Characterisation of serum total tau following paediatric traumatic brain injury: a case-control study

Predicting and improving outcome in severe pediatric traumatic brain injury

INTRODUCTION

Severe pediatric traumatic brain injury (spTBI), including abusive head trauma (AHT) in young children, is a major public health problem. Long-term consequences of spTBI include a large variety of physical, neurological, biological, cognitive, behavioral and social deficits and impairments.

AREAS COVERED

The present narrative review summarizes studies and reviews published from January 2019 to February 2024 on spTBI. Significant papers published before 2019 were also included. The article gives coverage to the causes of spTBI, its epidemiology and fatality rates; disparities, inequalities, and socioeconomic factors; critical care; outcomes; and interventions.

EXPERT OPINION

There are disparities between countries and according to socio-economic factors regarding causes, treatments and outcomes of spTBI. AHT has an overall poor outcome. Adherence to critical care guidelines is imperfect and the evidence-base of guidelines needs further investigations. Neuroimaging and biomarker predictors of outcomes is a rapidly evolving domain. Long-term cognitive, behavioral and psychosocial difficulties are the most prevalent and disabling. Their investigation should make a clear distinction between objective (clinical examination, cognitive tests, facts) and subjective measures (estimations using patient- and proxy-reported questionnaires), considering possible common source bias in reported difficulties. Family/caregiver-focused interventions, ecological approaches, and use of technology in delivery of interventions are recommended to improve long-term difficulties after spTBI.

Plasma Biomarkers of Traumatic Brain Injury in Adolescents With Sport-Related Concussion

Importance

Blood-based biomarkers may clarify underlying neuropathology and potentially assist in clinical management of adolescents with sport-related concussion (SRC).

Objective

To investigate the association between SRC and plasma biomarkers in adolescents.

Design, Setting, and Participants

Prospective cohort study in Canadian sport and clinic settings (Surveillance in High Schools and Community Sport to Reduce Concussions and Their Consequences study; September 2019 to November 2022). Participants were a convenience sample of 849 adolescent (ages 10-18 years) sport participants with blood samples. Data were analyzed from February to September 2023.

Exposures

Blood collection and clinical testing preseason (uninjured) and post-SRC follow-ups (ie, ≤72 hours, 1 week, and biweekly until medical clearance to return to play [RTP]).

Main Outcomes and Measures

Plasma glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase-L1 (UCH-L1), neurofilament light (NfL), and total tau (t-tau) were assayed. Group-level comparisons of biomarker levels were conducted between uninjured and post-SRC intervals (postinjury day [PID] 0-3, 4-10, 11-28, and >28) considering age and sex as modifiers. Secondary analyses explored associations between biomarker concentrations and clinical outcomes (Sport Concussion Assessment Tool, Fifth Edition [SCAT5] symptom scores and time to RTP).

Results

This study included 1023 plasma specimens from 695 uninjured participants (467 male participants [67.2%]; median [IQR] age, 15.90 [15.13-16.84] years) and 154 participants with concussion (78 male participants [51.0%]; median [IQR] age, 16.12 [15.31-17.11] years). Acute (PID 0-3) differences relative to uninjured levels were found for GFAP (female participants: 17.8% increase; β = 0.164; 95% CI, 0.064 to 0.263; P = .001; male participants: 17.1% increase; β = 0.157; 95% CI, 0.086 to 0.229; P < .001), UCH-L1 (female participants: 43.4% increase; β = 0.361; 95% CI, 0.125 to 0.596; P = .003), NfL (male participants: 19.0% increase; β = 0.174; 95% CI, 0.087 to 0.261; P < .001), and t-tau (female participants: -22.9%; β = -0.260; 95% CI, -0.391 to -0.130; P < .001; male participants: -18.4%; β = -0.203; 95% CI, -0.300 to -0.106; P < .001). Differences were observed for all biomarkers at PID 4 to 10, 11 to 28, and greater than 28 compared with uninjured groups. GFAP, NfL, and t-tau were associated with SCAT5 symptom scores across several PID intervals. Higher GFAP after 28 days post-SRC was associated with earlier clearance to RTP (hazard ratio, 4.78; 95% CI, 1.59 to 14.31; P = .01). Male participants exhibited lower GFAP (-9.7%), but higher UCH-L1 (21.3%) compared with female participants. Age was associated with lower GFAP (-5.4% per year) and t-tau (-5.3% per year).

