The aim of this study was to determine the prognostic value and optimal sampling time of serum S-100B protein for the prediction of poor neurological outcomes in post-cardiac arrest (CA) patients treated with therapeutic hypothermia (TH). Methods: We prospectively measured serum S100 calcium binding protein beta subunit (S-100B protein) levels 12 times (0-96 hours) after the return of spontaneous circulation (ROSC). The patients were classified into two groups based on cerebral performance

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... ory (CPC): the good neurological outcome group (CPC 1-2 at 6 months) and the poor neurological outcome group (CPC 3-5). We compared serial changes and serum S-100B protein levels at each time point between the two groups and performed receiver operating characteristic curve analysis for the prediction of poor neurological outcomes. Results: A total of 40 patients were enrolled in the study. S-100B protein levels peaked at ROSC (0 hour), decreased rapidly to 6 hours and maintained a similar level thereafter. Serum S-100B protein levels in the poor CPC group (n = 22) were significantly higher than in the good CPC group (n = 18) at all time points after ROSC except at 4 hours. The time points with highest area under curve were 24 (0.829) and 36 (0.837) hours. The cut-off value, the sensitivity (24/36 hours) and specificity (24/36 hours) for the prediction of poor CPC at 24 and 48 hours were 0.221/0.249 ug/L, 75/65% and 82.4/94.1%, respectively. Conclusions: Serum S-100B protein was an early and useful marker for the prediction of poor neurological outcomes in post-CA patients treated with TH and the optimal sampling times were 24 and 36 hours after ROSC.