Mild traumatic brain injury (mTBI) accounts for most head injury emergency department (ED) presentations, yet only a minority of patients have acute intracranial lesions on CT, leading to unnecessary scans. Point‑of‑care (POC) biosensing offers a solution by rapidly quantifying biomarkers to inform CT decisions. This review evaluates POC‑compatible strategies for ultra‑early mTBI triage, focusing on platforms, matrix effects, and benchmarking aligned with CT‑based decision‑making. Key precedents include S100B integration into Scandinavian guidelines (safe CT reduction) and FDA‑cleared GFAP/UCH‑L1 testing to rule out head CT in adults with suspected mTBI (GCS 13‑15) within 12 hours. The review synthesizes the biomarker landscape, analyzes POC sensing modalities, and proposes a practical validation framework. A critical finding is that hemolysis significantly elevates UCH‑L1, a vulnerability that must be addressed. The most reliable path for biosensor translation is to anchor development to the ED CT‑triage use case, emphasizing decision‑point robustness and resilience to real‑world sample variability over pure analytical sensitivity.
Introduction
mTBI represents the majority of head injuries in EDs, but only a small fraction have acute intracranial lesions on CT. This creates a clinical dilemma: high sensitivity for significant injuries must be balanced against avoiding unnecessary CT (cost, radiation, workflow burden). The most implementable biomarker use case is early triage/rule‑out of acute intracranial lesions within a defined time window. Two precedents support this: (1) Scandinavian Neurotrauma Committee (SNC) guidelines incorporating S100B, which in validation studies reduced CT by ~32% with high safety; (2) FDA‑cleared GFAP/UCH‑L1 testing (Banyan Brain Trauma Indicator, i‑STAT TBI Plasma) for adults with suspected mTBI (GCS 13‑15) within 12 hours, where a negative result is associated with absence of CT lesions. This review focuses on POC biosensing for CT triage, covering biomarkers, sensing platforms, analytical validation, and ED deployment.
Biomarkers for ED Triage: S100B, GFAP, and UCH‑L1
S100B: Astrocyte‑enriched protein. Its strongest value is within strict algorithms (SNC guidelines), showing CT reduction potential. However, specificity is reduced by extracranial sources. For POCT, classification stability near the decision threshold is more important than ultra‑low LOD.
GFAP: Astroglial intermediate filament protein, strongly associated with intracranial lesions. It is the dominant marker for lesion detection and is part of the FDA‑cleared pair.
UCH‑L1: Neuron‑enriched protein reflecting neuronal injury. Critical vulnerability: hemolysis significantly elevates UCH‑L1 from 400 mg/L hemoglobin, a common issue in trauma samples. POCT designs must include hemolysis detection or resilient calibration.
Point‑of‑Care Biosensing Modalities
Cleared POCT systems (i‑STAT TBI Plasma, VIDAS TBI): Cartridge‑based, ~15 min turnaround, semi‑quantitative interpretation ("Elevated"/"Not Elevated"). They anchor biosensor development to a validated intended use and operational constraints.
Electrochemical immunosensors: Compact, low‑power, but face matrix‑driven variability (fouling, drift). Success depends on anti‑fouling strategies and rigorous interference testing, not just low LOD in buffer.
Optical/imaging readouts: Multiplexing potential, smartphone‑enabled, but vulnerable to illumination, turbidity, and background chromophores. Require controlled acquisition and internal references.
Electrochemiluminescence (ECL)/chemiluminescence: High sensitivity, low background, multiplex‑friendly. Translational barriers include manufacturability and cross‑talk in multiplex workflows.
Analytical Validation and Clinical Benchmarking
Validation must be backward‑designed from the decision endpoint (CT rule‑out). Key domains:
Precision near cutoffs: small bias or drift can flip a decision.
Interference testing: hemolysis is decisive for UCH‑L1. Graded hemolysis panels and invalid/repeat rules are essential.
Matrix effects: serum vs. plasma differences matter; validation must use matrix‑matched materials.
Method comparison: against reference assays (e.g., ELISA) in matched clinical samples.
Endpoint‑aligned clinical performance: sensitivity and NPV at prespecified cutoffs. The ALERT‑TBI study reported 97.6% sensitivity and 99.6% NPV for GFAP/UCH‑L1 in ruling out CT lesions.
Benchmarking against SNC guideline pathways: provides real‑world CT reduction estimates (~32%) and safety outcomes.
ED Deployment Considerations
Pathway adherence: Even sensitive biomarkers fail to reduce CT if clinicians ignore results. In real‑world S100B implementation, nearly 40% of negative results were ignored. Training and workflow integration are essential.
Interpretation rules: Decision‑ready outputs ("Elevated"/"Not Elevated") and clear repeat/invalid logic are needed.
Operational robustness: Devices must tolerate temperature, altitude, vibration, and sample quality issues (hemolysis, lipemia).
Failure modes: Hemolysis is a known vulnerability for UCH‑L1. POCT systems must detect or mitigate it.
How to Design Biosensors for CT Triage
Define success by decision‑region robustness, not analytical LOD. Focus validation on concentration ranges around cutoffs.
Report key metrics: repeatability, lot‑to‑lot variability, interference (graded hemolysis), method comparison, and decision‑level performance (sensitivity, NPV, invalid rate).
Include human factors: minimal sample prep, clear outputs, and pathway integration.
Comparative Synthesis and Checklist
The review provides a platform‑by‑platform comparison table (cleared POCT, electrochemical, optical, ECL) and a validation checklist aligned with CT‑triage requirements. Essential elements: prespecified cutoffs, interference panels (hemolysis/lipemia/icterus), matrix‑matched calibration, and at least one comparator method.
Future Directions
Highest‑yield research is not adding more biomarkers but building systems that sustain decision performance across diverse ED environments. Priorities: decision‑region robustness, matrix‑resilient designs, and standardized "camera‑to‑answer" or cartridge‑to‑answer pipelines with traceable calibration and failure handling.
Limitations
This is a practical roadmap, not a systematic review. Focused on adult ED mTBI (GCS 13‑15) within early sampling window; pediatric and prognostic applications not covered. Heterogeneity in specimen matrix, sampling windows, and cutoffs across studies affects apparent performance. Many prototypes remain under‑validated at the decision region.
Conclusions
The most reliable path for clinically credible biosensor translation is to frame development around the ED CT‑triage intended use, with a clearly defined endpoint and prespecified decision thresholds. The decisive barrier is not analytical sensitivity but performance stability under real‑world sample and workflow variability. Clinically persuasive work must emphasize precision and bias near cutoffs, explicit interference/matrix testing (especially hemolysis for UCH‑L1), and traceable calibration. When these decision‑level requirements are treated as core scientific deliverables, next‑generation POCT platforms can credibly reduce unnecessary CT and improve mTBI triage.
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The study was recently published in the Neurosurgical Subspecialties .
Neurosurgical Subspecialties (NSSS) is the official scientific journal of the Department of Neurosurgery at Union Hospital of Tongji Medical College, Huazhong University of Science and Technology. NSSS aims to provide a forum for clinicians and scientists in the field, dedicated to publishing high-quality and peer-reviewed original research, reviews, opinions, commentaries, case reports, and letters across all neurosurgical subspecialties. These include but are not limited to traumatic brain injury, spinal and spinal cord neurosurgery, cerebrovascular disease, stereotactic radiosurgery, neuro-oncology, neurocritical care, neurosurgical nursing, neuroendoscopy, pediatric neurosurgery, peripheral neuropathy, and functional neurosurgery.
