Plasma Glial Fibrillary Acidic Protein Levels Research Articles

Controlled Decompression Alleviates Brain Injury via Attenuating Oxidative Damage and Neuroinflammation in Acute Intracranial Hypertension.

Background The benefits of controlled decompression (CDC) for patients with acute intracranial hypertension especially in terms of alleviating the complications caused by rapid decompression (RDC) have been confirmed by clinical studies. This study is aimed at evaluating the therapeutic potency of CDC with ubiquitin C-terminal hydrolase-L1 (UCH-L1) and glial fibrillary acidic protein (GFAP) by investigating the potential molecular mechanism in the acute intracranial hypertension (AICH) rabbit model. Methods Male New Zealand white rabbits were randomly subdivided into the sham-operated (SH) group, CDC group, and RDC group. Blood plasma samples and brain tissue were collected 2 days before operation (baseline) and at 3, 6, 24, and 72 hours after operation to measure the levels of UCH-L1, GFAP, oxidative stress indicators, and inflammatory cytokines by performing ELISA or Western blot. The neurological score of the rabbits and brain water content was graded 24 h after surgery. qPCR, immunofluorescence, and FJ-C staining were conducted. Results CDC improved neurological function, lowered brain water content, ameliorated neuronal degeneration, attenuated oxidative damage, and inflammatory responses to a greater extent than RDC. Plasma UCH-L1 level was significantly lower in the CDC group at 3 h postoperatively than in the RDC group. CDC reduced plasma GFAP levels to various degrees at 3 h, 6 h, and 24 h postoperatively compared with RDC. Immunofluorescence confirmed that the expression of UCH-L1 and GFAP in the cortex of the CDC group was lower than that of the RDC group. Conclusions Our data collectively demonstrate that CDC could attenuate oxidative damage and inflammatory responses, downregulate UCH-L1 and GFAP levels, and contribute to an improved neuroprotective effect compared with RDC.

Differences Between Plasma and Cerebrospinal Fluid Glial Fibrillary Acidic Protein Levels Across the Alzheimer Disease Continuum

Glial fibrillary acidic protein (GFAP) is a marker of reactive astrogliosis that increases in the cerebrospinal fluid (CSF) and blood of individuals with Alzheimer disease (AD). However, it is not known whether there are differences in blood GFAP levels across the entire AD continuum and whether its performance is similar to that of CSF GFAP. To evaluate plasma GFAP levels throughout the entire AD continuum, from preclinical AD to AD dementia, compared with CSF GFAP. This observational, cross-sectional study collected data from July 29, 2014, to January 31, 2020, from 3 centers. The Translational Biomarkers in Aging and Dementia (TRIAD) cohort (Montreal, Canada) included individuals in the entire AD continuum. Results were confirmed in the Alzheimer's and Families (ALFA+) study (Barcelona, Spain), which included individuals with preclinical AD, and the BioCogBank Paris Lariboisière cohort (Paris, France), which included individuals with symptomatic AD. Plasma and CSF GFAP levels measured with a Simoa assay were the main outcome. Other measurements included levels of CSF amyloid-β 42/40 (Aβ42/40), phosphorylated tau181 (p-tau181), neurofilament light (NfL), Chitinase-3-like protein 1 (YKL40), and soluble triggering receptor expressed on myeloid cells 2 (sTREM2) and levels of plasma p-tau181 and NfL. Results of amyloid positron emission tomography (PET) were available in TRIAD and ALFA+, and results of tau PET were available in TRIAD. A total of 300 TRIAD participants (177 women [59.0%]; mean [SD] age, 64.6 [17.6] years), 384 ALFA+ participants (234 women [60.9%]; mean [SD] age, 61.1 [4.7] years), and 187 BioCogBank Paris Lariboisière participants (116 women [62.0%]; mean [SD] age, 69.9 [9.2] years) were included. Plasma GFAP levels were significantly higher in individuals with preclinical AD in comparison with cognitively unimpaired (CU) Aβ-negative individuals (TRIAD: Aβ-negative mean [SD], 185.1 [93.5] pg/mL, Aβ-positive mean [SD], 285.0 [142.6] pg/mL; ALFA+: Aβ-negative mean [SD], 121.9 [42.4] pg/mL, Aβ-positive mean [SD], 169.9 [78.5] pg/mL). Plasma GFAP levels were also higher among individuals in symptomatic stages of the AD continuum (TRIAD: CU Aβ-positive mean [SD], 285.0 [142.6] pg/mL, mild cognitive impairment [MCI] Aβ-positive mean [SD], 332.5 [153.6] pg/mL; AD mean [SD], 388.1 [152.8] pg/mL vs CU Aβ-negative mean [SD], 185.1 [93.5] pg/mL; Paris: MCI Aβ-positive, mean [SD], 368.6 [158.5] pg/mL; AD dementia, mean [SD], 376.4 [179.6] pg/mL vs CU Aβ-negative mean [SD], 161.2 [67.1] pg/mL). Plasma GFAP magnitude changes were consistently higher than those of CSF GFAP. Plasma GFAP more accurately discriminated Aβ-positive from Aβ-negative individuals than CSF GFAP (area under the curve for plasma GFAP, 0.69-0.86; area under the curve for CSF GFAP, 0.59-0.76). Moreover, plasma GFAP levels were positively associated with tau pathology only among individuals with concomitant Aβ pathology. This study suggests that plasma GFAP is a sensitive biomarker for detecting and tracking reactive astrogliosis and Aβ pathology even among individuals in the early stages of AD.

