Agreement and variability in the interpretation of early CT changes in stroke patients qualifying for intravenous rtPA therapy

Background and Purpose-Ischemic changes identified on CT scans performed in the first few hours after stroke onset, which are thought to possibly repr esent early cytotoxic edema and development of irreversible injury, may hav e important implications for subsequent treatment However, insecurity and c onflicting data exist over the ability of clinicians to correctly recognize and interpret these changes. We performed a detailed review of selected ba seline CT scans from the NINDS rt-PA Stroke Trial to test agreement among e xperienced stroke specialists and other physicians on the presence of early CT ischemic changes. Methods-Seventy baseline CT scans from the NINDS Stroke Trial were read and classified for the presence or absence of various early findings of ischem ia by 16 individuals, including NINDS trial investigators, other neurologis ts, other emergency medicine physicians, and radiology or stroke fellows. C T scans included normal scans and scans from patients who later developed s ymptomatic intracranial hemorrhage, as well, as scans on which the NINDS rt -PA Stroke Trial neuroradiologist identified clear-cut early CT changes. Fo r each CT finding, kappa-statistics were used to assess the proportion of a greement beyond chance. Results-kappa-Values (95% confidence interval [CI]) ranged from 0.20 (-0.20 , 0.61) (fair agreement) to 0.42 (0.37, GAS) (moderate agreement) among the 16 viewers, and the kappa-value was only 0.39 (0.29, 0.49) (fair) in answe r to the question "do early CT changes involve more than one third of the M CA [middle cerebral artery] territory?" There was substantial variability w ithin each specialty group and between groups. kappa-Values were only fair to moderate even among physicians experienced in selecting and treating acu te stroke patients with rtPA, Observed agreement ranged from 68% to 85%. Ph ysicians agreed on the finding of early CT changes involving >33% of the MC A territory 77% of the time, although the kappa-value of 0.39 suggested onl y moderate: agreement beyond chance. Conclusions-There is considerable lack of agreement, even among experienced clinicians, in recognizing and quantifying early CT changes. Improved meth ods of recognizing and quantifying early ischemic brain damage are needed.