Plasma and Salivary S100B in the Prognosis of Vital Status and Functional Dependence in Patients with Blunt Traumatic Brain Injury

Plasma and Salivary S100B in the Prognosis of Vital Status and Functional Dependence in Patients with Blunt Traumatic Brain Injury | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 20 October 2025 V1 Latest version Share on Plasma and Salivary S100B in the Prognosis of Vital Status and Functional Dependence in Patients with Blunt Traumatic Brain Injury Authors : Thamires de Oliveira Rocha 0009-0009-9618-3836 [email protected] , Lillian Caroline Fernandes , Dyenilly Alessi Sloboda , Leda Talib 0000-0001-5866-1993 , Wellingson Silva Paiva , Lilia de Souza Nogueira , and Regina Márcia Cardoso de Sousa Authors Info & Affiliations 161 views 91 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Objective: To evaluate plasma and salivary S100B for predicting death and functional dependence after blunt traumatic brain injury (TBI). Methods: Prospective cohort of 57 patients of blunt TBI (aged 18–59 years) was developed, with the head as the primary injury site, admitted for treatment within four hours post-trauma. Clinical data, blood, and saliva were collected at hospital admission, and vital status and functional capacity were assessed at hospital discharge and three months post-TBI. Results: The median concentrations of the S100B protein among participants were 17.50pg/mL in plasma and 5.73pg/mL in saliva; in both biofluids, protein levels were higher in patients who died or had unfavorable outcomes compared to the concentrations of survivors and those with favorable outcomes, both at hospital discharge and three months post-trauma. For death prediction, the area under the curve (AUC/ROC) was 0.84 (95%CI=0.69–0.99) and 0.77 (95%CI=0.66–0.89) for saliva and plasma, respectively, at hospital discharge; at three months, the values were 0.88 (95%CI=0.77–0.99) for saliva and 0.83 (95%CI=0.73–0.94) for plasma. Among survivors, S100B showed an AUC/ROC of 0.90 (95%CI=0.81–0.99) for saliva and 0.86 (95%CI=0.72–0.99) for plasma in predicting functional dependence at hospital discharge; at three months, the AUC/ROC was 0.84 (95%CI=0.72–0.96) and 0.89 (95%CI=0.75–1.00) for saliva and plasma, respectively. Interpretation: At hospital discharge and three months post-trauma, plasma and salivary S100B demonstrated good discriminative ability regarding vital status and functional dependence in patients of TBI. Plasma and Salivary S100B in the Prognosis of Vital Status and Functional Dependence in Patients with Blunt Traumatic Brain Injury Running head: Prognosis of S100B in Blunt TBI. First author Thamires de Oliveira Rocha (RN, M.Sc.)* a 419, Av. Doutor Enéas Carvalho de Aguiar, São Paulo, SP, Brasil, 05403-000. Telephone number: +55 11 3061-7533 [email protected] ORCID: 0009-0009-9618-3836 Co-authors Lillian Caroline Fernandes (RN, Ph.D.) b 419, Av. Doutor Enéas Carvalho de Aguiar, São Paulo, SP, Brasil, 05403-000. Telephone number: +55 11 3061-7544 [email protected] ORCID: 0000-0002-7557-5285 Dyenilly Alessi Sloboda (RN, Ph.D.) c 4748, Av. General Carlos Cavalcanti, Ponta Grossa, PR, Brasil, 84030-000. Telephone number: +55 42 3220-3735 [email protected] ORCID: 0000-0002-3019-1659 Leda Leme Talib (Pharm., Ph.D.) d 785. Av. Doutor Ovídio Pires de Campos, São Paulo, SP, Brasil, 05403-903. Telephone number: +55 11 2661-7283 [email protected] ORCID: 0000-0001-5866-1993 Wellingson Silva Paiva (MD, Ph.D.) e 255. Av. Doutor Enéas Carvalho de Aguiar. São Paulo, SP, Brasil, 05403-000. Telephone number: +55 11 2661-0000 [email protected] ORCID: 0000-0002-5165-7040 Lilia de Souza Nogueira (RN, Ph.D.) b 419, Av. Doutor Enéas Carvalho de Aguiar, São Paulo, SP, Brasil, 05403-000. Telephone number: +55 11 3061-7544 [email protected] ORCID: 0000-0001-5387-3807 Regina Márcia Cardoso de Sousa (RN, Ph.D.) b 419, Av. Doutor Enéas Carvalho de Aguiar, São Paulo, SP, Brasil, 05403-000. Telefone: +55 11 3061-7544 [email protected] ORCID: 0000-0002-2575-7937 Affiliations: a Programa Pós-Graduação de Enfermagem na Saúde do Adulto. Escola de Enfermagem da Universidade de São Paulo. Universidade de São Paulo. São Paulo, SP, Brasil. b Departamento de Enfermagem Médico-Cirúrgica. Escola de Enfermagem da Universidade de São Paulo. Universidade de São Paulo SP, Brasil. c Departamento de Enfermagem. Universidade Estadual de Ponta Grossa. Ponta Grossa, PR, Brasil. d Laboratório de Investigação Médica 27 (LIM-27). Instituto de Psiquiatria do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Universidade de São Paulo. São Paulo, SP, Brasil. e Divisão de Neurocirurgia. Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Universidade de São Paulo, São Paulo, SP, Brasil. * Corresponding author: Thamires de Oliveira Rocha. Programa Pós-Graduação de Enfermagem na Saúde do Adulto, Escola de Enfermagem da Universidade de São Paulo, Universidade de São Paulo. 419, Av. Doutor Enéas Carvalho de Aguiar, São Paulo, SP, Brasil, 05403-000. Telephone number: +55 11 3061-7533. E-mail: [email protected] Acknowledgments The authors thank the Coordination for the Improvement of Higher Education Personnel (CAPES) for funding the study; the School of Nursing (EEUSP) and the Faculty of Medicine of the University of São Paulo (FMUSP) for support in data collection and study development; the Medical Investigation Laboratory (LIM-27) of FMUSP for support with the laboratory analyses of this investigation; and the statistics services of EEUSP for the analyses performed. Plasma and Salivary S100B in the Prognosis of Vital Status and Functional Dependence in Patients with Blunt Traumatic Brain Injury Objective: To evaluate plasma and salivary S100B for predicting death and functional dependence after blunt traumatic brain injury (TBI). Methods: Prospective cohort of 57 patients of blunt TBI (aged 18–59 years) was developed, with the head as the primary injury site, admitted for treatment within four hours post-trauma. Clinical data, blood, and saliva were collected at hospital admission, and vital status and functional capacity were assessed at hospital discharge and three months post-TBI. Results: The median concentrations of the S100B protein among participants were 17.50pg/mL in plasma and 5.73pg/mL in saliva; in both biofluids, protein levels were higher in patients who died or had unfavorable outcomes compared to the concentrations of survivors and those with favorable outcomes, both at hospital discharge and three months post-trauma. For death prediction, the area under the curve (AUC/ROC) was 0.84 (95%CI=0.69–0.99) and 0.77 (95%CI=0.66–0.89) for saliva and plasma, respectively, at hospital discharge; at three months, the values were 0.88 (95%CI=0.77–0.99) for saliva and 0.83 (95%CI=0.73–0.94) for plasma. Among survivors, S100B showed an AUC/ROC of 0.90 (95%CI=0.81–0.99) for saliva and 0.86 (95%CI=0.72–0.99) for plasma in predicting functional dependence at hospital discharge; at three months, the AUC/ROC was 0.84 (95%CI=0.72–0.96) and 0.89 (95%CI=0.75–1.00) for saliva and plasma, respectively. Interpretation: At hospital discharge and three months post-trauma, plasma and salivary S100B demonstrated good discriminative ability regarding vital status and functional dependence in patients of TBI. Keywords: Brain Injuries, Traumatic; Biomarkers; S100 Calcium Binding Protein beta Subunit; Prognosis; Saliva Introduction Traumatic brain injury (TBI) is a major global public health issue, affecting more than 60 million people annually. It is recognized as the leading cause of death and long-term functional disability among young adults, most commonly resulting from falls and traffic accidents 1-3 . TBI results from an external physical force that can cause both anatomical brain damage and functional impairment 4 . Approximately 16.7% of patients treated in healthcare facilities after TBI die 5 , and survivors often present functional impairments that range from subtle cognitive changes in mild cases to dependency requiring continuous rehabilitation in moderate and severe trauma 6,7 . Given the heterogeneous and frequently unfavorable post-trauma outcomes, the search for tools that allow early prognostic assessment of TBI patients has intensified. Prognostic estimation supports therapeutic decision-making by identifying patients whose progression deviates from the expected course. In addition, it enables the anticipation of healthcare resources, evaluation of care quality, and guidance for rehabilitation programs 8-10 . Functional assessment at hospital discharge provides a baseline measure of the patient’s condition at the time of reintegration into the community, offering valuable information for the support network involved in recovery 11-13 . Likewise, evaluating recovery at three months post-trauma is a critical component of TBI outcome studies 14 , since improvement occurs over a variable period, with significant gains usually observed within the first three months 15 . In this context, brain injury biomarkers present in various biofluids have gained attention as objective tools for predicting TBI outcomes 16,17 . Among brain injury biomarkers, the S100B protein has been the most studied. This glial calcium-binding protein is released after TBI, with serum levels correlating with brain contusion volumes 10,18,19 . S100B was able to stratify patients by injury severity, with low blood concentrations in mild TBI and increasing levels in moderate and severe trauma 10,20 , in addition to indicating the presence of Diffuse Axonal Injury, often not identified by imaging diagnostic methods 21 . Beyond its high diagnostic value, the protein has also proven to be a predictor of mortality and functional capacity after brain injury, especially in moderate and severe trauma 10,22-24 . A recent study highlighted the use of biomarkers as one of the pillars of a new proposal for the characterization of acute traumatic brain injuries 25 . S100B has a low molecular weight (9–13 kDa), which allows it to cross the blood–brain barrier and be detected in multiple biofluids, including cerebrospinal fluid, blood, urine, and saliva. Saliva is a more sustainable matrix that, through a simple, cost-effective, safe, and non-invasive collection, provides quantitative information on post-trauma intracranial conditions of different severities, as well as predicting possible outcomes in more severe trauma cases 21, 26-28 . Despite its potential, research on salivary S100B remains incipient, and its prognostic performance compared with plasma concentrations has not been fully established. Therefore, the present study aimed to evaluate the prognostic performance of S100B concentrations in plasma and saliva of patients with blunt TBI for predicting mortality and functional dependency at hospital discharge and three months post-trauma. Materials and Methods Study Design This was a prospective cohort study, that followed patients with blunt TBI from hospital admission to three months post-trauma. The study was conducted and reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines, according the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) Network. Study Location Data collection was carried out in four hospital institutions recognized for their expertise in trauma and TBI management, all of which operate under Advanced Trauma Life Support protocols. One institution functions as a reference center for trauma care within the private healthcare network, while the other study sites are teaching hospitals in Brazil’s public healthcare system, including one that serves as a referral center for high-complexity care. Participants A total of 57 patients with blunt TBI were recruited based on a history of head trauma at the time of hospital admission. Eligible participants were admitted to one of the study institutions within four hours after the traumatic event, were between 18 and 59 years of age, and had blunt head trauma as the main injury, classified according to the Abbreviated Injury Scale (AIS), a coding system of the Association for the Advancement of Automotive Medicine that categorizes traumatic injury severity from one (mild) to six (fatal). Exclusion criteria included extracranial injuries with an AIS score ≥ 3, a history of psychiatric disorders, neurological diseases, or previous TBI, as well as any pre-existing functional disability. Patients were categorized into three groups according to injury severity. To determine TBI severity, the Glasgow Coma Scale (GCS) score at hospital admission was considered, except for patients intubated during Pre-Hospital Care, for whom the GCS score measured prior to orotracheal intubation was used. Patients were classified as having mild TBI when the GCS score was 13–15, moderate TBI with a score of 9–12, and severe TBI when the score was ≤ 8. Data Collection Sociodemographic and clinical data were obtained from medical records and supplemented through interviews with patients, family caregivers, or healthcare staff at the study sites. Blood and saliva samples were collected between the second and fourth hour after