Glial Fibrillary Acidic Protein for Prehospital Diagnosis of Intracerebral Hemorrhage

Prehospital identification of intracerebral haemorrhage: a scoping review of early clinical features and portable devices

INTRODUCTION

Prehospital identification of intracerebral haemorrhage (ICH) in suspected stroke cases may enable the initiation of appropriate treatments and facilitate better-informed transport decisions. This scoping review aims to examine the literature to identify early clinical features and portable devices for the detection of ICH in the prehospital setting.

METHODS

Three databases were searched via Ovid (MEDLINE, EMBASE and CENTRAL) from inception to August 2022 using prespecified search strategies. One reviewer screened all titles, abstracts and full-text articles for eligibility, while a second reviewer independently screened 20% of the literature during each screening stage. Data extracted were tabulated to summarise the key findings.

RESULTS

A total of 6803 articles were screened for eligibility, of which 22 studies were included for analysis. Among them, 15 studies reported on early clinical features, while 7 considered portable devices. Associations between age, sex and comorbidities with the presence of ICH varied across studies. However, most studies reported that patients with ICH exhibited more severe neurological deficits (n=6) and higher blood pressure levels (n=11) at onset compared with other stroke and non-stroke diagnoses. Four technologies were identified for ICH detection: microwave imaging technology, volumetric impedance phase shift spectroscopy, transcranial ultrasound and electroencephalography. Microwave and ultrasound imaging techniques showed promise in distinguishing ICH from other diagnoses.

CONCLUSION

This scoping review has identified potential clinical features for the identification of ICH in suspected stroke patients. However, the considerable heterogeneity among the included studies precludes meta-analysis of available data. Moreover, we have explored portable devices to enhance ICH identification. While these devices have shown promise in detecting ICH, further technological development is required to distinguish between stroke subtypes (ICH vs ischaemic stroke) and non-stroke diagnoses.

Optimization of sensitivity and specificity of a biomarker-based blood test (LVOCheck-Opti): A protocol for a multicenter prospective observational study of patients suspected of having a stroke

Introduction

Acute ischemic stroke (AIS) is a time-critical medical emergency. For patients with large-vessel occlusions (LVO), mechanical thrombectomy (MT) is the gold-standard treatment. Mobile Stroke Units (MSUs) provide on-site diagnostic capabilities via computed tomography (CT) and have been shown to improve functional outcomes in stroke patients, but are cost-efficient only in urban areas. Blood biomarkers have recently emerged as possible alternative to cerebral imaging for LVO diagnosis. Prehospital LVO diagnosis offers the potential to transport patients directly to centers that have MT treatment available. In this study, we assess the accuracy of combining two biomarkers, HFABP and NT-proBNP, with clinical indicators to detect LVO using ultra-early prehospital blood samples. The study was registered in the German Clinical Trials Register (DRKS-ID: DRKS00030399).

Methods and analysis

We plan a multicenter prospective observational study with 800 patients with suspected stroke enrolled within 24 h of symptom onset. Study participants will be recruited at three sites (MSUs) in Berlin, Germany. Blood-samples will be taken pre-hospitally at the scene and tested for HFABP and NT-proBNP levels. Additional clinical data and information on final diagnosis will be collected and documented in an electronic case report form (eCRF). Sensitivity and specificity of the combination will be calculated through iterative permutation-response calculations.

Discussion

This study aims to evaluate the diagnostic capabilities of a combination of the biomarkers HFABP and NT-proBNP in LVO prediction. In contrast to most other biomarker studies to date, by employing MSUs as study centers, ultra-early levels of biomarkers can be analyzed. Point-of-care LVO detection in suspected stroke could lead to faster treatment in both urban and rural settings and thus improve functional outcomes on a broader scale.

Clinical trial registration

Deutsches Register klinischer Studien https://drks.de/search/de/trial/DRKS00030399, DRKS00030399.

Commentary on gaps in prehospital trauma care: education and bioengineering innovations to improve outcomes in hemorrhage and traumatic brain injury