Development of a novel, sensitive translational immunoassay to detect plasma glial fibrillary acidic protein (GFAP) after murine traumatic brain injury

BackgroundGlial fibrillary acidic protein (GFAP) has emerged as a promising fluid biomarker for several neurological indications including traumatic brain injury (TBI), a leading cause of death and disability worldwide. In humans, serum or plasma GFAP levels can predict brain abnormalities including hemorrhage on computed tomography (CT) scans and magnetic resonance imaging (MRI). However, assays to quantify plasma or serum GFAP in preclinical models are not yet available.MethodsWe developed and validated a novel sensitive GFAP immunoassay assay for mouse plasma on the Meso Scale Discovery immunoassay platform and validated assay performance for robustness, precision, limits of quantification, dilutional linearity, parallelism, recovery, stability, selectivity, and pre-analytical factors. To provide proof-of-concept data for this assay as a translational research tool for TBI and Alzheimer’s disease (AD), plasma GFAP was measured in mice exposed to TBI using the Closed Head Impact Model of Engineered Rotational Acceleration (CHIMERA) model and in APP/PS1 mice with normal or reduced levels of plasma high-density lipoprotein (HDL).ResultsWe performed a partial validation of our novel assay and found its performance by the parameters studied was similar to assays used to quantify human GFAP in clinical neurotrauma blood specimens and to assays used to measure murine GFAP in tissues. Specifically, we demonstrated an intra-assay CV of 5.0%, an inter-assay CV of 7.2%, a lower limit of detection (LLOD) of 9.0 pg/mL, a lower limit of quantification (LLOQ) of 24.8 pg/mL, an upper limit of quantification (ULOQ) of at least 16,533.9 pg/mL, dilution linearity of calibrators from 20 to 200,000 pg/mL with 90–123% recovery, dilution linearity of plasma specimens up to 32-fold with 96–112% recovery, spike recovery of 67–100%, and excellent analyte stability in specimens exposed to up to 7 freeze-thaw cycles, 168 h at 4 °C, 24 h at room temperature (RT), or 30 days at − 20 °C. We also observed elevated plasma GFAP in mice 6 h after TBI and in aged APP/PS1 mice with plasma HDL deficiency. This assay also detects GFAP in serum.ConclusionsThis novel assay is a valuable translational tool that may help to provide insights into the mechanistic pathophysiology of TBI and AD.