Conclusions and Relevance

In this cohort study of 849 adolescents, plasma biomarkers differed between uninjured participants and those with concussions, supporting their continued use to understand concussion neuropathology. Age and sex are critical considerations as these biomarkers progress toward clinical validation.

Pediatric reference intervals for serum neurofilament light and glial fibrillary acidic protein using the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort

OBJECTIVES

Blood biomarkers have the potential to transform diagnosis and prognosis for multiple neurological indications. Establishing normative data is a critical benchmark in the analytical validation process. Normative data are important in children as little is known about how brain development may impact potential biomarkers. The objective of this study is to generate pediatric reference intervals (RIs) for serum neurofilament light (NfL), an axonal marker, and glial fibrillary acidic protein (GFAP), an astrocytic marker.

METHODS

Serum from healthy children and adolescents aged 1 to <19 years were obtained from the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort. Serum NfL (n=300) and GFAP (n=316) were quantified using Simoa technology, and discrete RI (2.5th and 97.5th percentiles) and continuous RI (5th and 95th percentiles) were generated.

RESULTS

While there was no association with sex, there was a statistically significant (p<0.0001) negative association between age and serum NfL (Rho -0.400) and GFAP (Rho -0.749). Two statistically significant age partitions were generated for NfL: age 1 to <10 years (lower, upper limit; 3.13, 20.6 pg/mL) and 10 to <19 years (1.82, 7.44 pg/mL). For GFAP, three statistically significant age partitions were generated: age 1 to <3.5 years (80.4, 601 pg/mL); 3.5 to <11 years (50.7, 224 pg/mL); and 11 to <19 years (26.2, 119 pg/mL).

CONCLUSIONS

Taken together with the literature on adults, NfL and GFAP display U-shaped curves with high levels in infants, decreasing levels during childhood, a plateau during adolescence and early adulthood and increasing levels in seniors. These normative data are expected to inform future pediatric studies on the importance of age on neurological blood biomarkers.

Acute Fluid Biomarkers for Diagnosis and Prognosis in Children with Mild Traumatic Brain Injury: A Systematic Review

BACKGROUND AND OBJECTIVE

Fluid biomarkers have the potential to improve the accuracy of diagnosis and prognosis in children with mild traumatic brain injury. Our primary objective was to assess the diagnostic and prognostic utility of acute blood and fluid biomarkers in children with mild traumatic brain injury.

METHODS

We performed a systematic review of the published literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. Fluid biomarker studies assessing pediatric mild traumatic brain injury diagnosis or prognosis were included if blood or fluids were sampled within 24 h of injury.

RESULTS

Thirty-two studies involving 4743 patients were included comprising 25 diagnostic studies and ten prognostic studies with three studies assessing both diagnosis and prognosis. Sixteen of the 25 diagnostic studies reported the area under the receiver operating characteristic curve (AUC) for predicting abnormal computed tomography scans of the head; S100 calcium binding protein B (S100B, N = 6 studies, AUC range 0.67-1.00), glial fibrillary acidic protein (N = 5, AUC range 0.41-0.85), ubiquitin C-terminal hydrolase (N = 3, AUC 0.59 and 0.83), neuron specific enolase (N = 1, AUC 0.99), total tau (N = 1, AUC 0.65), and interleukin-6 (N = 1, AUC 0.61). In four of the ten prognostic studies, increased acute serum S100B levels, tumor necrosis factor-α, or interleukin-8 were associated with post-concussive symptoms or fatigue from 3 to 12 months post-injury.

CONCLUSIONS

The largest amount of evidence supported the potential use of S100B, glial fibrillary acidic protein, and UCH-L1, but there was mixed accuracy for diagnosis and prognostication for all biomarkers in pediatric mTBI.

Associations of Plasma Tau with Amyloid and Tau PET: Results from the Community-Based Framingham Heart Study

Background

Associations of plasma total tau levels with future risk of AD have been described.

Objective

To examine the extent to which plasma tau reflects underlying AD brain pathology in cognitively healthy individuals.