Hemorrhage remains the leading cause of preventable death on the battlefield and the civilian arena. Many of these deaths occur in the prehospital setting. Traumatic brain injury also represents a major source of early mortality and morbidity in military and civilian settings. The inaugural HERETIC (HEmostatic REsuscitation and Trauma Induced Coagulopathy) Symposium convened a multidisciplinary panel of experts in prehospital trauma care to discuss what education and bioengineering advancements in the prehospital space are necessary to improve outcomes in hemorrhagic shock and traumatic brain injury. The panel identified several promising technological breakthroughs, including field point-of-care diagnostics for hemorrhage and brain injury and unique hemorrhage control options for non-compressible torso hemorrhage. Many of these technologies exist but require further advancement to be feasibly and reliably deployed in a prehospital or combat environment. The panel discussed shifting educational and training paradigms to clinical immersion experiences, particularly for prehospital clinicians. The panel discussed an important balance between pushing traditionally hospital-based interventions into the field and developing novel intervention options specifically for the prehospital environment. Advancing prehospital diagnostics may be important not only to allow more targeted applications of therapeutic options, but also to identify patients with less urgent injuries that may not need more advanced diagnostics, interventions, or transfer to a higher level of care in resource-constrained environments. Academia and industry should partner and prioritize some of the promising advances identified with a goal to prepare them for clinical field deployment to optimize the care of patients near the point of injury.

Palladium nanoclusters as a label to determine GFAP in human serum from donors with stroke by bimodal detection: inductively coupled plasma-mass spectrometry and linear sweep voltammetry

Water-soluble, stable, and monodisperse palladium nanoclusters (PdNCs) were synthesized using NaBH4 as a reductant and lipoic acid as a ligand. PdNCs, measured by high-resolution transmission electron microscopy, showed a round shape and a diameter of 2.49 ± 0.02 nm. It was found that each PdNC contains 550 Pd atoms on average. These PdNCs offer high amplification as a label of biochemical reactions when inductively coupled plasma-mass spectrometry (ICP-MS) is used as a detector. In addition, PdNCs have catalytic activity on electrochemical reactions, allowing detection by linear sweep voltammetry (LSV). As a proof of applicability, a competitive immunoassay based on PdNC labels was developed for the determination of glial fibrillary acidic protein (GFAP) in human serum, comparing ICP-MS and LSV detection. GFAP is a biomarker for differentiating between patients with ischemic stroke (IS) and hemorrhagic stroke (HS). The limit of detection (LoD), corresponding to IC10 (4-parameter logistic curve), was 0.03 pM of GFAP, both by ICP-MS and LSV, being lower than the 0.31 pM LoD provided by the ELISA commercial kit. Using the error profile method, 0.03 pM and 0.11 pM LoDs were obtained respectively by ICP-MS and LSV: LoD is lower by ICP-MS due to the better precision of the measurements. The analyses of human serum samples from IS, HS, and control (CT) donors using PdNC labels and detection by ICP-MS and LSV were validated with a commercial ELISA kit (for CT donors only ICP-MS provided enough sensitivity). Results point out toward the future use of PdNCs as a label in other immunoprobes for the determination of specific proteins requiring very low LoDs as well as the development of electrochemical decentralized methodologies.

Non-coding RNAs versus protein biomarkers to diagnose and differentiate acute stroke: Systematic review and meta-analysis

BACKGROUND

Stroke diagnosis is dependent on lengthy clinical and neuroimaging assessments, while rapid treatment initiation improves clinical outcome. Currently, more sensitive biomarker assays of both non-coding RNA- and protein biomarkers have improved their detectability, which could accelerate stroke diagnosis. This systematic review and meta-analysis compares non-coding RNA- with protein biomarkers for their potential to diagnose and differentiate acute stroke (subtypes) in (pre-)hospital settings.

METHODS

We performed a systematic review and meta-analysis of studies evaluating diagnostic performance of non-coding RNA- and protein biomarkers to differentiate acute ischemic and hemorrhagic stroke, stroke mimics, and (healthy) controls. Quality appraisal of individual studies was assessed using the QUADAS-2 tool while the meta-analysis was performed with the sROC approach and by assessing pooled sensitivity and specificity, diagnostic odds ratios, positive- and negative likelihood ratios, and the Youden Index.

SUMMARY OF REVIEW

112 studies were included in the systematic review and 42 studies in the meta-analysis containing 11627 patients with ischemic strokes, 2110 patients with hemorrhagic strokes, 1393 patients with a stroke mimic, and 5548 healthy controls. Proteins (IL-6 and S100 calcium-binding protein B (S100B)) and microRNAs (miR-30a) have similar performance in ischemic stroke diagnosis. To differentiate between ischemic- or hemorrhagic strokes, glial fibrillary acidic protein (GFAP) levels and autoantibodies to the NR2 peptide (NR2aAb, a cleavage product of NMDA neuroreceptors) were best performing whereas no investigated protein or non-coding RNA biomarkers differentiated stroke from stroke mimics with high diagnostic potential.

CONCLUSIONS

Despite sampling time differences, circulating microRNAs (< 24 h) and proteins (< 4,5 h) perform equally well in ischemic stroke diagnosis. GFAP differentiates stroke subtypes, while a biomarker panel of GFAP and UCH-L1 improved the sensitivity and specificity of UCH-L1 alone to differentiate stroke.