trauma. Blood samples were obtained by venipuncture using a 23-gauge Scalp® needle and stored in heparinized tubes. Saliva was collected using a Salivette® cotton roll, placed in the oral cavity either directly or with the aid of tweezers, positioned between the teeth and the lateral oral mucosa for ten minutes. Samples were stored at 2–8°C for up to 24 hours, centrifuged at 3000 rpm for 15 minutes at 4°C, and then frozen at –80°C. Plasma and saliva samples were analyzed within three months of collection and the determinations of S100B concentrations was performed using the S100 Calcium Binding Protein B (S100B) Enzyme-Linked Immunosorbent Assay (ELISA) Kit, Lot (5JSK3G266P) from MyBioSource, USA, sensibility: 18 pg/mL. All procedures followed the manufacturer’s instructions (MyBioSource® Manual) 29 , and each sample was analyzed in duplicate. The mean of the two measurements was used as the final S100B concentration. Functional capacity was assessed at hospital discharge using the Glasgow Outcome at Discharge Scale (GODS), in collaboration with the nurse responsible for patient care. At three months post-injury, functional outcomes were evaluated with the Glasgow Outcome Scale–Extended (GOSE), administered either by telephone with the patient or caregiver or in person during outpatient follow-up. The use of these instruments was exclusively for research purposes and was not part of routine institutional protocols. Accordingly, the GODS and GOSE assessments were performed by two trained members of the research team. Prior to data collection, training sessions were conducted to standardize the administration of the instruments and the interview approach. This training took place in person at the study sites, under the supervision of an experienced researcher, who also provided ongoing guidance and clarification of any questions. GODS and GOSE scores were dichotomized for statistical analysis of functional capacity into Favorable Outcome (Moderate Disability, Severe Moderate Disability, Good Recovery, and Complete Recovery) and Unfavorable Outcome (Persistent Vegetative State, Severe Disability, and Severe Severe Disability). Treatment and Data Analysis The collected data were stored in a computerized database restricted to the research team, password protected. Descriptive statistics were performed for the sample characterization variables and for the description of S100B values detected in plasma and saliva. The Mann–Whitney test was used to verify differences in S100B concentrations between deceased and surviving patients, and between patients with unfavorable and favorable outcomes after TBI, since normal distribution was not observed when applying the Shapiro–Wilk test. A Receiver Operating Characteristic (ROC) curve was constructed to evaluate the discriminative ability of salivary and plasma S100B for predicting vital status and functional capacity at hospital discharge and three months post-trauma. Functional capacity analyses were dichotomized into Favorable and Unfavorable Outcomes and included only survivors of TBI. From these curves, the areas under the curve (AUC) with their 95% confidence intervals (CI) were determined. Test accuracy was classified as poor (AUC = 0.5–0.6), fair (AUC = 0.6–0.7), low (AUC = 0.7–0.8), good (AUC = 0.8–0.9), or excellent (AUC > 0.9) 30 . Additionally, the S100B concentration cutoff point was defined using the Youden index, from which accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were calculated for both saliva and plasma. Statistical analyses were conducted using R® software, with a significance level of 5%. Ethical Procedures This research was part of a thematic project that was approved by the Research Ethics Committee of the four study sites, with approvals registered on the Plataforma Brasil under numbers 31875020.9.0000.0105 (University Hospital of the State University of Ponta Grossa) and 46035921.2.3001.0068 (Hospital das Clínicas of the Faculty of Medicine, University of São Paulo, and Hospital Nove de Julho), and by the Ethics Committee of Santa Casa de Ponta Grossa, document n° 481. The Informed Consent Form (ICF) was presented to the patient or responsible family member after the participant’s hospital admission, at an appropriate time, in a quiet location, and with respect for privacy. Two copies of the ICF were signed by both the researcher and