Methods

We examined cross-sectional associations of plasma total tau with 11C-Pittsburgh Compound-B (PiB)-PET and 18F-Flortaucipir (FTP)-PET in middle-aged participants at the community-based Framingham Heart Study.

Results

Our final sample included 425 participants (mean age 57.6± 9.9, 50% F). Plasma total tau levels were positively associated with amyloid-β deposition in the precuneus region (β±SE, 0.11±0.05; p = 0.025). A positive association between plasma total tau and tau PET in the rhinal cortex was suggested in participants with higher amyloid-PET burden and in APOEɛ4 carriers.

Conclusions

Our study highlights that plasma total tau is a marker of amyloid deposition as early as in middle-age.

The Association Between Glasgow Coma Scale Scores and PTSD in Military Trauma Casualties: Does Mental Status Following Injury Play a Role in PTSD Development?

BACKGROUND

Posttraumatic stress disorder (PTSD) is prevalent among military personnel and may arise following a wide range of traumatic exposures. Consciousness level following traumatic injury may play a role in the development of PTSD, but its effects have been primarily investigated in the context of traumatic brain injury.

METHODS

Registry-based study surveying three databases documenting care from point of injury to long-term rehabilitation of traumatic injuries among military personnel. The study population was divided according to Glasgow Coma Scale (GCS) scores upon emergency department admission (GCS scores 15, 13 and 14, 9-12, and 3-8), with PTSD diagnoses being determined according to disability claim records. Multivariable logistic regression was utilized to determine the association between GCS score at admission and PTSD.

RESULTS

Overall, 3,376 military personnel hospitalized following traumatic injuries between 1997 and 2020 were included. The majority were male (92.3%), with a median age of 20 (interquartile range 19-22) at the injury time. Of these, 569 (16.9%) were diagnosed with PTSD according to disability claims, with a median follow-up time of 10.9 years. PTSD diagnosis was most prevalent (30.3% of patients), with a GCS score of 13 and 14. In the adjusted multivariable model, a GCS score of 13 and 14 was associated with significantly higher odds of PTSD diagnosis when compared to a GCS score of 15 (odds ratio 2.19, 95% CI, 1.21-3.88). The associations of other GCS groupings with PTSD diagnosis were nonsignificant.

CONCLUSIONS

Minimally impaired consciousness following traumatic injuries is associated with increased odds of PTSD. The role of patient awareness, analgesia, and sedation following an injury in developing PTSD warrants further investigation and could guide early diagnosis and preventive interventions.

Serum GFAP - pediatric reference interval in a cohort of Danish children

OBJECTIVES

Glial fibrillary acidic protein (GFAP) in blood is an emerging biomarker of brain injury and neurological disease. Its clinical use in children is limited by the lack of a reference interval (RI). Thus, the aim of the present study was to establish an age-dependent continuous RI for serum GFAP in children.

METHODS

Excess serum from routine allergy testing of 391 children, 0.4-17.9 years of age, was measured by a single-molecule array (Simoa) assay. A continuous RI was modelled using non-parametric quantile regression and presented both graphically and tabulated as discrete one-year RIs based on point estimates from the model.

RESULTS

Serum GFAP showed a strong age-dependency with declining levels and variability from infants to adolescents. The estimated median level decreased 66 % from four months to five years of age and another 65 % from five years to 17.9 years of age. No gender difference was observed.

CONCLUSIONS

The study establishes an age-dependent RI for serum GFAP in children showing high levels and variability in the first years of life.

Perioperative brain injury marker concentrations in neonatal open-heart surgery: a prospective observational study

Neonates with critical congenital heart defects undergoing open-heart surgery on cardiopulmonary bypass circulation are at risk for white matter brain injury. This article reports on pre- and postoperative plasma concentrations of brain injury markers glial fibrillary acidic protein (GFAP), neurofilament light (NfL) and Tau, and their respective associations with white matter lesions detected on postoperatively performed brain MRI. Forty term newborns with isolated critical congenital heart defects were included in a prospective observational study. Brain injury marker plasma concentrations were determined prior to surgery and at postoperative days 1, 2 and 3. Brain magnetic resonance imaging was performed pre- and postoperatively. Concentrations of brain injury markers were analysed using ultrasensitive single molecule array technology. Absolute pre- and postoperative plasma biomarker concentrations, and postoperative concentrations adjusted for preoperative concentrations were used for subsequent analysis. Plasma concentrations of GFAP, NfL and Tau displayed a well-defined temporal trajectory after neonatal cardiopulmonary bypass circulation. GFAP and Tau reached peak concentrations at postoperative day 2 (median concentrations 170.5 and 67.2 pg/ml, respectively), whereas NfL continued to increase throughout the study period (median concentration at postoperative day 3 191.5 pg/ml). Adjusted Tau at postoperative day 2 was significantly higher in infants presenting with white matter lesions on postoperative MRI compared to infants without white matter injury.