Blood-Based Biomarkers in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is one of the most lethal subtypes of stroke, associated with high morbidity and mortality. Prevention of hematoma growth and perihematomal edema expansion are promising therapeutic targets currently under investigation. Despite recent improvements in the management of ICH, the ideal treatments are still to be determined. Early stratification and triage of ICH patients enable the adjustment of the standard of care in keeping with the personalized medicine principles. In recent years, research efforts have been concentrated on the development and validation of blood-based biomarkers. The benefit of looking for blood candidate markers is obvious because of their acceptance in terms of sample collection by the general population compared to any other body fluid. Given their ease of accessibility in clinical practice, blood-based biomarkers have been widely used as potential diagnostic, predictive, and prognostic markers. This review identifies some relevant and potentially promising blood biomarkers for ICH. These blood-based markers are summarized by their roles in clinical practice. Well-designed and large-scale studies are required to validate the use of all these biomarkers in the future.

Molecular mechanisms of ischemia and glutamate excitotoxicity

Excitotoxicity is classically defined as the neuronal damage caused by the excessive release of glutamate, and subsequent activation of excitatory plasma membrane receptors. In the mammalian brain, this phenomenon is mainly driven by excessive activation of glutamate receptors (GRs). Excitotoxicity is common to several chronic disorders of the Central Nervous System (CNS) and is considered the primary mechanism of neuronal loss of function and cell death in acute CNS diseases (e.g. ischemic stroke). Multiple mechanisms and pathways lead to excitotoxic cell damage including pro-death signaling cascade events downstream of glutamate receptors, calcium (Ca2+) overload, oxidative stress, mitochondrial impairment, excessive glutamate in the synaptic cleft as well as altered energy metabolism. Here, we review the current knowledge on the molecular mechanisms that underlie excitotoxicity, emphasizing the role of Nicotinamide Adenine Dinucleotide (NAD) metabolism. We also discuss novel and promising therapeutic strategies to treat excitotoxicity, highlighting recent clinical trials. Finally, we will shed light on the ongoing search for stroke biomarkers, an exciting and promising field of research, which may improve stroke diagnosis, prognosis and allow better treatment options.

Unlocking the Potential of Stroke Blood Biomarkers: Early Diagnosis, Ischemic vs. Haemorrhagic Differentiation and Haemorrhagic Transformation Risk: A Comprehensive Review

Stroke, a complex and heterogeneous disease, is a leading cause of morbidity and mortality worldwide. The timely therapeutic intervention significantly impacts patient outcomes, but early stroke diagnosis is challenging due to the lack of specific diagnostic biomarkers. This review critically examines the literature for potential biomarkers that may aid in early diagnosis, differentiation between ischemic and hemorrhagic stroke, and prediction of hemorrhagic transformation in ischemic stroke. After a thorough analysis, four promising biomarkers were identified: Antithrombin III (ATIII), fibrinogen, and ischemia-modified albumin (IMA) for diagnostic purposes; glial fibrillary acidic protein (GFAP), micro RNA 124-3p, and a panel of 11 metabolites for distinguishing between ischemic and hemorrhagic stroke; and matrix metalloproteinase-9 (MMP-9), s100b, and interleukin 33 for predicting hemorrhagic transformation. We propose a biomarker panel integrating these markers, each reflecting different pathophysiological stages of stroke, that could significantly improve stroke patients' early detection and treatment. Despite promising results, further research and validation are needed to demonstrate the clinical utility of this proposed panel for routine stroke treatment.

Prospective collection of blood plasma samples to identify potential biomarkers for the prehospital stroke diagnosis (ProGrEss-Bio): study protocol for a multicenter prospective observational study

Introduction

Intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) are well-established, evidence-based, time-critical therapies that reduce morbidity and mortality in acute ischemic stroke (AIS) patients. The exclusion of intracerebral hemorrhage (ICH) is mandatory and has been performed by cerebral imaging to date. Mobile stroke units (MSUs) have been shown to improve functional outcomes by bringing cerebral imaging and IVT directly to the patient, but they have limited coverage. Blood biomarkers clearly distinguishing between AIS, ICH, and stroke mimics (SM) could provide an alternative to cerebral imaging if concentration changes are detectable in the hyperacute phase after stroke with high diagnostic accuracy. In this study, we will take blood samples in a prehospital setting to evaluate potential biomarkers. The study was registered in the German Clinical Trials Register (https://drks.de/search/de) with the identifier DRKS00023063.

