Edited by: Firas H. Kobeissy, University of Florida, USA
Reviewed by: Alana Conti, Wayne State University, USA; Ayman K. Hamouda, Texas A&M Health Science Center, USA; Massoud Louis Khraiche, University of California San Diego, USA
Specialty section: This article was submitted to Neurotrauma, a section of the journal Frontiers in Neurology
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Blood biomarkers are valuable tools for elucidating complex cellular and molecular mechanisms underlying traumatic brain injury (TBI). Profiling distinct classes of biomarkers could aid in the identification and characterization of initial injury and secondary pathological processes. This study characterized the prognostic performance of a recently developed multi-marker panel of circulating biomarkers that reflect specific pathogenic mechanisms including neuroinflammation, oxidative damage, and neuroregeneration, in moderate-to-severe TBI patients.
Peripheral blood was drawn from 85 isolated TBI patients (
Unfavorable neurological outcome was associated with elevations in s100B, GFAP, and MCP-1. Mortality was related to differences in six of the seven markers analyzed. Combined admission concentrations of s100B, GFAP, and MCP-1 were able to discriminate favorable versus unfavorable outcome (AUC = 0.83), and survival versus death (AUC = 0.87), although not significantly better than s100B alone (AUC = 0.82 and 0.86, respectively).
The multi-marker panel of TBI-related biomarkers performed well in discriminating unfavorable and favorable outcomes in the acute period after moderate-to-severe TBI. However, the combination of these biomarkers did not outperform s100B alone.
The multifactorial nature of secondary injury after traumatic brain injury (TBI), especially the complex networks of molecular pathways mediating cellular damage in different brain regions, has confounded attempts to elucidate the pathology underlying injury progression (
The peripheral blood can be used as a source of biomarkers indicative of neuropathology across the spectrum of mild to severe brain injury (
Several blood-borne biomarker candidates have been investigated either individually or collectively across the spectrum of TBI severity. In particular, s100 calcium binding protein beta (s100B) and neuron specific enolase (NSE) have been widely studied, and elevated circulating concentrations of these markers may be associated with secondary injury progression (
Thus, a multi-marker approach to characterizing TBI outcome has been advocated, since the simultaneous estimation of multiple markers to establish a “biological signature” may prove more effective in encompassing the multisystemic character of secondary injury pathology, and may increase diagnostic and prognostic accuracy (
Hence, the purpose of this study was to further examine a recently developed panel of 7 biomarkers in a cohort of moderate-to-severe TBI patients. The two specific aims were (1) to characterize the temporal profile of plasma s100B, GFAP, NSE, BDNF, MCP-1, ICAM-5, and PRDX-6 concentrations at four time-points within the first 24 h of hospital admission, stratified according to patient outcomes, (2) to compare the individual and collective utility of these markers in discriminating between favorable and unfavorable patient outcomes.
Potential study participants were admitted to Sunnybrook Health Sciences Centre and St. Michael’s Hospital (Toronto, ON, Canada). Upon admission, the trauma team/emergency room personnel enrolled patients who met the initial criteria of sustaining an isolated TBI, defined by a Glasgow Coma Score of <13 and a non-head abbreviated injury score (AIS) ≤2; TBI patients were further dichotomized into moderate (GCS 9–12) and severe (GCS 3–8) injury. Consent for enrollment was obtained from a substitute decision maker. If this was not possible, consent was delayed in accordance with the Tri-Council Policy Agreement for Research in Emergency Health Situations (Article 2.8), and obtained from next-of-kin. If the patient recovered sufficiently to provide consent, their consent was also obtained. Patients were excluded in the following cases: an elapsed time between trauma and hospital admission in excess of 3 h, <16 years of age, pregnant, lacking vital signs prior to admission, or clinically brain dead on admission. The study protocol was approved by the Research Ethics Boards at Sunnybrook Health Sciences Centre and St. Michaels Hospital. Blood samples were drawn from healthy volunteers after obtaining written informed consent in accordance with the principles of the Declaration of Helsinki.