Central role of laboratory medicine in public health and patient care

Clinical laboratories play a vital role in the healthcare system. Objective medical data provided by clinical laboratories supports approximately 60-70% of clinical decisions, however, evidence supporting this claim is poorly documented and laboratories still lack visibility, despite their indisputable impact on patient care and public health. The International Federation for Clinical Chemistry and Laboratory Medicine (IFCC) Task Force on Outcome Studies in Laboratory Medicine (TF-OSLM) was recently developed to support directed research evaluating the role of laboratory medicine on clinical outcomes. Establishing and documenting this evidence is key to enhance visibility of the field in the eye of the public and other healthcare professionals together with optimizing patient outcomes and health care system operations. In this review, we discuss four areas that exemplify the contribution of laboratory medicine directly to patient care. This includes high-sensitivity cardiac troponin (hs-cTn) and N-terminal pro-B-type natriuretic peptide/B-type natriuretic peptides (NT-proBNP/BNP) for the diagnosis and prognosis of myocardial infarction and heart failure, respectively, and procalcitonin for the management of sepsis and antibiotic stewardship. Emerging markers of traumatic brain injury and the role of laboratory medicine in the fight against the COVID-19 pandemic are discussed along with an introduction to plans of IFCC TF-OSLM.

Abusive Head Trauma Animal Models: Focus on Biomarkers

Abusive head trauma (AHT) is a serious traumatic brain injury and the leading cause of death in children younger than 2 years. The development of experimental animal models to simulate clinical AHT cases is challenging. Several animal models have been designed to mimic the pathophysiological and behavioral changes in pediatric AHT, ranging from lissencephalic rodents to gyrencephalic piglets, lambs, and non-human primates. These models can provide helpful information for AHT, but many studies utilizing them lack consistent and rigorous characterization of brain changes and have low reproducibility of the inflicted trauma. Clinical translatability of animal models is also limited due to significant structural differences between developing infant human brains and the brains of animals, and an insufficient ability to mimic the effects of long-term degenerative diseases and to model how secondary injuries impact the development of the brain in children. Nevertheless, animal models can provide clues on biochemical effectors that mediate secondary brain injury after AHT including neuroinflammation, excitotoxicity, reactive oxygen toxicity, axonal damage, and neuronal death. They also allow for investigation of the interdependency of injured neurons and analysis of the cell types involved in neuronal degeneration and malfunction. This review first focuses on the clinical challenges in diagnosing AHT and describes various biomarkers in clinical AHT cases. Then typical preclinical biomarkers such as microglia and astrocytes, reactive oxygen species, and activated N-methyl-D-aspartate receptors in AHT are described, and the value and limitations of animal models in preclinical drug discovery for AHT are discussed.

Blood biomarkers of secondary outcomes following concussion: A systematic review

Introduction

Blood biomarkers have been identified as an alternative tool for predicting secondary outcomes following concussion. This systematic review aimed to summarize the literature on blood biomarkers of secondary outcomes following concussion in both pediatric and adult cohorts.

Methods

A literature search of Embase, Medline and PubMed was conducted. Two reviewers independently assessed retrieved studies to determine inclusion in systematic review synthesis.

Results

A total of 1771 unique studies were retrieved, 58 of which were included in the final synthesis. S100B, GFAP and tau were identified as being associated with secondary outcomes following concussion. Seventeen percent of studies were performed in a solely pediatric setting.

