Rapid measurement of S-100B serum protein levels by Elecsys S100 immunoassay in patients undergoing carotid artery stenting or endarterectomy

A simple electrochemical immunosensor based on a chitosan/reduced graphene oxide nanocomposite for sensitive detection of biomarkers of malignant melanoma

The sensitive and specific detection of tumor biomarkers is crucial for early diagnosis and treatment of malignant melanoma. Immunoassay with a simple sensing interface and high sensitivity is highly desirable. In this work, a simple electrochemical immunosensor based on a chitosan/reduced graphene oxide (CS–rGO) nanocomposite was developed for sensitive determination of an S-100B protein, a tumor marker of malignant melanoma. CS–rGO nanocomposite were prepared by chemical reduction of graphene oxide in the presence of chitosan and modified on glassy carbon electrode (GCE) to provide a biofriendly, conductive, and easily chemically modified matrix for further immobilization of antibodies. Anti-S-100B antibodies were grafted onto the chitosan molecules to fabricate the immunorecognition interface by a simple glutaraldehyde cross-linking method. Electrochemical determination of S-100B was achieved by measuring the decreased current signal of solution phase electrochemical probes, which originated from the increased steric hindrance and insulation caused by the formation of antigen–antibody complexes at the electrode interface. Due to the good conductivity, high surface area, excellent biocompatibility, and good film-forming ability of CS–rGO, the constructed immunosensor exhibited good stability, high selectivity and sensitivity, a wide dynamic range from 10 fg mL⁻¹ to 1 ng mL⁻¹ and a low limit of detection of 1.9 pg mL⁻¹ (S/N = 3). Moreover, the sensor was also applicable for the sensitive detection of S-100B protein in real human serum samples.

Simple electrochemical immunosensor is easily fabricated based on chitosan/reduce graphene oxide nanocomposite for sensitive determination of a tumor marker of malignant melanoma.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

Background

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein “biomarker” of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

Results

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

Conclusion

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

A review of the clinical utility of serum S100B protein levels in the assessment of traumatic brain injury

BACKGROUND

In order to improve injury assessment of brain injuries, protein markers of pathophysiological processes and tissue fate have been introduced in the clinic. The most studied protein "biomarker" of cerebral damage in traumatic brain injury (TBI) is the protein S100B. The aim of this narrative review is to thoroughly analyze the properties and capabilities of this biomarker with focus on clinical utility in the assessment of patients suffering from TBI.

RESULTS

S100B has successfully been implemented in the clinic regionally (1) to screen mild TBI patients evaluating the need to perform a head computerized tomography, (2) to predict outcome in moderate-to-severe TBI patients, (3) to detect secondary injury development in brain-injured patients and (4) to evaluate treatment efficacy. The potential opportunities and pitfalls of S100B in the different areas usually refer to its specificity and sensitivity to detect and assess intracranial injury.

CONCLUSION

Given some shortcomings that should be realized, S100B can be used as a versatile screening, monitoring and prediction tool in the management of TBI patients.

Utility of neuron-specific enolase in traumatic brain injury; relations to S100B levels, outcome, and extracranial injury severity

BACKGROUND

In order to improve assessment and outcome prediction in patients suffering from traumatic brain injury (TBI), cerebral protein levels in serum have been suggested as biomarkers of injury. However, despite much investigation, biomarkers have yet to reach broad clinical utility in TBI. This study is a 9-year follow-up and clinical experience of the two most studied proteins, neuron-specific enolase (NSE) and S100B, in a neuro-intensive care TBI population. Our aims were to investigate to what extent NSE and S100B, independently and in combination, could predict outcome, assess injury severity, and to investigate if the biomarker levels were influenced by extracranial factors.

METHODS

All patients treated at the neuro-intensive care unit at Karolinska University Hospital, Stockholm, Sweden between 2005 and 2013 with at least three measurements of serum S100B and NSE (sampled twice daily) were retrospectively included. In total, 417 patients fulfilled the criteria. Parameters were extracted from the computerized hospital charts. Glasgow Outcome Score (GOS) was used to assess long-term functional outcome. Univariate, and multivariate, regression models toward outcome and what explained the high levels of the biomarkers were performed. Nagelkerke's pseudo-R(2) was used to illustrate the explained variance of the different models. A sliding window assessed biomarker correlation to outcome and multitrauma over time.