Plasma glial fibrillary acidic protein is elevated in cognitively normal older adults at risk of Alzheimer\u2019s disease

Glial fibrillary acidic protein (GFAP), an astrocytic cytoskeletal protein, can be measured in blood samples, and has been associated with Alzheimer’s disease (AD). However, plasma GFAP has not been investigated in cognitively normal older adults at risk of AD, based on brain amyloid-β (Aβ) load. Cross-sectional analyses were carried out for plasma GFAP and plasma Aβ1–42/Aβ1–40 ratio, a blood-based marker associated with brain Aβ load, in participants (65–90 years) categorised into low (Aβ−, n = 63) and high (Aβ+, n = 33) brain Aβ load groups via Aβ positron emission tomography. Plasma GFAP, Aβ1–42, and Aβ1–40 were measured using the Single molecule array (Simoa) platform. Plasma GFAP levels were significantly higher (p < 0.00001), and plasma Aβ1–42/Aβ1–40 ratios were significantly lower (p < 0.005), in Aβ+ participants compared to Aβ− participants, adjusted for covariates age, sex, and apolipoprotein E-ε4 carriage. A receiver operating characteristic curve based on a logistic regression of the same covariates, the base model, distinguished Aβ+ from Aβ− (area under the curve, AUC = 0.78), but was outperformed when plasma GFAP was added to the base model (AUC = 0.91) and further improved with plasma Aβ1–42/Aβ1–40 ratio (AUC = 0.92). The current findings demonstrate that plasma GFAP levels are elevated in cognitively normal older adults at risk of AD. These observations suggest that astrocytic damage or activation begins from the pre-symptomatic stage of AD and is associated with brain Aβ load. Observations from the present study highlight the potential of plasma GFAP to contribute to a diagnostic blood biomarker panel (along with plasma Aβ1–42/Aβ1–40 ratios) for cognitively normal older adults at risk of AD.

Quantification of neurological blood‐based biomarkers in critically ill patients with COVID‐19

BackgroundMultiple neurological manifestations of COVID‐19 have been reported such as headache, anosmia, ischemic stroke, and cerebral hemorrhages. Objective characterization of the acute neurological damage in critically ill patients with COVID‐19 has not yet been reported.MethodWe performed a prospective observational study of plasma brain biomarkers in critically ill patients with respiratory failure that were diagnosed with (COVID‐19) or without (ICU control) COVID‐19. Demographics, co‐morbidities, daily clinical physiologic and laboratory data were collected. Plasma samples were drawn for measurement of neurofilament‐light chain (NF‐L), total tau (t‐tau), ubiquitin carboxy‐terminal hydrolase L1 (UCH‐L1), and glial fibrillary acidic protein (GFAP). The primary neurological outcome was delirium as defined by the intensive care delirium screening checklist (ICDSC, scale 1 ‐ 8). Associations between brain biomarkers and markers of respiratory failure of COVID‐19 were analyzed.Result27 patients with COVID‐19 and 19 ICU controls were enrolled. The concentration of plasma GFAP, UCH‐L1 and NF‐L levels was higher in both groups compared to healthy controls. Compared to ICU controls, patients with COVID‐19 had significantly higher GFAP (272 [150‐555] pg/ml vs 118 [78.5‐168] pg/ml, p=0.0009). In patients with COVID‐19, GFAP (rho=0.5115, p=0.0064), UCH‐L1 (rho=0.4056, p=0.0358) and NF‐L (rho=0.6223, p=0.0005) were positively correlated with the ICDSC score and were higher in patients diagnosed with delirium (ICDSC ≥4) in the COVID‐19 group but not ICU controls. There were no associations between PaO2/FiO2 or diagnosis of ARDS and plasma concentration of GFAP, t‐tau, UCH‐L1, or NF‐L in patients with COVID‐19.ConclusionPlasma GFAP is 2‐fold higher in critically ill patients with COVID‐19 compared to ICU controls, and higher concentrations of GFAP, UCH‐L1 and NF‐L are associated with delirium specifically in patients with COVID‐19.

ADHD May Associate With Reduced Tolerance to Acute Subconcussive Head Impacts: A Pilot Case-Control Intervention Study

Objective: To test our hypothesis that individuals with ADHD would exhibit reduced resiliency to subconcussive head impacts induced by ten soccer headings. Method: We conducted a case-control intervention study in 51 adults (20.6 ± 1.7 years old). Cognitive assessment, using ImPACT, and plasma levels of neurofilament-light (NF-L), Tau, glial-fibrillary-acidic protein (GFAP), and ubiquitin-C-terminal hydrolase-L1 (UCH-L1) were measured. Results: Ten controlled soccer headings demonstrated ADHD-specific transient declines in verbal memory function. Ten headings also blunted learning effects in visual memory function in the ADHD group while the non-ADHD counterparts improved both verbal and visual memory functions even after ten headings. Blood biomarker levels of the ADHD group were sensitive to the stress induced by ten headings, where plasma GFAP and UCH-L1 levels acutely increased after 10 headings. Variance in ADHD-specific verbal memory decline was correlated with increased levels of plasma GFAP in the ADHD group. Conclusions: These data suggest that ADHD may reduce brain tolerance to repetitive subconcussive head impacts.