Conclusions

Validation of biomarkers associated with secondary outcomes following concussion have been largely limited by heterogeneous study cohorts and definitions of concussion and mTBI, presenting a hurdle for translation of these markers into clinical practice. Additionally, there was an underrepresentation of studies which investigated pediatric cohorts. Adult markers are not appropriate for children, therefore pediatric specific markers of secondary outcomes following concussion present the biggest gap in this field.

Examining four blood biomarkers for the detection of acute intracranial abnormalities following mild traumatic brain injury in older adults

Blood-based biomarkers have been increasingly studied for diagnostic and prognostic purposes in patients with mild traumatic brain injury (MTBI). Biomarker levels in blood have been shown to vary throughout age groups. Our aim was to study four blood biomarkers, glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase-L1 (UCH-L1), neurofilament light (NF-L), and total tau (t-tau), in older adult patients with MTBI. The study sample was collected in the emergency department in Tampere University Hospital, Finland, between November 2015 and November 2016. All consecutive adult patients with head injury were eligible for inclusion. Serum samples were collected from the enrolled patients, which were frozen and later sent for biomarker analyses. Patients aged 60 years or older with MTBI, head computed tomography (CT) imaging, and available biomarker levels were eligible for this study. A total of 83 patients (mean age = 79.0, SD = 9.58, range = 60-100; 41.0% men) were included in the analysis. GFAP was the only biomarker to show statistically significant differentiation between patients with and without acute head CT abnormalities [U₍₈₃₎ = 280, p < 0.001, r = 0.44; area under the curve (AUC) = 0.79, 95% CI = 0.67-0.91]. The median UCH-L1 values were modestly greater in the abnormal head CT group vs. normal head CT group [U ₍₈₃₎ = 492, p = 0.065, r = 0.20; AUC = 0.63, 95% CI = 0.49-0.77]. Older age was associated with biomarker levels in the normal head CT group, with the most prominent age associations being with NF-L (r = 0.56) and GFAP (r = 0.54). The results support the use of GFAP in detecting abnormal head CT findings in older adults with MTBIs. However, small sample sizes run the risk for producing non-replicable findings that may not generalize to the population and do not translate well to clinical use. Further studies should consider the potential effect of age on biomarker levels when establishing clinical cut-off values for detecting head CT abnormalities.

Pediatric Traumatic Brain Injury: An Update on Preclinical Models, Clinical Biomarkers, and the Implications of Cerebrovascular Dysfunction

Traumatic brain injury (TBI) is a leading cause of pediatric morbidity and mortality. Recent studies suggest that children and adolescents have worse post-TBI outcomes and take longer to recover than adults. However, the pathophysiology and progression of TBI in the pediatric population are studied to a far lesser extent compared to the adult population. Common causes of TBI in children are falls, sports/recreation-related injuries, non-accidental trauma, and motor vehicle-related injuries. A fundamental understanding of TBI pathophysiology is crucial in preventing long-term brain injury sequelae. Animal models of TBI have played an essential role in addressing the knowledge gaps relating to pTBI pathophysiology. Moreover, a better understanding of clinical biomarkers is crucial to diagnose pTBI and accurately predict long-term outcomes. This review examines the current preclinical models of pTBI, the implications of pTBI on the brain’s vasculature, and clinical pTBI biomarkers. Finally, we conclude the review by speculating on the emerging role of the gut-brain axis in pTBI pathophysiology.

Biomarkers in Moderate to Severe Pediatric Traumatic Brain Injury: A Review of the Literature

BACKGROUND

Despite decades of research, outcomes in pediatric traumatic brain injury (pTBI) remain highly variable. Brain biofluid-specific biomarkers from pTBI patients may allow us to diagnose and prognosticate earlier and with a greater degree of accuracy than conventional methods. This manuscript reviews the evidence surrounding current brain-specific biomarkers in pTBI and assesses the temporal relationship between the natural history of the traumatic brain injury (TBI) and measured biomarker levels.

METHODS

A literature search was conducted in the Ovid, PubMed, MEDLINE, and Cochrane databases seeking relevant publications. The study selection and screening process were documented in a Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram. Extraction forms included developmental stages of patients, type and biofluid source of biomarkers, brain injury type, and other relevant data.

RESULTS

The search strategy identified 443 articles, of which 150 examining the biomarkers of our interest were included. The references retrieved were examined thoroughly and discussed at length with a pediatric neurocritical care intensivist specializing in pTBI and a Ph.D. scientist with a high degree of involvement in TBI biomarker research, authoring a vast amount of literature in this field.