RESULTS

S100B was found a better predictor of outcome as compared to NSE (area under the curve (AUC) samples, the first 48 hours had Nagelkerke's pseudo-R(2) values of 0.132 and 0.038, respectively), where the information content of S100B peaks at approximately 1 day after trauma. In contrast, although both biomarkers were independently correlated to outcome, NSE had limited additional predictive capabilities in the presence of S100B in multivariate models, due to covariance between the two biomarkers (correlation coefficient 0.673 for AUC 48 hours). Moreover, NSE was to a greater extent correlated to multitrauma the first 48 hours following injury, whereas the effect of extracerebral trauma on S100B levels appears limited to the first 12 hours.

CONCLUSIONS

While both biomarkers are independently correlated to long-term functional outcome, S100B is found a more accurate outcome predictor and possibly a more clinically useful biomarker than NSE for TBI patients.

Kinetic modelling of serum S100b after traumatic brain injury

Background

An understanding of the kinetics of a biomarker is essential to its interpretation. Despite this, little kinetic modelling of blood biomarkers can be found in the literature. S100b is an astrocyte related marker of brain injury used primarily in traumatic brain injury (TBI). Serum levels are expected to be the net result of a multi-compartmental process. The optimal sample times for TBI prognostication, and to follow injury development, are unclear. The purpose of this study was to develop a kinetic model to characterise the temporal course of serum S100b concentration after primary traumatic brain injury.

Methods

Data of serial serum S100b samples from 154 traumatic brain injury patients in a neurointensive care unit were retrospectively analysed, including only patients without secondary peaks of this biomarker. Additionally, extra-cranial S100b can confound samples earlier than 12 h after trauma and were therefore excluded. A hierarchical, Bayesian gamma variate kinetic model was constructed and the parameters estimated by Markov chain Monte Carlo sampling.

Results

We demonstrated that S100b concentration changes dramatically over timescales that are clinically important for early prognostication with a peak at 27.2 h (95 % credible interval [25.6, 28.8]). Baseline S100b levels was found to be 0.11 μg/L (95 % credible interval [0.10, 0.12]).

Conclusions

Even small differences in injury to sample time may lead to marked changes in S100b during the first days after injury. This must be taken into account in interpretation. The model offers a way to predict the peak and trajectory of S100b from 12 h post trauma in TBI patients, and to identify deviations from this, possibly indicating a secondary event. Kinetic modelling, providing an equation for the peak and projection, may offer a way to reduce the ambiguity in interpretation of, in time, randomly sampled acute biomarkers and may be generally applicable to biomarkers with, in time, well defined hits.

Secondary peaks of S100B in serum relate to subsequent radiological pathology in traumatic brain injury

INTRODUCTION

Patients suffering from severe traumatic brain injury (TBI) often develop secondary brain lesions that may worsen outcome. S100B, a biomarker of brain damage, has been shown to increase in response to secondary cerebral deterioration. The aim of this study was to analyze the occurrence of secondary increases in serum levels of S100B and their relation to potential subsequent radiological pathology present on CT/MRI-scans.

METHODS

Retrospective study from a trauma level 1 hospital, neuro-intensive care unit. 250 patients suffering from TBI were included. Inclusion required a minimum of two radiological examinations and at least three serum samples of S100B, with at least one >48 h after trauma.

RESULTS

Secondary pathological findings on CT/MRI, present in 39 % (n = 98) of the patients, were highly correlated to secondary increases of ≥0.05 μg/L S100B (P < 0.0001, pseudo-R (2) 0.532). Significance remained also after adjusting for known important TBI predictors. In addition, secondary radiological findings were significantly correlated to outcome (Glasgow Outcome Score, GOS) in uni-(P < 0.0001, pseudo-R (2) 0.111) and multivariate analysis. The sensitivity and specificity of detecting later secondary radiological findings was investigated at three S100B cut-off levels: 0.05, 0.1, and 0.5 μg/L. A secondary increase of ≥0.05 μg/L had higher sensitivity (80 %) but lower specificity (89 %), compared with a secondary increase of ≥0.5 μg/L (16 % sensitivity, 98 % specificity), to detect secondary radiological findings.

