International Journal of Clinical Case Reports, 2025, Vol.15, No.6, 259-270 http://medscipublisher.com/index.php/ijccr 263 4 Monitoring Practice of Biomarkers in the Emergency Department 4.1 Specimen selection and monitoring time window In the emergency department (ED), for molecular monitoring of brain injury markers, it is necessary to first select appropriate biological specimens and determine the collection time. Blood, especially serum and plasma, is the most commonly used sample because it is easy to obtain and the processing and storage procedures are mature. Recent large-scale studies have standardized the collection of serum at multiple time points such as admission (0 h, 24 h, 48 h, and 72 h) after resuscitation to capture the dynamic changes in biomarker concentrations during the evolution of brain injury (Moseby-Knappe et al., 2021; Hoiland et al., 2022; Moseb-Knappe et al., 2022). Although cerebrospinal fluid (CSF) is more sensitive to some markers, its feasibility in the context of acute ED is limited and it is mostly used in research or specific clinical situations (Jeon et al., 2025; Guo, 2025). The timing of detection is particularly crucial for the interpretation and prediction of biomarker results. The variation patterns of different markers are not the same. S100B usually reaches its peak within the first few hours after cardiac arrest, while neuron-specific enolase (NSE) and neural filament light chain (NfL) increase gradually. Their predictive effects are best 48 to 72 hours after the recovery of heartbeat and respiration (Jeon et al., 2025; Kaminska et al., 2025). Blood collection within 6 to 24 hours after resuscitation can help quickly classify the patient's risk level. However, if continuous detection can be carried out in the first three days, the situation of brain injury can be grasped more comprehensively, making the prediction results more reliable (Moseby-Knappe et al., 2021; Hoiland et al., 2022; Moseb-Knappe et al., 2022). 4.2 Detection and interpretation of biomarkers in ED In ED, biomarkers are mostly detected by immunoassay methods, such as electrochemiluminescence or enzyme-linked immunosorbent assay (ELISA), which can conduct sensitive and specific quantitative analysis of brain injury proteins in blood samples (Humaloja et al., 2022). Result interpretation should simultaneously focus on the absolute levels and their temporal trends: for instance, persistently elevated NSE, NfL or S100B usually indicates a poor neurological prognosis, while normal or lower levels are often associated with better outcomes (Hoiland et al., 2022; Kaminska et al., 2025). At the same time, it should be recognized that the prediction thresholds of different institutions and detection platforms vary. Therefore, local reference ranges and critical values need to be established (Moseby-Knappe et al., 2022). In clinical interpretation, the effects of intervention methods such as hemolysis (which may increase NSE), extracranial injury (which may increase S100B), and target temperature management should be considered (Humaloja et al., 2022). Combining biomarkers with clinical physical examination, neuroimaging, and electrophysiological examination results for comprehensive judgment can help improve the accuracy of diagnosis and prognosis judgment, and reduce the risk of premature conclusion or improper conclusion (Sandroni et al., 2023). Under this premise, as long as a unified testing process is adopted and reporting standards such as STARD and TRIPOD are followed, the reliability and result consistency of biomarker monitoring in the emergency department can be further improved (Moseby-Knappe et al., 2022). 4.3 Biomarker monitoring and prognostic stratification Continuous monitoring of brain injury biomarkers in the emergency department can help doctors dynamically determine the risk level of patients and also provide support for important treatment decisions such as patient treatment and communication with family members. Research has found that key markers such as NfL, tau, and GFAP, if their values are low or normal, have a high value in excluding adverse prognosis and usually indicate that the patient's neurological recovery is good. However, if the value keeps rising, it is closely related to poor treatment outcomes (Fink et al., 2022; Kaminoska et al., 2025). Incorporating the changes of biomarkers over time into the prognosis assessment model can identify patients whose prognosis is difficult to determine solely based on clinical criteria. This can avoid premature discontinue of life support treatment and enable more rational allocation of intensive care resources (Moseby-Knappe et al., 2021; Sandroni et al., 2023).
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