CONCLUSIONS

TBI biomarkers might serve as valuable tools in the diagnosis and prognosis of pTBI. However, while each biomarker has its advantages, they are not without limitations, and therefore, further research is critical in pTBI biomarkers.

Association of Plasma Tau With Mortality and Long-term Neurocognitive Impairment in Survivors of Pediatric Cerebral Malaria and Severe Malarial Anemia

IMPORTANCE

Cerebral malaria (CM) and severe malarial anemia (SMA) are associated with persistent neurocognitive impairment (NCI) among children in Africa. Identifying blood biomarkers of acute brain injury that are associated with future NCI could allow early interventions to prevent or reduce NCI in survivors of severe malaria.

OBJECTIVE

To investigate whether acutely elevated tau levels are associated with future NCI in children after CM or SMA.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study was conducted at Mulago National Referral Hospital in Kampala, Uganda, from March 2008 to October 2015. Children aged 1.5 to 12 years with CM (n = 182) or SMA (n = 162) as well as community children (CC; n = 123) were enrolled in the study. Data analysis was conducted from January 2020 to May 2021.

EXPOSURE

CM or SMA.

MAIN OUTCOMES AND MEASURES

Enrollment plasma tau levels were measured using single-molecule array detection technology. Overall cognition (primary) and attention and memory (secondary) z scores were measured at 1 week and 6, 12, and 24 months after discharge using tools validated in Ugandan children younger than 5 years or 5 years and older.

RESULTS

A total of 467 children were enrolled. In the CM group, 75 (41%) were girls, and the mean (SD) age was 4.02 (1.92) years. In the SMA group, 59 (36%) were girls, and the mean (SD) age was 3.45 (1.60) years. In the CC group, 65 (53%) were girls, and the mean (SD) age was 3.94 (1.92) years. Elevated plasma tau levels (>95th percentile in CC group; >6.43 pg/mL) were observed in 100 children (55%) with CM and 69 children (43%) with SMA (P < .001). In children with CM who were younger than 5 years, elevated plasma tau levels were associated with increased mortality (odds ratio [OR], 3.06; 95% CI, 1.01-9.26; P = .048). In children with CM who were younger than 5 years at both CM episode and follow-up neurocognitive testing, plasma tau levels (log10 transformed) were associated with worse overall cognition scores over 24-month follow-up (β = -0.80; 95% CI, -1.32 to -0.27; P = .003). In children with CM who were younger than 5 years at CM episode and 5 years or older at follow-up neurocognitive testing, plasma tau was associated with worse scores in attention (β = -1.08; 95% CI, -1.79 to -0.38; P = .003) and working memory (β = -1.39; 95% CI, -2.18 to -0.60; P = .001).

CONCLUSIONS AND RELEVANCE

In this study, plasma tau, a marker of injury to neuronal axons, was elevated in children with CM or SMA and was associated with mortality and persistent NCI in children with CM younger than 5 years.

Blood-based traumatic brain injury biomarkers - Clinical utilities and regulatory pathways in the United States, Europe and Canada

INTRODUCTION

Traumatic brain injury (TBI) is a major global health issue, resulting in debilitating consequences to families, communities, and health-care systems. Prior research has found that biomarkers aid in the pathophysiological characterization and diagnosis of TBI. Significantly, the FDA has recently cleared both a bench-top assay and a rapid point-of-care assays of tandem biomarker (UCH-L1/GFAP)-based blood test to aid in the diagnosis mTBI patients. With the global necessity of TBI biomarkers research, several major consortium multicenter observational studies with biosample collection and biomarker analysis have been created in the USA, Europe, and Canada. As each geographical region regulates its data and findings, the International Initiative for Traumatic Brain Injury Research (InTBIR) was formed to facilitate data integration and dissemination across these consortia.

AREAS COVERED

This paper covers heavily investigated TBI biomarkers and emerging non-protein markers. Finally, we analyze the regulatory pathways for converting promising TBI biomarkers into approved in-vitro diagnostic tests in the United States, European Union, and Canada.