CONCLUSIONS

Secondary increases in serum levels of S100B, even as low as ≥0.05 μg/L, beyond 48 h after TBI are strongly correlated to the development of clinically significant secondary radiological findings.

Comparisons of cognitive function and serum S-100B level between diabetic and non-diabetic patients after the implantation of carotid artery stent (CAS)

To investigate cognitive function improvement in diabetic and non-diabetic patients after the implantation of Carotid Artery Stent (CAS), 128 patients suffering severe carotid stenosis were successfully enrolled in this study. Tests including, the Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), Clock Drawing Test (CDT), Hasegawa's Dementia Scale-Revised (HDS-R) and the serum levels of S-100B, were all measured at baseline for 3 months after the implantation of CAS. The baseline characteristics were similar between the patients with and without diabetes. 3 months after the implantation, significant improvements in MMSE (24.8 ± 2.2 vs. 25.2 ± 2.1, p=0.003), MoCA (25.6 ± 2.0 vs. 26.1 ± 1.9, p=0.000), ADAS-Cog (6.5 ± 1.3 vs. 6.1 ± 1.3, p=0.000), and CDT (3.3 ± 0.7 vs. 3.5 ± 0.7, p=0.034) were observed in the non-diabetic group. In contrast, there was no significant improvement in any of the cognitive test for the diabetic group. Another interesting discovery was the CAS procedure significantly decreased the S-100B level in the non-diabetic group (0.11 ± 0.04 ng/mL vs. 0.10 ± 0.04 ng/mL, p=0.000), but similar phenomena were not discovered in the diabetic group. In this light, the change of the S-100B level was negatively correlated with the results in the MMSE (p<0.01) and the MoCA (p<0.01) tests, and positively correlated with the result in ADAS-Cog (p<0.05) test. Our findings suggest that the CAS-induced beneficial effects on cognitive function might have a correlation relationship with the serum level of S-100B.

S100B is an important outcome predictor in traumatic brain injury

The objective of the study was to examine how S100B, a biomarker of traumatic brain injury (TBI), contributes to outcome prediction after adjusting for known parameters, including age, Glasgow Coma Scale (GCS), pupil reaction, and computed tomography (CT) variables; to examine which parameters have the best correlation to elevated serum levels of S100B; and to investigate when to sample S100B to achieve the strongest association to outcome. This retrospective study included 265 patients with TBI admitted to the neurointensive care unit, Karolinska University Hospital Solna, Stockholm, Sweden. Univariate and multivariate proportional odds regressions were performed to determine parameters most closely related to outcome, and how S100B adds to prediction accuracy. Age (p<0.0001), pupil reaction (p<0.0001), and levels of S100B (p<0.0001) had the strongest statistical correlation to outcome. The area under curve of S100B, the first 48 h after trauma, yielded an additional explained variance of 6.6% in excess of known outcome parameters, including age, GCS, pupil reaction, and CT variables, themselves exhibiting an explained variance of 29.3%. S100B adds substantial information regarding patient outcome, in excess of that provided by known parameters. Only CT variables were found to be significant predictors of increased levels of S100B in uni- and multivariate analysis. Early samples of S100B, within 12 h after trauma, appear to have little prognostic value, and S100B should likely be sampled 12-36 h following trauma to best enhance TBI outcome prediction.

