Biomarkers of brain injury after cardiac arrest; a statistical analysis plan from the TTM2 trial biobank investigators

Background: Several biochemical markers in blood correlate with the magnitude of brain injury and may be used to predict neurological outcome after cardiac arrest. We present a protocol for the evaluation of prognostic accuracy of brain injury markers after cardiac arrest. The aim is to define the best predictive marker and to establish clinically useful cut-off levels for routine implementation. Methods: Prospective international multicenter trial within the Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest (TTM2) trial in collaboration with Roche Diagnostics International AG. Samples were collected 0, 24, 48, and 72 hours after randomisation (serum) and 0 and 48 hours after randomisation (plasma), and pre-analytically processed at each site before storage in a central biobank. Routine markers neuron-specific enolase (NSE) and S100B, and neurofilament light, total-tau and glial fibrillary acidic protein will be batch analysed using novel Elecsys® electrochemiluminescence immunoassays on a Cobas e601 instrument. Results: Statistical analysis will be reported according to the Standards for Reporting Diagnostic accuracy studies (STARD) and will include comparisons for prediction of good versus poor functional outcome at six months post-arrest, by modified Rankin Scale (0–3 vs. 4–6), using logistic regression models and receiver operating characteristics curves, evaluation of mortality at six months according to biomarker levels and establishment of cut-off values for prediction of poor neurological outcome at 95–100% specificities. Conclusions: This prospective trial may establish a standard methodology and clinically appropriate cut-off levels for the optimal biomarker of brain injury which predicts poor neurological outcome after cardiac arrest

Brain injury markers in blood associate with generalised oedema on computed tomography after cardiac arrest

Introduction. According to the 2021 ERC/ESICM guideline recommen-dations, elevated neuron-specific enolase [NSE] levels as well as diffuseand extensive anoxic damage on neuroimaging are predictors of poorneurological outcome after cardiac arrest.(1) We previously describedthat NSE is elevated in patients with generalised oedema on com-puted tomography [CT]. (2).Objectives. In this study, we aim to examine the novel brain injurymarkers serum neurofilament light [NFL], glial fibrillary acidic protein[GFAP] and total-tau [tau] to predict the presence of generalised brainoedema.Methods. Retrospective analysis of patients examined with CT onclinical indication within the Target Temperature Management afterout-of-hospital cardiac arrest [TTM] trial. (2,3) Serum samples fromthe biobank sub study were prospectively collected at 48 h post arrestand analysed after trial completion as published. (4–7) The neuronalmarker NSE, the neuroaxonal injury markers NFL and tau and theastrocytic injury marker GFAP were correlated with the presence ofgeneralised oedema on CT, assessed by local radiologists through vis-ual evaluation. The prognostic accuracy of NSE ≥ 60 ug/l for predictinggeneralised oedema was also analysed.Results. 192 patients had data available on all four biomarkers at 48 hand were examined with CT < 168 h post arrest. Brain injury markerswere significantly higher in patients with generalised oedema as com-pared to patients without oedema on CT scans performed 24–168 hafter ROSC (p < 0.001) (Fig. 1A–D). For CT scans performed < 24 h, onlyNSE levels showed a significant correlation (p < 0.05). Biomarkers pre -dicted generalised oedema with area under the receiver operatingcharacteristics curve [AUC] 67.5–73.2% for CT scans performed < 24 h(n = 111), with no statistically significant difference between themarkers ( Fig. 2A). For scans performed 24–168 h (n = 81) AUC for pre -dicting generalised oedema was 78.1%-82.9%, with no statisticallysignificant difference between the markers. NSE ≥ 60 ug/l at 48 h, asrecommended by guidelines, predicted generalised oedema with 81%(95%CI 67–90%) sensitivity and 77% (95%CI 62–87%) specificity.Conclusion. Concentrations of all evaluated brain injury markerswere significantly higher in patients with generalised oedema on CTperformed after the first 24 h post arrest. Biomarker concentrationsindicate whether generalised oedema on CT is likely and may thus beclinically useful for deciding if a CT scan is sufficient for prognostica-tion or if a MRI is more appropriate

Brain injury markers in blood predict signs of hypoxic ischaemic encephalopathy on head computed tomography after cardiac arrest

Background/Aim: Signs of hypoxic ischaemic encephalopathy (HIE) on head computed tomography (CT) predicts poor neurological outcome after cardiac arrest. We explore whether levels of brain injury markers in blood could predict the likelihood of HIE on CT. Methods: Retrospective analysis of CT performed at 24–168 h post cardiac arrest on clinical indication within the Target Temperature Management after out-of-hospital cardiac arrest-trial. Biomarkers prospectively collected at 24- and 48 h post-arrest were analysed for neuron specific enolase (NSE), neurofilament light (NFL), total-tau and glial fibrillary acidic protein (GFAP). HIE was assessed through visual evaluation and quantitative grey-white-matter ratio (GWR) was retrospectively calculated on Swedish subjects with original images available. Results: In total, 95 patients were included. The performance to predict HIE on CT (performed at IQR 73–116 h) at 48 h was similar for all biomarkers, assessed as area under the receiving operating characteristic curve (AUC) NSE 0.82 (0.71–0.94), NFL 0.79 (0.67–0.91), total-tau 0.84 (0.74–0.95), GFAP 0.79 (0.67–0.90). The predictive performance of biomarker levels at 24 h was AUC 0.72–0.81. At 48 h biomarker levels below Youden Index accurately excluded HIE in 77.3–91.7% (negative predictive value) and levels above Youden Index correctly predicted HIE in 73.3–83.7% (positive predictive value). NSE cut-off at 48 h was 48 ng/ml. Elevated biomarker levels irrespective of timepoint significantly correlated with lower GWR. Conclusion: Biomarker levels can assess the likelihood of a patient presenting with HIE on CT and could be used to select suitable patients for CT-examination during neurological prognostication in unconscious cardiac arrest patients