the patient or family member, with one copy retained by each party. Recruitment, Inclusion, and Follow-up of Participants Seventy-three patients with blunt TBI were recruited at the study sites, of whom 57 were included. Among the participants, 32 had mild TBI (56.14%), 10 had moderate TBI (17.54%), and 15 had severe TBI (26.32%). The main cause of exclusion was severe extracranial injury (AIS ≥ 3), which accounted for 62.50% of excluded cases, followed by neurological disorders (25.00%). Other reasons for exclusion included psychiatric disorders with impaired functional capacity and insufficient salivary volume for protein quantification; (Figure 1). All patients were followed until hospital discharge and assessed using the GODS. During the three-month follow-up, when the GOSE was applied, one patient with a history of social vulnerability was lost to follow-up, as they did not return to the outpatient clinic and could not be contacted by phone. Participant Characteristics The participants in this study were predominantly male (70.17%), white (70.17%), living with a partner (64.91%), and employed in the labor market (78.95%). The median age was 39 years (range: 19–59 years). The main external causes of TBI were falls (42.11%) and land transport accidents (36.84%). Comorbidities were present in 31.58% of cases, all requiring continuous medication use. At hospital admission, the median GCS score was 14.00 (Q1: 7.50 – Q3: 15.00), and the median hospital length of stay was 2 days (Q1: 1.00 – Q3: 9.00). Approximately 16% of the patients underwent neurosurgical interventions, and the primary disposition following the initial evaluation was observation in the emergency department (75%), while two patients were admitted directly to the intensive care unit. Mortality was 8.77% by hospital discharge and 12.50% at three months post-discharge. Among survivors, 9 (17.30%) presented an unfavorable outcome and 43 (87.76%) a favorable outcome at hospital discharge. At three months post-trauma, 6 patients had an unfavorable outcome, and 43 had a favorable outcome. Median concentrations of S100B protein were 17.50 pg/mL (Q1: 0.00 – Q3: 44.00) in plasma and 5.73 pg/mL (Q1: 0.00 – 26.00) in saliva. At both hospital discharge and three months post-trauma, patients who died exhibited higher plasma (p=0.0021 and 0.0025, respectively) and salivary (p=0.0086 and 0,0002, respectively) S100B concentrations compared to survivors (Figure 2a–d). Similarly, higher protein levels were observed in patients with unfavorable outcomes compared to those with favorable outcomes (p=0.0002 and 0.0005, plasma, hospital discharge and after three months, respectively; p<0.0001 and p=0.0055, saliva, hospital discharge and after three months, respectively) (Figure 3a–d). Performance of S100B Protein in Plasma and Saliva for Predicting Death The area under the ROC curve (AUC) for salivary S100B (0.84) was higher than for plasma S100B (0.77) in predicting death during hospital admission. However, sensitivity and negative predictive value were 100.00% for both biofluids, while accuracy and specificity were higher in plasma at the established cutoff point. Among the AUC-derived metrics, the low positive predictive value is noteworthy, at 26.30% for plasma and 19.20% for saliva (Figure 4). S100B demonstrated good predictive ability for death up to three months after TBI, with an AUC of 0.83 (95% CI 0.73–0.94) in plasma and 0.88 (95% CI 0.77–0.99) in saliva. Accuracies were 80.40% (95% CI 68.00–88.80) for plasma and 82.10% (95% CI 70.00–90.20) for saliva, based on the defined cutoff values. In plasma, sensitivity and negative predictive value again reached 100%, whereas saliva showed higher specificity. For both biofluids, positive predictive values remained low: 38.90% for plasma and 40.00% for saliva (Figure 5). Performance of S100B Protein in Plasma and Saliva for Predicting Unfavorable Outcomes S100B protein showed good predictive ability for unfavorable outcomes at hospital discharge, both in plasma (AUC 0.86; 95% CI 0.72–0.99) and saliva (AUC 0.90; 95% CI 0.81–0.99). All nine TBI patients with unfavorable outcomes at discharge had salivary S100B concentrations above the cutoff value, achieving 100% sensitivity and negative predictive value. In plasma, sensitivity was 77.80%, as two patients with S100B concentrations below the cutoff still presented