Homogeneous immunosubtraction integrated with sample preparation enabled by a microfluidic format

Immunosubtraction is a powerful and resource-intensive laboratory medicine assay that reports both protein mobility and binding specificity. To expedite and automate this electrophoretic assay, we report on advances to the electrophoretic immunosubtraction assay by introducing a homogeneous, not heterogeneous, format with integrated sample preparation. To accomplish homogeneous immunosubtraction, a step-decrease in separation matrix pore-size at the head of a polyacrylamide gel electrophoresis (PAGE) separation channel enables "subtraction" of target analyte when capture antibody is present (as the large immune-complex is excluded from PAGE), but no subtraction when capture antibody is absent. Inclusion of sample preparation functionality via small pore size polyacrylamide membranes is also key to automated operation (i.e., sample enrichment, fluorescence sample labeling, and mixing of sample with free capture antibody). Homogeneous sample preparation and assay operation allows on-the-fly, integrated subtraction of one to multiple protein targets and reuse of each device. Optimization of the assay is detailed which allowed for ~95% subtraction of target with 20% non-specific extraction of large species at the optimal antibody-antigen ratio, providing conditions needed for selective target identification. We demonstrate the assay on putative markers of injury and inflammation in cerebrospinal fluid (CSF), an emerging area of diagnostics research, by rapidly reporting protein mobility and binding specificity within the sample matrix. We simultaneously detect S100B and C-reactive protein, suspected biomarkers for traumatic brain injury (TBI), in ~2 min. Lastly, we demonstrate S100B detection (65 nM) in raw human CSF with an estimated lower limit of detection of 3.25 nM, within the clinically relevant concentration range for detecting TBI in CSF. Beyond the novel CSF assay introduced here, a fully automated immunosubtraction assay would impact a spectrum of routine but labor and time-intensive laboratory medicine assays.

Can early serum levels of S100B protein predict the prognosis of patients with out-of-hospital cardiac arrest?

OBJECTIVE

This study aims to know if the level of S100B protein at the initiation of cardiopulmonary resuscitation (CPR) and immediately after return of spontaneous circulation (ROSC) can predict clinical outcome.

MATERIALS AND METHODS

A prospective observational study from December 2004 to October 2006 was conducted in an urban tertiary hospital emergency department. Clinical demographics for out-of-hospital cardiac arrest patients were collected based on the Utstein style. Outcomes collected included ROSC for 20min, survival to admission, survival and Glasgow Outcome Scale (GOS) at 1 month. S100B protein was measured twice before starting CPR (first S100B) and immediately after ROSC (second S100B). We investigated the association between S100B protein levels and clinical outcomes using a multivariate logistic regression model.

RESULTS

A total of 151 patients were included (age: 60.2+/-16.8 years, male: 64.2%). Of these, 60 (39.7%) had ROSC and 46 (30.5%) survived to admission. After 1 month, 12 (8.0%) survived and only three patients showed good GOS (>/=4 points). The S100B levels were not different for ROSC, survival to admission and 1-month survival between survivors and non-survivors (p>0.05, first and second S100 B level). For the witnessed out-of-hospital cardiac arrest (OHCA) group (N=87), only the first S100B (1.22+/-0.85mugl(-1) vs. 3.91+/-4.25mugl(-1), p<0.001) showed significant difference for 1-month survival between survivors and non-survivors. The first S100B showed significant association with survival to emergency department (ED) but not 1-month survival (adjusted odds ratio (OR)=0.905, 95% confidence interval=0.821-0.998).

CONCLUSION

Higher levels of S100B at start of CPR were significantly associated with lower survival to admission, and not for 1-month survival.

Effects of mode of delivery on maternal–neonatal plasma antioxidant status and on protein S100B serum concentrations

OBJECTIVE

To investigate the effect of the mode of labour and delivery on total antioxidant status (TAS) and on the protein S100B serum concentrations in mothers and their newborns.

MATERIAL AND METHODS

Sixty women with normal pregnancies were divided into three groups: Group A (n = 20) with normal labour and vaginal delivery (VG), group B (n = 18) with prolonged labour+VG and group C (n = 22) with scheduled caesarean section (CS). Blood was obtained at the beginning of the labour process and immediately after delivery (pre- and post-delivery) as well as from the umbilical cord (CB). TAS and creatine kinase (CK) were measured using commercial kits. Serum S100B levels were evaluated with the electrochemiluminescence immunoassay "ECLIA" on the ROCHE ELECSYS 2010 immunoassay analyser.