EXPERT OPINION

TBI biomarker research has significantly advanced in the last decade. The recent approval of an iSTAT point of care test to detect mild TBI has paved the way for future biomarker clearance and appropriate clinical use across the globe.

Serum biomarkers in severe paediatric traumatic brain injury-a narrative review

Severe traumatic brain injury continues to present complex management and prediction challenges for the clinician. While there is some evidence that better systems of care can improve outcome, multiple multi-centre randomised controlled trials of specific therapies have consistently failed to show benefit. In addition, clinicians are challenged in attempting to accurately predict which children will recover well and which children will have severe and persisting neurocognitive deficits. Traumatic brain injury is vastly heterogeneous and so it is not surprising that one therapy or approach, when applied to a mixed cohort of children in a clinical trial setting, has yielded disappointing results. Children with severe traumatic brain injury have vastly different brain injury pathologies of widely varying severity, in any number of anatomical locations at what may be disparate stages of brain development. This heterogeneity may also explain why clinicians are unable to accurately predict outcome. Biomarkers are objective molecular signatures of injury that are released following traumatic brain injury and may represent a way of unifying the heterogeneity of traumatic brain injury into a single biosignature. Biomarkers hold promise to diagnose brain injury severity, guide intervention selection for clinical trials, or provide vital prognostic information so that early intervention and rehabilitation can be planned much earlier in the course of a child's recovery. Serum S100B and serum NSE levels show promise as a diagnostic tool with biomarker levels significantly higher in children with severe TBI including children with inflicted and non-inflicted head injury. Serum S100B and serum NSE also show promise as a predictor of neurodevelopmental outcome. The role of biomarkers in traumatic brain injury is an evolving field with the potential for clinical application within the next few years.

Traumatic brain injury biomarkers in pediatric patients: a systematic review

Traumatic brain injury (TBI) is the main cause of pediatric trauma death and disability worldwide. Recent studies have sought to identify biomarkers of TBI for the purpose of assessing functional outcomes. The aim of this systematic review was to evaluate the utility of TBI biomarkers in the pediatric population by summarizing recent findings in the medical literature. A total of 303 articles were retrieved from our search. An initial screening to remove duplicate studies yielded 162 articles. After excluding all articles that did not meet the inclusion criteria, 56 studies were gathered. Among the 56 studies, 36 analyzed serum biomarkers; 11, neuroimaging biomarkers; and 9, cerebrospinal fluid (CSF) biomarkers. Most studies assessed biomarkers in the serum, reflecting the feasibility of obtaining blood samples compared to obtaining CSF or performing neuroimaging. S100B was the most studied serum biomarker in TBI, followed by SNE and UCH-L1, whereas in CSF analysis, there was no unanimity. Among the different neuroimaging techniques employed, diffusion tensor imaging (DTI) was the most common, seemingly holding diagnostic power in the pediatric TBI clinical setting. The number of cross-sectional studies was similar to the number of longitudinal studies. Our data suggest that S100B measurement has high sensitivity and great promise in diagnosing pediatric TBI, ideally when associated with head CT examination and clinical decision protocols. Further large-scale longitudinal studies addressing TBI biomarkers in children are required to establish more accurate diagnostic protocols and prognostic tools.

Serum levels of total human Tau associated with axonal damage among severe malaria patients in Central India

Tau is a microtubule-associated protein (MAP) that is abundant in the axonal part of neurons of the central nervous system. Previous studies among African children and Vietnamese adults suffering from cerebral malaria (CM) showed the pathological significance of measuring circulatory total Tau levels. A pilot investigation was carried out to better characterise neurological pathogenesis among severe malaria patients in Central India. Serum levels of total human Tau (pg/ml) were measured by ELISA following manufacturer guidelines among hospital admitted P. falciparum malaria patients classified with different degree of severity (mild malaria = MM, non-cerebral severe malaria = NCSM, cerebral malaria survivors = CM-S and cerebral malaria non-survivors = CM-NS) using WHO, 2000 definitions, including healthy controls (HC) enroled from the hospital's blood bank. Categorical and numerical variables were analysed by applying appropriate statistical test using Stata 11.0 software. A total of 139 subjects (14 HC, 25 MM, 29 NCSM, 44 CM-S and 27 CM-NS) were included in this preliminary investigation. Serum levels of total human Tau were detected in 0% HC, 4.0% MM, 20.7% NCSM, 43.2% CM-S and 48.2% CM-NS patients. Compared to MM, percent Tau detection was significantly higher among severe malaria patients (p = 0.001). Further, compared to NCSM,% Tau detection was significantly higher in CM-S patients (Chi² = 3.9, p = 0.048) & CM-NS patients (Chi² = 4.7, p = 0.030). Percent Tau detection was also significantly higher among severe malaria cases presenting with multiple complications compared to those without multiple complications (p = 0.006). ROC analysis of serum Tau levels (pg/ml) revealed a fair AUC value (0.75) to distinguish CM-NS group (but not CM-S) from NCSM group. In conclusion, serum percent detection of total human Tau is associated with axonal damage among patients with different degree of P. falciparum malaria severity in Central India.