unfavorable outcomes at discharge. Specificity was higher in plasma (88.40%) compared to saliva (76.70%), whereas positive predictive values remained low for both saliva (47.40%) and plasma (58.30%) (Figure 6). At three months post-TBI, the discriminative capacity of plasma S100B for functional outcomes was slightly higher than that of saliva; however, both biofluids demonstrated good performance (AUC = 0.89; 95% CI 0.75–1.00 for plasma and AUC = 0.84; 95% CI 0.72–0.96 for saliva). All six patients with unfavorable outcomes at three months had salivary S100B values above the cutoff, again achieving 100% sensitivity and negative predictive value. In plasma, sensitivity and negative predictive value were lower (83.30% and 97.50%, respectively). Positive predictive values remained low in these analyses due to independent patients at three months with plasma levels above the cutoff point (Figure 7). Discussion The results of this study demonstrated higher plasma and salivary S100B concentrations in patients who died or had unfavorable outcomes compared to those with better prognosis (survivors and patients with favorable outcomes). Similar findings have been reported in other investigations, with higher serum S100B concentrations in the acute phase of TBI among patients who died or presented impaired functional capacity up to hospital discharge 26,31 or within three months post-trauma 32-35 . A systematic review of studies measuring S100B in blood samples from patients with moderate and severe TBI indicated that, regardless of the time elapsed after trauma, protein levels were significantly higher in patients who became dependent or died 36 . In the present study, serum S100B demonstrated good predictive ability for in-hospital mortality and for mortality up to three months post-trauma, with AUC values of 0.77 and 0.83, respectively. Previous studies involving patients with moderate and severe TBI 26,37-42 reported AUC values ranging from 0.67 to 0.96 for predicting in-hospital mortality, indicating, except for one study 40 , good or excellent discriminative capacity of this protein. For prediction of outcomes at three months, two studies of moderate and severe TBI 32,36 reported AUC values of 0.68 and 0.69, suggesting unsatisfactory predictive performance of S100B at this later timepoint. In this investigation, AUC values were higher at three months than at hospital discharge, which may be explained by the predominance of mild TBI in the sample and by the early timing of blood collection compared with other studies. A recent meta-analysis 36 reported that samples collected six hours or more after trauma had better predictive performance for vital status at hospital discharge (pooled AUC 0.842; 95% CI 0.770–0.914) than early samples (pooled AUC 0.778; 95% CI 0.703–0.854). S100B was highly sensitive for predicting death at hospital discharge in both plasma and saliva, with all individuals who died presenting levels above the cutoff point. Sensitivity was higher in plasma than in saliva for predicting death up to three months; however, in both periods and matrices, a high frequency of false positives was observed, with survivors showing levels above the cutoff. The protein identified a subgroup with greater probability of death by discharge, although positive predictive values were only 26.30% (plasma) and 19.20% (saliva). For deaths up to three months, a plasma cutoff value was also observed beyond which mortality occurred; however, the probability of death among those above this threshold was 38.40%. Salivary S100B demonstrated superior discriminative capacity for death compared with plasma, both at hospital discharge (AUC 0.84 vs. 0.77) and at three months (AUC 0.88 vs. 0.83). Nevertheless, no previous studies have been identified that evaluated the predictive ability of S100B for mortality using saliva as a matrix. Functional dependency is another clinically relevant outcome of TBI, with considerable personal and social impact, and is the leading cause of disability in young adults 43 . Elevated S100B concentrations have been associated with dependency in several studies 32,36,44-49 as increased levels of this protein in blood and other biofluids are linked to both primary and secondary brain injury. Moreover, high S100B concentrations impair neurogenesis, reinforcing the negative correlation between