RESULTS

Post-delivery, TAS levels were significantly decreased in group A and especially in group B. S100B levels were increased in group B (0.0712+/-0.02 microg/L) as compared with those of group A (0.0567+/-0.03 microg/L, p<0.01) and group C (0.038+/-0.03 microg/L, p<0.01), the levels in group C remaining practically unaltered (pre- versus post-delivery). In the newborns, S100B levels were almost 2-fold higher in group B (0.67+/-0.18 microg/L) than those in group A (0.40+/-0.05 microg/L p<0.001) and group C (0.31+/-0.04 microg/L p<0.001). A negative correlation was found between TAS and S100B protein (r = -0.61, p<0.001), the latter positively correlated to CK (r = 0.48, p<0.01).

CONCLUSIONS

The increased S100B serum levels in the mothers of group B, post-delivery, may have been due to the long-lasting, oxidative and/or psychogenic stress. The observed remarkably high levels of S100B in the group B newborns may have been due to compressive conditions on the foetus brain during this mode of delivery.

Use of wireless telephones and serum S100B levels: a descriptive cross-sectional study among healthy Swedish adults aged 18-65 years

BACKGROUND

Since the late 1970s, experimental animal studies have been carried out on the possible effects of low-intensive radiofrequency fields on the blood-brain barrier (BBB), but no epidemiological study has been published to date.

OBJECTIVE

Using serum S100B as a putative marker of BBB dysfunction we performed a descriptive cross-sectional study to investigate whether protein levels were higher among frequent than non-frequent users of mobile and cordless desktop phones.

METHOD

One thousand subjects, 500 of each sex aged 18-65 years, were randomly recruited using the population registry. Data on wireless phone use were assessed by a postal questionnaire and blood samples were analyzed for S100B.

RESULTS

The response rate was 31.4%. The results from logistic and linear regression analyses were statistically insignificant, with one exception: the linear regression analysis of latency for UMTS use, which after stratifying on gender remained significant only for men (p = 0.01; n = 31). A low p-value (0.052) was obtained for use of cordless phone (n = 98) prior to giving the blood samples indicating a weak negative association. Total use of mobile and cordless phones over time yielded odds ratio (OR) 0.8 and 95% confidence interval (CI) 0.3-2.0 and use on the same day as giving blood yielded OR=1.1, CI=0.4-2.8.

CONCLUSIONS

This study failed to show that long- or short-term use of wireless telephones was associated with elevated levels of serum S100B as a marker of BBB integrity. The finding regarding latency of UMTS use may be interesting but it is based on small numbers. Generally, S100B levels were low and to determine whether this association - if causal - is clinically relevant, larger studies with sufficient follow-up are needed.

Serum S100B levels after meningioma surgery: A comparison of two laboratory assays

Background

S100B protein is a potential biomarker of central nervous system insult. This study quantitatively compared two methods for assessing serum concentration of S100B.

Methods

A prospective, observational study performed in a single tertiary medical center. Included were fifty two consecutive adult patients undergoing surgery for meningioma that provided blood samples for determination of S100B concentrations. Eighty samples (40 pre-operative and 40 postoperative) were randomly selected for batch testing. Each sample was divided into two aliquots. These were analyzed by ELISA (Sangtec) and a commercial kit (Roche Elecsys^®) for S100B concentrations. Statistical analysis included regression modelling and Bland-Altman analysis.

Results

A parsimonious linear model best described the prediction of commercial kit values by those determined by ELISA (y = 0.045 + 0.277*x, x = ELISA value, R² = 0.732). ELISA measurements tended to be higher than commercial kit measurements. This discrepancy increased linearly with increasing S100B concentrations. At concentrations above 0.7 μg/L the paired measurements were consistently outside the limits of agreement in the Bland-Altman display. Similar to other studies that used alternative measurement methods, sex and age related differences in serum S100B levels were not detected using the Elecsys^® (p = 0.643 and 0.728 respectively).

Conclusion

Although a generally linear relationship exists between serum S100B concentrations measured by ELISA and a commercially available kit, ELISA values tended to be higher than commercial kit measurements particularly at concentrations over 0.7 μg/L, which are suggestive of brain injury. International standardization of commercial kits is required before the predictive validity of S100B for brain damage can be effectively assessed in clinical practice.

