Evaluation of serum S100B as a surrogate marker for long-term outcome and infarct volume in acute middle cerebral artery infarction

BACKGROUND: An easily accessible and valid surrogate marker for interventional stroke trials is needed. OBJECTIVE: To investigate the usefulness of various S100B serum measures to predict long-term outcome and infarct volume in patients with acute stroke. DESIGN: Inception cohort study. SETTING: Tertiary care university hospital. PATIENTS: Thirty-nine patients (mean +/- SD age, 69.1 +/- 11.5 years) with acute nonlacunar middle cerebral artery infarction presenting less than 6 hours after symptom onset. MAIN OUTCOME MEASURES: Functional outcome 6 months after stroke (modified Rankin scale score) and final infarct volume on day 7 by means of standardized volumetry of brain images. Serum S100B level was determined at hospital admission and 24, 48, 72, 96, 120, and 144 hours after symptom onset. RESULTS: Single S100B measures obtained 48 and 72 hours after stroke onset demonstrated the highest Spearman rank correlations with modified Rankin scale scores (rho = 0.68 and rho = 0.67, respectively; P<.001) and infarct volume (rho = 0.95 and rho = 0.94, respectively; P<.001). A 48-hour S100B value of 0.37 microg/L or less revealed a sensitivity of 0.87 and a specificity of 0.78 in predicting an independent functional outcome. In a multivariate model, S100B emerged as an outcome predictor that was independent of age, sex, stroke severity, etiology, lesion side, and risk factors. CONCLUSIONS: Single S100B values obtained 48 and 72 hours after stroke onset provide the highest predictive values with respect to functional outcome and infarct volume in nonlacunar middle cerebral artery infarction. More complex measures of the S100B kinetic (ie, area under the curve or peak value) were not superior. Therefore, these single S100B measures appear to be useful surrogate end points in acute interventional stroke trials.