serum S100B levels and dependency scores on the Glasgow Outcome Scale and its variants, with patients showing higher protein levels presenting more severe disability after TBI. Functional capacity at hospital discharge remains underexplored in research on post-traumatic recovery. Although no studies have reported the AUC of S100B for this outcome, one study 49 found higher protein levels among individuals with functional impairment at discharge. In the present study, both salivary and plasma S100B showed good predictive performance for dependency at discharge (AUC 0.90 and 0.86, respectively) and at three months (AUC 0.84 and 0.89, respectively). Sensitivity was higher in saliva at both timepoints, although positive predictive values remained low in both matrices. The literature reveals wide variability in the predictive capacity of serum S100B for dependency at three months post-trauma, with AUC values ranging from 0.58 to 0.94 46,48,50 . In this study, AUC values were 0.89 for plasma and 0.84 for saliva. For saliva, S100B achieved 100% sensitivity and positive predictive value at the cutoff of 13.75 pg/mL for predicting dependency at both discharge and three months. In plasma, sensitivity was lower, but specificity was close to 90% and negative predictive value was ≥ 95%, indicating a high likelihood of independence in individuals with values below the cutoff. Overall, saliva proved to be a promising matrix for predicting death and functional dependency in TBI patients via S100B, with AUC values superior to plasma in the prediction of in-hospital mortality, three-month mortality, and dependency at discharge. For other ROC-based metrics, saliva performed equally well or better than plasma, underscoring its prognostic potential despite the absence of previous validation studies in this matrix. According to the findings of this research, S100B concentrations may provide important support for clinical decision-making, not only for predicting mortality but also for early identification of functional deficits. Nevertheless, further studies are required to validate these results, clarify the mechanisms of protein transfer between biofluids, establish temporal variations of the biomarker after trauma, define clinical cutoff points, and better understand the relationship between S100B and secondary events of TBI . Among the limitations of this study, the sample size was constrained by the financial resources available for the acquisition of materials for sample collection and analysis, considering that the evaluation of saliva samples was a choice made to maintain the methodological rigor of the study. A notable strength of this research was the multicenter data collection, conducted in public and private hospitals across different states, which enhances the representativeness of the population; however, further studies in diverse clinical and geographic settings are still needed. Conclusions The analysis of the capacity of plasma and salivary S100B to predict death and unfavorable outcomes in survivors at hospital discharge and three months after blunt TBI allowed the conclusion that the protein’s predictive ability was significant at both time points post-trauma, although false-positive cases were frequently observed for the prognosis of these outcomes. In the analyses performed, saliva showed performance comparable to or better than plasma, a biofluid widely used in studies on S100B, suggesting that saliva may be a promising matrix for this TBI biomarker, allowing less invasive collection with lower risks and costs. CRediT authorship contribution statement Thamires de Oliveira Rocha : Writing – review & editing, Writing – original draft, Visualization, Resources, Methodology, Investigation, Formal analysis, Conceptualization. Lillian Caroline Fernandes : Writing – review & editing, Writing – original draft, Visualization, Supervision, Resources, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Dyenily Alessi Sloboda : Writing – review & editing, Writing – original draft, Resources, Methodology, Investigation, Funding acquisition, Data curation, Conceptualization. Leda Leme Talib : Writing – review & editing, Writing – original draft, Visualization, Supervision, Resources, Project administration, Methodology, Conceptualization. Wellingson Silva Paiva : Writing – review & editing, Writing – original