Comparing Glial Fibrillary Acidic Protein (GFAP) in Serum and Plasma Following Mild Traumatic Brain Injury in Older Adults.

Objective: Identification and validation of blood-based biomarkers for the diagnosis and prognosis of mild traumatic brain injury (mTBI) is of critical importance. There have been calls for more research on mTBI in older adults. We compared blood-based protein marker glial fibrillary acidic protein (GFAP) concentrations in serum and in plasma within the same cohort of older adults and assessed their ability to discriminate between individuals based on intracranial abnormalities and functional outcome following mTBI.Methods: A sample of 121 older adults [≥50 years old with head computed tomography (CT), n = 92] seeking medical care for a head injury [Glasgow Coma Scale scores of 14 (n = 6; 5.0%) or 15 (n = 115; 95.0%)] were enrolled from the emergency department (ED). The mean time between injury and blood sampling was 3.4 h (SD = 2.1; range = 0.5–11.7). Serum GFAP concentration was measured first using the Human Neurology 4-Plex Assay, while plasma GFAP concentration was later measured using the GFAP Discovery Kit, both on an HD-1 Single molecule array (Simoa) instrument. Glasgow Outcome Scale-Extended was assessed 1 week after injury.Results: Both serum and plasma GFAP levels were significantly higher in those with abnormal CT scans compared to those with normal head CT scans (plasma: U = 1,198, p < 0.001; serum: U = 1,253, p < 0.001). The ability to discriminate those with and without intracranial abnormalities was comparable between serum (AUC = 0.814) and plasma (AUC = 0.778). In the total sample, GFAP concentrations were considerably higher in plasma than in serum (Wilcoxon signed-rank test z = 0.42, p < 0.001, r = 0.42). Serum and plasma GFAP levels were highly correlated in the total sample and within all subgroups (Spearman's rho range: 0.826–0.907). Both serum and plasma GFAP levels were significantly higher in those with poor compared to good functional outcome (serum: U = 1,625, p = 0.002; plasma: U = 1,539, p = 0.013). Neither plasma (AUC = 0.653) nor serum (AUC = 0.690) GFAP were adequate predictors of functional outcome 1 week after injury.Conclusions: Despite differences in concentration, serum and plasma GFAP levels were highly correlated and had similar discriminability between those with and without intracranial abnormalities on head CT following an mTBI. Neither serum nor plasma GFAP had adequate discriminability to identify patients who would have poor functional outcome.

Point-of-Care Platform Blood Biomarker Testing of Glial Fibrillary Acidic Protein versus S100 Calcium-Binding Protein B for Prediction of Traumatic Brain Injuries: A Transforming Research and Clinical Knowledge in Traumatic Brain Injury Study.

Glial fibrillary acidic protein (GFAP) is cleared by the Food and Drug Administration (FDA) to determine need for head computed tomography (CT) within 12 h after mild traumatic brain injury (TBI) (Glasgow Coma Score [GCS] 13-15); S100 calcium-binding protein B (S100B) serves this function in Europe. This phase 1 biomarker cohort analysis of the multi-center, observational Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study compares GFAP's diagnostic performance, measured on a rapid point-of-care platform, against protein S100B to predict intracranial abnormalities on CT within 24 h post-injury across the spectrum of TBI (GCS 3-15). Head CT scan performed in TBI subjects and blood was collected for all consenting subjects presenting to 18 United States level 1 trauma centers. Plasma was analyzed on a point-of-care device prototype assay for GFAP and serum was analyzed for S100B. In 1359 patients with TBI (GCS 3-15), mean (standard deviation [SD]) age = 40.1 (17.0) years; 68% were male. Plasma GFAP levels were significantly higher in CT+ TBI subjects (median = 1358 pg/mL, interquartile range [IQR]: 472-3803) than in CT- TBI subjects (median = 116 pg/mL, IQR: 26-397) or orthopedic trauma controls (n = 122; median = 13 pg/mL, IQR: 7-20), p < 0.001. Serum S100B levels were likewise higher in CT+ TBI subjects (median = 0.17 μg/L, IQR: 0.09-0.38) than in CT- TBI subjects (median = 0.10 μg/L, IQR: 0.06-0.18), p < 0.001. Receiver operating characteristic curves were generated for prediction of intracranial injury on admission CT scan; area under the curve (AUC) for GFAP was significantly higher than for S100B in the same cohort (GFAP AUC - 0.85, 95% confidence interval [CI] 0.83-0.87; S100B AUC - 0.67, 95% CI 0.64-0.70; p < 0.001). GFAP, measured on a point-of-care platform prototype assay, has high discriminative ability to predict intracranial abnormalities on CT scan in patients with TBI across the full injury spectrum of GCS 3-15 through 24 h post-injury. GFAP substantially outperforms S100B.