Effects of acute sleep loss on diurnal plasma dynamics of CNS health biomarkers in young men

Objective

Disrupted sleep increases CSF levels of tau and β-amyloid (Aβ) and is associated with an increased risk of Alzheimer disease (AD). Our aim was to determine whether acute sleep loss alters diurnal profiles of plasma-based AD-associated biomarkers.

Methods

In a 2-condition crossover study, 15 healthy young men participated in 2 standardized sedentary in-laboratory conditions in randomized order: normal sleep vs overnight sleep loss. Plasma levels of total tau (t-tau), Aβ40, Aβ42, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) were assessed using ultrasensitive single molecule array assays or ELISAs, in the fasted state in the evening prior to, and in the morning after, each intervention.

Results

In response to sleep loss (+17.2%), compared with normal sleep (+1.8%), the evening to morning ratio was increased for t-tau (p = 0.035). No changes between the sleep conditions were seen for levels of Aβ40, Aβ42, NfL, or GFAP (all p > 0.10). The AD risk genotype rs4420638 did not significantly interact with sleep loss–related diurnal changes in plasma levels of Aβ40 or Aβ42 (p > 0.10). Plasma levels of Aβ42 (−17.1%) and GFAP (−12.1%) exhibited an evening to morning decrease across conditions (p < 0.05).

Conclusions

Our exploratory study suggests that acute sleep loss results in increased blood levels of t-tau. These changes provide further evidence that sleep loss may have detrimental effects on brain health even in younger individuals. Larger cohorts are warranted to delineate sleep vs circadian mechanisms, implications for long-term recurrent conditions (e.g., in shift workers), as well as interactions with other lifestyle and genetic factors.

Increased severity of the CHIMERA model induces acute vascular injury, sub-acute deficits in memory recall, and chronic white matter gliosis

Traumatic brain injury (TBI) is a leading cause of death and disability in modern societies. Diffuse axonal and vascular injury are nearly universal consequences of mechanical energy impacting the head and contribute to disability throughout the injury severity spectrum. CHIMERA (Closed Head Impact Model of Engineered Rotational Acceleration) is a non-surgical, impact-acceleration model of rodent TBI that reliably produces diffuse axonal injury characterized by white matter gliosis and axonal damage. At impact energies up to 0.7 joules, which result in mild TBI in mice, CHIMERA does not produce detectable vascular or grey matter injury. This study was designed to expand CHIMERA's capacity to induce more severe injuries, including vascular damage and grey matter gliosis. This was made possible by designing a physical interface positioned between the piston and animal's head to allow higher impact energies to be transmitted to the head without causing skull fracture. Here, we assessed interface-assisted single CHIMERA TBI at 2.5 joules in wild-type mice using a study design that spanned 6 h-60 d time points. Injured animals displayed robust acute neurological deficits, elevated plasma total tau and neurofilament-light levels, transiently increased proinflammatory cytokines in brain tissue, blood-brain barrier (BBB) leakage and microstructural vascular abnormalities, and grey matter microgliosis. Memory deficits were evident at 30 d and resolved by 60 d. Intriguingly, white matter injury was not remarkable at acute time points but evolved over time, with white matter gliosis being most extensive at 60 d. Interface-assisted CHIMERA thus enables experimental modeling of distinct endophenotypes of TBI that include acute vascular and grey matter injury in addition to chronic evolution of white matter damage, similar to the natural history of human TBI.