Biological and methodological features of the measurement of S100B, a putative marker of brain injury

The S100B astroglial protein is widely used as a parameter of glial activation and/or death in several conditions of brain injury. Cerebrospinal fluid and serum S100B variations have been proposed to evaluate clinical outcomes in these situations. Here, we briefly broach some aspects, commonly not sufficiently valorized, concerning the biology and measurements of this protein. S100B has molecular targets and activities in and outside of astrocytes, and variations of intra and extracellular content are not necessarily coupled. We discuss the extracellular origin of this protein in brain tissue, as well as extracerebral sources of this protein in serum, comparing it with other available protein markers of brain damage. The superestimation of the heterodimer S100A1-B in the current clinical literature is also analyzed. We affirm that poor dualistic views that consider S100B elevation as "bad" or "good" simplify clinical practice and delay our comprehension of the role of this protein, both in physiological conditions and in brain disorders.

Reliability of S100B in predicting severity of central nervous system injury

S100B is a protein biomarker that reflects CNS injury. It can be measured in the CSF or serum with readily available immunoassay kits. The excellent sensitivity of S100B has enabled it to confirm the existence of subtle brain injury in patients with mild head trauma, strokes, and after successful resuscitation from cardiopulmonary arrest. The extent of S100B elevation has been found to be useful in predicting clinical outcome after brain injury. Elevations of S100B above certain threshold levels might be able to reliably predict brain death or mortality. A normal S100B level reliably predicts the absence of significant CNS injury. The specificity of S100B levels as a reflection of CNS injury is compromised by the findings that extra-cranial injuries can lead to elevations in the absence of brain injury. This potential problem can most likely be avoided by measuring serial S100B levels along with other biomarkers and carefully noting peripheral injuries. Serum markers GFAP and NSE are both more specific for CNS injury and have little to no extra-cranial sources. Sustained elevations of S100B over 24 h along with elevations of GFAP and NSE can more reliably predict the extent of brain injury and clinical outcomes. In the future, S100B measurements might reliably predict secondary brain injury and enable physicians to initiate therapeutic interventions in a timelier manner. S100B levels have been shown to rise hours to days before changes in ICP, neurological examinations, and neuroimaging tests. S100B levels may also be used to monitor the efficacy of treatments.

Significance of Elecsys S100 immunoassay for real-time assessment of traumatic brain damage in multiple trauma patients

BACKGROUND

The neuroprotein S100 released into the circulation has been suggested as a reliable marker for primary brain damage. However, safe identification of relevant traumatic brain injury (TBI) may possibly be hampered by S100 release from peripheral tissue. The objective of this study was to measure early S100 levels using the Elecsys S100 immunoassay for real-time assessment of severe TBI in multiple trauma.

METHODS

Consecutively admitted multiple trauma patients (injury severity score >or=16 points) were stratified according to the results of the initial cerebral computed tomography (CCT) examination. S100 serum levels were determined at admission and at 6, 12, 24, 48 and 72 h after trauma. Data were correlated to creatine phosphokinase (CK) and lactate dehydrogenase (LDH) serum levels. Using receiver operating characteristic (ROC) analysis, the discriminating power of S100 measurement was calculated for the detection of CCT+ findings.

RESULTS

Median S100 levels of CCT+ patients (n=9; 37 years) decreased from 3.30 microg/L at admission to 0.41 microg/L 72 h after trauma. They revealed no significant differences to CCT- patients (n=18; 44 years), but remained elevated compared to controls. Median CK and LDH levels correlated with the corresponding S100 levels during the first 24 h after trauma. ROC analysis displayed a maximum area under the curve of only 0.653 at 12 h after trauma. No significant difference was calculated for the differentiation between CCT+ and CCT- patients.

CONCLUSIONS

Measurements of S100 serum levels using the Elecsys S100 immunoassay are not reliable for the real-time detection of severe TBI in multiple trauma patients. Due to soft tissue trauma or bone fractures, S100 is mainly released from peripheral sources such as adipocytes or skeletal muscle cells.