Plasma Markers of Neurodegeneration Are Raised in Friedreich's Ataxia.

Background: Friedreich’s ataxia (FRDA) is the most common autosomal recessive ataxia. Disease-modifying treatments are not available yet; however, several compounds are currently under investigation. As a result, there is a growing need for the identification of robust and easily accessible biomarkers for the monitoring of disease activity and therapeutic efficacy. The simultaneous measurement of multiple brain-derived proteins could represent a time- and cost-efficient approach for biomarker investigation in pathologically complex neurodegenerative diseases like FRDA.Objectives: To investigate the role of plasma neurofilament-light chain (NfL), glial fibrillary acidic protein (GFAP), total tau (t-tau) and ubiquitin C-terminal hydrolase L1(UCHL1) as biomarkers in FRDA. Additionally, NfL measurements derived from the novel multiplex assay were compared to those from an established NfL singleplex assay.Methods: In this study, an ultrasensitive Single molecule array (Simoa) 4-plex assay was used for the measurement of plasma NfL, GFAP, t-tau, and UCHL1 in 33 FRDA patients and 13 age-matched controls. Differences in biomarker concentrations between these groups were computed and associations with genetic and disease related parameters investigated. Additionally, the agreement between NfL measurements derived from the 4-Plex and an established Simoa NfL singleplex assay was assessed.Results: Mean plasma NfL, GFAP and UCHL1 levels were significantly higher in FRDA patients than in controls (NfL: p < 0.001; GFAP: p = 0.006, and UCHL1: p = 0.020). Conversely, there was no significant difference in concentrations of t-tau in the patient and control group (p = 0.236). None of the proteins correlated with the GAA repeat length or the employed measures of disease severity. The individual NfL values derived from the two assays showed a strong concordance (rc = 0.93). Although the mean difference of 1.29 pg/mL differed significantly from 0 (p = 0.006), regression analysis did not indicate the presence of a proportional bias.Conclusion: This is the first study demonstrating that NfL, GFAP, and UCHL1 levels are raised in FRDA, potentially reflecting ongoing neuronal degeneration and glial activation. Further studies are required to determine their role as marker for disease activity and progression. Furthermore, the novel 4-plex assay appears to be a valid tool to simultaneously measure brain-derived proteins at extremely low concentrations in the peripheral circulation.

Cardiopulmonary-Bypass Glial Fibrillary Acidic Protein Correlates With Neurocognitive Skills

Neurocognitive deficits at school starting age may affect as many as 50% of children who underwent cardiac surgery for complex congenital heart disease (CHD). The aim of this study was to identify which phases of cardiopulmonary bypass (CPB) are associated with an increased risk of impaired neurodevelopmental skills in children with complex CHD. This was assessed by means of glial fibrillary acidic protein (GFAP) plasma levels during CPB for CHD surgery, as a marker of neurologic insult. We correlated GFAP levels with clinical parameters and neurodevelopmental outcome. We studied 45 children undergoing surgery for complex CHD. We measured plasma GFAP levels by enzyme-linked immunosorbent assay at the following steps: anesthesia induction, CPB start, end of hypothermia, end of rewarming, and end of CPB. Neurologic assessment and Vineland Adaptive Behavior Scales (VABS-I) were administered to patients at least 18 months after surgery. GFAP was undetectable before surgery and it peaked at the end of hypothermia or rewarming. Multiple regression analyses showed that GFAP peak level and preoperative neurologic comorbidity were significant independent predictors of neurologic impairment, as showed by VABS-I communication domain intelligence quotient (IQ). Receiver operating characteristic curve showed that the model was highly significant. Impaired neurodevelopment was associated with increase of GFAP plasma levels during cardiac surgery in infants. The identification of the neurologic high-risk phases of CPB run could support the application of new neuroprotective strategies for CHD repair.

