The validity and reliability of signs of early infarction on CT in acute ischaemic stroke

It has been suggested that subtle signs of early cerebral infarction on CT are important indicators of outcome and of the effect of thrombolytic treat ment in acute ischaemic stroke. We studied these signs prospectively, in 26 0 patients with an anterior circulation stroke from a European-Australian r andomised trial of lubeluzole in acute ischaemic stroke. Interobserver reli ability was assessed by means of the x, statistic. The validity of the earl y signs was assessed by comparing the assessments of the first CT with anot her CT at 1 week after the onset of stroke, and with stroke outcome at 12 w eeks. Each initial CT study was assessed by two of a group of five reviewer s, who were blinded to each other's assessments and to the findings on the follow-up CT. The images were assessed twice, once without clinical informa tion and again after disclosure of the side (left or right hemisphere) of t he lesion. All reviewers were experienced clinicians with a special interes t and training in vascular neurology and CT. The median time between stroke onset and the first CT was 3.2 h; 59 % of the patients were imaged within 3 h and 77 % within 6 h. More than half of the patients (52 %) had a large middle cerebral artery territory (MCA) infarct on follow-up CT. Chance-adju sted interobserver agreement (x) for any early infarct was 0.27 (95 % confi dence interval (CI): 0.15 to 0.39), Agreement ( x) on the extent of a middl e cerebral artery (MCA) infarct and on the indication for treatment with re combinant tissue plasminogen activator (rt-PA) was fair: 0.37 and 0.35, res pectively. Patients with early signs of an infarct of more than 1/3 of the MCA territory were more likely to have a large MCA infarct on follow-up CT (odds ratio 5.7, 95 % confidence interval 2.8-11.5); the positive and negat ive predictive value of these signs was 81 % and 57 %, respectively. Chance -adjusted interobserver agreement on early, subtle signs of a large MCA ter ritory infarct on CT by neurologists was thus no more than fair, and the ac curacy of prediction of actual infarct size on the basis of these signs onl y moderate, under circumstances which resemble everyday clinical practice.