draft, Resources, Project administration, Methodology, Conceptualization. Lilia de Souza Nogueira : Writing – review & editing, Writing – original draft, Supervision, Resources, Project administration, Methodology, Funding acquisition, Conceptualization. Regina Marcia Cardoso de Sousa : Writing – review & editing, Writing – original draft, Visualization, Supervision, Resources, Project administration, Methodology, Conceptualization. Potential Conflicts of Interest Nothing to report. Data Availability Research data are not shared. Funding This study was financed in part by the Coordenação de Aperfeiçoamento de Ensino do Nível Superior (CAPES), Brazil – Finance Code 001 (LSN). The materials used for the collection and analysis of biological samples were provided through the academic excellence program of the Postgraduate Program in Adult Health Nursing (PROESA), School of Nursing, University of São Paulo, as part of a proposal submitted by Fernandes LC and Sloboda DA in March 2020. Graphical Abstract • Plasma and salivary S100B levels were measured in patients with moderate and severe blunt TBI. • Protein levels were higher in patients who died or had adverse outcomes at hospital discharge and three months after injury. • Plasma and salivary S100B demonstrated good discriminative ability regarding vital status and functional dependence in patients with TBI. References 1 Dewan, MC, Rattani, A, Gupta, S, et al. Estimating the global incidence of traumatic brain injury. Journal of Neurosurgery. 2019;130(4):1080-1097. https://doi.org/10.3171/2017.10.JNS17352 2 Rajiv S, Kishor C, Saurabh S, et al. 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BioMed Res Int. 2021;2021:2398488. DOI: 10.1155/2021/2398488 50 Yu S, Choi HJ, Kim BC, et al. Prognosis Prediction in Severe Traumatic Brain Injury According to Initial Time of Brain Computed Tomography Scan Using the Rotterdam Scoring System. Korean Journal of Neurotrauma. 2022;18(2):161-168. DOI: 10.13004/kjnt.2022.18.e53 Figure 1. Flowchart of inclusion and follow-up of patients with blunt TBI in the study. Figure 2. Comparison of plasma and salivary S100B concentrations in patients alive and deceased at hospital discharge and three months after trauma. Figure 3. Comparison of plasma and salivary S100B concentrations in patients with favorable and unfavorable outcomes at hospital discharge and three months after trauma. Figure 4. Performance of plasma and salivary S100B in predicting patient mortality up to hospital discharge. Figure 5. Performance of plasma and salivary S100B in predicting mortality up to 3 months after blunt traumatic brain injury. Figure 6. Performance of plasma and salivary S100B in predicting unfavorable outcomes at hospital discharge. Figure 7. Performance of plasma and salivary S100B in predicting unfavorable outcomes at 3 months after blunt traumatic brain injury. Supplementary Material File (figures_rochato.docx) Download 1.90 MB Information & Authors Information Version history V1 Version 1 20 October 2025 DOI 10.22541/au.176100328.81668140/v1 Copyright This work is licensed under a Non Exclusive No Reuse License. Authors Affiliations Thamires de Oliveira Rocha 0009-0009-9618-3836 [email protected] USP View all articles by this author Lillian Caroline Fernandes Universidade de São Paulo View all articles by this author Dyenilly Alessi Sloboda Universidade Estadual de Ponta Grossa View all articles by this author Leda Talib 0000-0001-5866-1993 Laboratory of Neuroscience (LIM-27), Department and Institute of Psychiatry, University of Sao Paulo, Brazil. View all articles by this author Wellingson Silva Paiva Universidade de São Paulo View all articles by this author Lilia de Souza Nogueira Universidade de São Paulo View all articles by this author Regina Márcia Cardoso de Sousa Universidade de São Paulo View all articles by this author Metrics & Citations Metrics Article Usage 161 views 91 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Thamires de Oliveira Rocha, Lillian Caroline Fernandes, Dyenilly Alessi Sloboda, et al. Plasma and Salivary S100B in the Prognosis of Vital Status and Functional Dependence in Patients with Blunt Traumatic Brain Injury. Authorea . 20 October 2025. DOI: https://doi.org/10.22541/au.176100328.81668140/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. 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