Serial Assessment of Gray Matter Abnormalities after Sport-Related Concussion.

There is an urgent need to characterize the acute physiological effects of sport-related concussion (SRC). We investigated the effects of SRC on gray matter structure and diffusion metrics in collegiate athletes at 1.64 (T1; n = 33), 8.33 (T2; n = 30), and 32.15 days (T3; n = 36) post-concussion, with healthy collegiate contact-sport athletes serving as controls (HA; n = 46). Plasma levels of glial fibrillary acidic protein (GFAP) were assessed in a subset of athletes. We hypothesized that acute SRC would be associated with increased fractional anisotropy (FA), decreased mean diffusivity (MD), and increased GFAP relative to noninjured HA, without acute differences in gray matter volume or cortical thickness. Further, we hypothesized that neither diffusion nor structure would show longitudinal changes across the first month post-SRC. Finally, we hypothesized that gray matter diffusion metrics would correlate with plasma GFAP levels, as indicated by pre-clinical literature. Consistent with our hypothesis, acute SRC was associated with decreased MD in the left pallidum, increased FA in the right amygdala, and a significantly greater number and volume of subject-specific clusters with increased FA compared to HA. No differences in gray matter volume, cortical thickness, or GFAP were observed between groups. There were no longitudinal changes in any measure across the first month post-SRC. Finally, FA in the right amygdala was inversely correlated with GFAP at T2. These results suggest that gray matter diffusion metrics may be useful in determining the physiological effects of SRC.

Comparison of GFAP and HSP27 concentrations in acute moderate-intensity aerobic exercise of different duration

Background: Glial fibrillary acidic protein (GFAP) and heat shock protein -27 (HSP27) plasma can be used as the parameters of exercise-induced astrocyte reactivity. The American College of Sports Medicine (ACSM) recommends an exercise of 30 minutes or 10 minutes duration (each performing bout accumulated toward 30 minutes). The aim of this study was to compare GFAP and HSP27 plasma concentrations in young adults undergoing acute moderate-intensity aerobic exercise of different durations (10 minutes vs 30 minutes).Methods: An experimental study with pre-post design was conducted on 22 participants assigned to either 10 minutes or 30 minutes duration of single bout exercise. Blood sampling was performed before and after the exercise. GFAP and HSP27 plasma levels were measured with ELISA methods. Plasma GFAP and HSP27 levels before and after exercise were analyzed using paired t -test, while GFAP and HSP27 levels after exercise between the two groups were processed using unpaired t-test.Results: Plasma GFAP concentration decreased significantly (0,45 ng/mL) after 30 minutes of aerobic exercise (p&lt;0.05). Plasma HSP27 concentration decreased significantly (1,71 ng/mL) after 10 minutes of aerobic exercise (p&lt;0.05). No significant difference in plasma GFAP and HSP27 concentrations between 10 minutes (GFAP=0.49 ng/mL; HSP27=2.09 ng/mL) and 30 minutes duration of exercise (GFAP=0.45 ng/mL; HSP27=1,71 ng/mL).Conclusion: Acute moderate-intensity aerobic exercise with 10- and 30-minutes duration reduces the reactivity of astrocytes indication the increase of the synapse plasticity. The decrease in GFAP concentration occurred after 30 minutes of exercise and the decrease in HSP27 occurred after 10 minutes of exercise. These results showed that the body responds differently to different treatment duration in order to obtain the same effect on the body.