At hospital admission, demographic data were obtained from study patients along with a number of clinical indices. This process has been described in detail previously (
Venous blood samples were collected at hospital admission, and then again at 6-, 12-, and 24-h post-injury. Samples were drawn into 10-ml K2EDTA (with 4 mM sodium metabisulfite [Na2S2O5]) or 10-ml sodium heparin vacutainers (Vacutainer, Becton Dickinson, Rutherford, NJ, USA). The samples were immediately centrifuged at 1600 ×
Clinical and demographic data are represented as the mean ± SD unless otherwise noted. The normality of each variable was assessed before the appropriate statistical test was applied. To examine 6-month neurological outcome, patients were dichotomized into favorable (GOSE 5–8) and unfavorable (GOSE 1–4) outcome groups. Similarly, patients were also stratified into two groups, “Lived” and “Died” to assess mortality. Group classifications for both neurological outcome and mortality were analyzed at each time-point using either a Student’s
Clinical and demographic data for all TBI patients are described in Table
Characteristics | All patients ( |
Moderate TBI ( |
Severe TBI ( |
---|---|---|---|
Age (years) | 45.8 ± 21.9 | 47.9 ± 21.7 | 44.9 ± 22.2 |
Male gender – |
66 (77.6) | 19 (76.0) | 47 (78.3) |
Trauma type – |
|||
Blunt | 83 (97.6) | 24 (96.0) | 59 (98.3) |
Penetrating | 2 (2.3) | 1 (4.0) | 1 (1.7) |
Time to ED (min) | 79.6 ± 56.4 | 72.3 ± 52.0 | 82.7 ± 58.2 |
ISS score | 23.6 ± 11.0 | 19.1 ± 12.5 | 25.4 ± 9.8 |
AIS head | 4.2 ± 1.1 | 3.6 ± 1.2 | 4.4 ± 1.0 |
GCS | 6.5 ± 3.3 | 10.8 ± 1.2 | 4.63 ± 2.0 |
Positive CT – |
70 (82.3) | 18 (72.0) | 52 (86.7) |
Positive serum ethanol – |
27 (31.8) | 10 (40.0) | 17 (31.7) |
Pre-injury comorbidities – |
27 (31.8) | 11 (44.0) | 16 (26.7) |
Pre-injury beta-blocker use – |
4 (4.7) | 1 (4.0) | 3 (5.0) |
Neurosurgical intervention – |
25 (29.4) | 3 (12.0) | 22 (36.7) |
Mortality |
24 (28.2) | – | 24 (40.0) |
Unfavorable outcome – |
50 (58.8) | 8 (32.0) | 42 (70.0) |
Sepsis infection – |
20 (23.5) | 6 (24.0) | 14 (23.3) |
Organ failure – |
12 (14.1) | – | 12 (20.0) |
Significant differences in three of the seven markers were identified in patients with unfavorable versus favorable 6-month neurological outcome (Figures
Six of the seven neuroinjury markers were significantly different between survivors and non-survivors (Figures
See Table
Marker | Unfavorable outcome | Mortality |
---|---|---|
s100B | 82.5 ± 0.05 |
86.5 ± 0.04 |
GFAP | 71.5 ± 0.06 |
79.5 ± 0.06 |
NSE | 59.5 ± 0.06 | 61.3 ± 0.07 |
BDNF | 48.5 ± 0.07 | 47.8 ± 0.08 |
MCP-1 | 65.3 ± 0.06 |
70.2 ± 0.06 |
ICAM-5 | 46.4 ± 0.07 | 62.4 ± 0.07 |
PRDX-6 | 48.6 ± 0.07 | 56.1 ± 0.07 |
Multivariate models were created using the significant individual predictors of unfavorable 6-month neurological outcome and mortality to create multi-marker ROC curves. This model, which consisted of s100B, GFAP, and MCP-1, did not significantly differ from s100B alone in discriminating favorable from unfavorable outcome (AUC = 0.83 versus AUC = 0.82) (Figure
This study characterized peripheral blood s100B, GFAP, NSE, BDNF, MCP-1, ICAM-5, and PRDX-6 levels over the first 24 h post-hospital admission in 85 moderate-to-severe TBI patients. We identified significantly elevated concentrations of s100B and GFAP at all sample time points (admission, 6-, 12-, 24-h) in patients with unfavorable neurological outcome at 6 months and in those who died. This is in agreement with previous studies that found high levels of s100B and GFAP were associated with poor outcome at 1–6 months post-TBI. While we found no relationship between NSE and 6-month neurological outcome, mortality was associated with elevations of NSE at 6 h after hospital admission. Our results are in accord with prior findings that identified a relationship between blood NSE levels early after injury, and mortality (
Both CNS and systemic inflammation are critical components to secondary injury after TBI (
Secondary injury after TBI not only encompasses damage-related processes that worsen brain injury, but also an altered state of tissue regeneration and repair (
In the current study, a multiple-marker model consisting of s100B, GFAP, and MCP-1 did not yield significantly higher AUC values for discriminating unfavorable from favorable outcomes after TBI compared to s100B alone. Previous TBI studies that have characterized biomarkers in relation to patient outcomes have often evaluated markers individually (
Despite having a robust sample size to characterize TBI, a larger patient cohort would have been required for further sub-stratifications, particularly to dichotomize moderate and severe patients; we were unable to assess outcome and mortality in isolated severe and moderate injures due to a lack of moderately injured patients with unfavorable outcomes. Future studies should also consider incorporating multiple-marker panels relating biological molecules to brain-specific clinical indices such as intracranial pressure and specific CT scan classifications, as well as associated systemic outcomes of TBI including sepsis and multiple organ failure.
Traumatic brain injury elicits the release of a number of neuroinjury molecules that are easily assessed in the peripheral blood and hold promise in the clinical management of patients. In the present study, elevated levels of s100B, GFAP, and MCP-1 in the peripheral blood of TBI patients within 24 h of hospital admission were associated with both unfavorable 6-month neurological outcome and death. Despite promising evidence of multi-marker algorithms displaying enhanced utility to discriminate between healthy individuals and TBI patients, under the current approach, the combination of each individual marker did not yield greater integrated discrimination beyond the single-marker s100B in moderate-to-severe TBI.
All authors were involved in the drafting and revising of the manuscript, as well as the interpretation of the data. JB, GM, RD-A, SR, AB, and SR all contributed substantially to the conception and design of this work. AD, MH, JB, GM, and SR contributed substantially to the acquisition and analysis of the data.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The authors gratefully acknowledge the technical assistance of Ms. Maria Shiu and Mr. Shahid Hassan. This research was funded by the Defence Research and Development Canada Technology Investment Fund Programme, the Center for Neuroscience and Regenerative Medicine, and the Tri-Service Nursing Research Program, Grant #HT9404-12-1-TS13.