Rewarming Rate During Cardiopulmonary Bypass Is Associated With Release of Glial Fibrillary Acidic Protein

Rewarming from hypothermia during cardiopulmonary bypass (CPB) may compromise cerebral oxygen balance, potentially resulting in cerebral ischemia. The purpose of this study was to evaluate whether CPB rewarming rate is associated with cerebral ischemia assessed by the release of the brain injury biomarker glial fibrillary acidic protein (GFAP). Blood samples were collected from 152 patients after anesthesia induction and after CPB for the measurement of plasma GFAP levels. Nasal temperatures were recorded every 15 min. A multivariate estimation model for postoperative plasma GFAP level was determined that included the baseline GFAP levels, rewarming rate, CPB duration, and patient age. The mean rewarming rate during CPB was 0.21° ± 0.11°C/min; the maximal temperature was 36.5° ± 1.0°C (range, 33.1°C to 38.0°C). Plasma GFAP levels increased after compared with before CPB (median, 0.022 ng/mL versus 0.035 ng/mL; p < 0.001). Rewarming rate (p = 0.001), but not maximal temperature (p = 0.77), was associated with higher plasma GFAP levels after CPB. In the adjusted estimation model, rewarming rate was positively associated with postoperative plasma log GFAP levels (coefficient, 0.261; 95% confidence intervals, 0.132 to 0.390; p < 0.001). Six patients (3.9%) experienced a postoperative stroke. Rewarming rate was higher (0.3° ± 0.09°C/min versus 0.2° ± 0.11°C/min; p = 0.049) in the patients with stroke compared with those without a stroke. Rewarming rate during CPB was correlated with evidence of brain cellular injury documented with plasma GFAP levels. Modifying current practices of patient rewarming might provide a strategy to reduce the frequency of neurologic complications after cardiac surgery.

The role of plasma GFAP as a biomarker for glioblastoma.

2095 Background: Magnetic resonance imaging (MRI) of the brain primarily assesses blood brain barrier (BBB) dysfunction which provides indirect information regarding tumor size. The limitations of MRI have become evident with the use of temozolomide (pseudo-progression) and VEGF based therapies (pseudo-response). As a result, a blood-based marker to assess tumor burden is increasingly important. Previous studies suggested that plasma glial fibrillary acidic protein (GFAP) levels are sensitive and specific for glioblastoma (GBM). This pilot study examines the utility of GFAP as a biomarker in pre- and post-operative gliomas. Methods: Plasma samples were collected in patients pre-operatively (N=34) and 24-48 hours post-operatively (N=24) for what was post-operatively confirmed to be newly diagnosed glioma. Plasma GFAP was detected using an electrochemiluminescent immunoassay with a detection threshold of >0.04ng/ml. Presence or absence of contrast enhancement (CE) on the pre-op MRI was compared with the pre-op plasma GFAP level using Fisher’s exact test. Results: The histologic, radiographic, and detection rates and pre- and post-op plasma GFAP levels are presented below. Higher grade tumors more often had CE on MRI than lower grade tumors (p=0.002). Plasma GFAP was detectable in 80% of patients with CE and 21% without CE (p=0.001). Conclusions: Higher grade tumors had more CE and higher plasma GFAP levels pre-operatively. However, post-operative GFAP levels dramatically increased in patients with lower grade gliomas that previously had undetectable levels. These data strongly suggest that GFAP is not a specific biomarker for GBM or an accurate measure of tumor burden. In addition, injury to the brain or BBB from surgery results in striking elevations of plasma GFAP independent of histologic grade or prior contrast enhancement. Histologic findings Contrast enhancement pre-op GFAP detectable pre-op GFAP levels pre-op median (range) GFAP detectable post-op GFAP levels post-op median (range) Grade 4 (n=9) 89% 100% 0.09 (0.07-0.15) 100% 0.07 (0.04-0.32) (N=5) Grade 3 (n=11) 55% 36% 0 (0-0.58) 100% 1.18 (0.11-4.56) (N=8) Grade 2 (n=14) 7% 21% 0 (0-0.22) 91% 0.38 (0.05-9.65) (N=11)

Plasma glial fibrillary acidic protein levels in children with sickle cell disease

To determine if glial fibrillary acidic protein (GFAP) is associated with brain injury in children with sickle cell disease (SCD), we measured plasma GFAP among cross-sectional groups of unselected children with SCD, subsets of children with SCD and normal brain MRI or MRI evidence of cerebral infarct, healthy pediatric controls, and adults with brain injury. Children with SCD had higher plasma GFAP than healthy pediatric controls (mean concentrations 0.14 ± 0.37 vs. 0.07 ± 0.08 ng/mL; P 5 0.003); also, 16.0% (16/100) of children with SCD and cerebral infarct had GFAP elevations above the 95th percentile of healthy pediatric controls (P 5 0.04). Although not statistically significant, children with SCD and cerebral infarct had more elevated GFAP levels than with SCD and no infarct (16/100, 16.0% vs. 14/168, 8.3%; P 5 0.07). Children with SCD and acute brain ischemia had a higher proportion of elevated GFAP than SCD children with normal MRI (3/6, 50% vs.8.3%; P 5 0.01). GFAP was associated with elevated systolic blood pressure in the preceding year and correlated positively with white blood cell count and negatively with age and performance IQ. Plasma GFAP is elevated among children with SCD and may be associated with subclinical brain injury.

Glial Fibrillary Acidic Protein as a Plasma Biomarker of Brain Injury in Children with Sickle Cell Disease.

Abstract 1512Poster Board I-535 IntroductionIn children with sickle cell disease (SCD), silent cerebral infarct (SCI) is an independent risk factor for lower IQ, poorer school performance, and overt stroke. MRI is the only method to identify patients with SCI. A blood biomarker of SCI in patients with sickle cell disease (SCD) would fill a clinical void because blood is easy to obtain and measure, a biomarker may determine risk of or progression of neurologic injury to overt stroke, and a biomarker could benchmark current and new therapies for SCI and other subclinical forms of neurologic injury in SCD. We hypothesized that an unbiased proteomics screen of plasma from sickle cell patients would yield biomarkers of brain injury. MethodsA cross-sectional sample of children 5-14 years old with sickle cell disease (HbSS and HbSB0) who were screened for the Silent Infarct Transfusion (SIT) Trial (ClinicalTrials.gov NCT00072761) were studied (n=258) along with 60 age-matched healthy controls and 28 adults with overt brain injury. For biomarker discovery, plasma underwent depletion of hemoglobin with nickel- nitrilotriacetic acid and immunoaffinity depletion of the 12 most abundant plasma proteins. After fractionation by reverse phase liquid chromatography over a C18 column and acetonitrile gradient and trypsin digestion, peptide spectra from each fraction were obtained by LC/MS/MS (LTQ-Orbitrap) and were searched using X!Tandem and human IPI database version 3.5. Post search analysis was performed using Proteomics Analysis Software System (Integrated Analysis Inc., Bethesda, MD). An electrochemiluminescent immunoassay was developed for one of the candidate proteins identified, glial fibrillary acidic protein (GFAP), for protein validation (MesoScale Discovery). ResultsGFAP, a brain-specific intermediate filament known to be a marker of acute stroke and head trauma in adults, was identified in discovery sample plasma. Four percent of sickle cell subjects in steady-state had plasma GFAP concentrations similar to stroke and brain surgery controls (>0.45 ng/mL). Among sickle cell subjects 5-14 years old screened for the SIT Trial, 9.3% had GFAP concentrations above the 95th percentile of age-matched controls (95th percentile cutoff: 0.227 ng/mL; p=0.08). Sickle cell subjects with silent cerebral infarct (SCI) had more elevations above the normal 95th percentile (10/69; 14.5%) than those without SCI (9/131; 6.8%), although this difference was not statistically significant (p=0.08). The sensitivity of GFAP as a marker of brain injury was demonstrated in a case of an 11 year-old child with HbSS and acute stroke in which plasma GFAP was 1.52 ng/mL (6 times the normal control 95th percentile) before the stroke was clinically evident and peaked at 2.83 ng/mL.We discovered GFAP as a circulating brain protein in plasma of children with SCD. Plasma GFAP is a marker of acute stroke in sickle cell disease but discriminates only minimally between SCI and non-SCI status in the SIT Trial using baseline cross-sectional samples. Four percent of children with sickle disease 5-14 years old have plasma GFAP levels similar to controls with severe brain injury without clinical evidence of overt stroke. ConclusionsElevations in circulating brain proteins such as GFAP show promise as indicators of subacute brain injury in children with SCI, but will require longitudinal studies of plasma GFAP in children with SCI to clarify the utility of GFAP as a plasma biomarker of SCI and a predictor of neurologic risk. DisclosuresNo relevant conflicts of interest to declare.