Methods and analysis

We plan a prospective, observational study involving 300 patients with suspected stroke and symptom onset of ≤4.5 h before the collection of biomarkers. Study participants will be recruited from three sites in Berlin, Germany during MSU deployments. The focus of the study is the collection of blood samples from participants at the prehospital scene and from participants with AIS or ICH at a second-time point. All samples will be analyzed using targeted and untargeted analytical approaches. Study-related information about participants, including medical information and discharge diagnoses from the subsequent treating hospital, will be collected and documented in an electronic case report form (eCRF).

Discussion

This study will evaluate whether a single blood biomarker or a combination of biomarkers can distinguish patients with AIS and ICH from patients with stroke and SM in the early phase after symptom onset in the prehospital setting. In addition, the kinetics of blood biomarkers in AIS and ICH patients will be investigated. Our goal is to evaluate new ways to reliably diagnose stroke in the prehospital setting and thus accelerate the application of evidence-based therapies to stroke patients.

Monitoring risk and preventing ischemic stroke in the very old

INTRODUCTION

Stroke is a significant cause of death, and the leading cause of severe long-term disability for individuals over 80 (the very old), yet few studies of such risk factors for ischemic stroke, or the known mitigation techniques, in this population, and the evidence base regarding risk modification strategies in this susceptible population can be inconsistent and incomplete. This article examines current guidelines and evidence regarding medical management, lifestyle changes, and psychosocial interactions that can contribute to the primary and secondary prevention of ischemic stroke in the very old.

AREAS COVERED

The authors conducted a literature search for ischemic stroke prevention and risk assessment in the elderly via PubMed. Furthermore, they describe current strategies for monitoring risk and preventing ischemic stroke in the elderly population.

EXPERT OPINION

Ischemic stroke poses a significant health risk to the elderly, with prevention relying on managing modifiable risk factors such as hypertension, atrial fibrillation, diabetes, and high cholesterol, as well as promoting healthy lifestyle choices like quitting smoking, regular physical activity and a heart-healthy diet. Healthcare providers must adopt a multifaceted approach, addressing individual and population-level factors while remaining vigilant in monitoring and managing risk factors to reduce the incidence and impact of stroke in older adults.

Rapid Activation of Neuroinflammation in Stroke: Plasma and Extracellular Vesicles Obtained on a Mobile Stroke Unit

BACKGROUND

Neuroinflammation is ubiquitous in acute stroke and worsens outcome. However, the precise timing of the inflammatory response is unknown, hindering the design of acute anti-inflammatory therapeutic interventions. We sought to identify the onset of the neuroinflammatory cascade using a mobile stroke unit.

METHODS

The study is a proof-of-concept, cohort investigation of ultra-early blood- and extracellular vesicle-derived markers of neuroinflammation and outcome in acute stroke. Blood was obtained, prehospital, on an mobile stroke unit. Outcomes were biomarker concentrations, modified Rankin Scale score, and National Institutes of Health Stroke Scale score.

RESULTS

Forty-one adults were analyzed, including 15 patients treated on the mobile stroke unit between August 2021 and April 2022, and 26 healthy controls to establish biomarker reference levels. Median patient age was 74 (range, 36-97) years, 60% were female, and 80% White. Ten (67%) were diagnosed as stroke, with 8 (53%) confirmed and 2 likely transient ischemic attack or stroke averted by thrombolysis; 5 were stroke mimics. For strokes, median initial National Institutes of Health Stroke Scale score was 11 (range, 4-19) and 6 (75%) received tPA (tissue-type plasminogen activator). Blood was obtained a median of 58 (range, 36-133) minutes after symptom onset. Within 36 minutes after stroke, plasma IL-6 (interleukin-6), neurofilament light chain, UCH-L1 (ubiquitin C-terminal hydrolase L1), and GFAP (glial fibrillary acidic protein) were elevated by as much as 10 times normal. In EVs, MMP-9 (matrix metalloproteinase-9), CXCL4 (chemokine (C-X-C motif) ligand 4), CRP (C-reactive protein), IL-6, OPN (osteopontin), and PECAM1 (platelet and endothelial cell adhesion molecule 1) were elevated. Inflammatory markers increased rapidly in the first 2 hours and continued rising for 24 hours.

CONCLUSIONS

The neuroinflammatory cascade was found to be activated within 36 to 133 minutes after stroke and progresses rapidly. This is earlier than observed previously in humans and suggests injury from neuroinflammation occurs faster than had been surmised. These findings could inform development of acute immunomodulatory stroke therapies and lead to new diagnostic tools and improved outcomes.

Neurologic Biomarkers, Neuroimaging, and Cognitive Function in Persistent Atrial Fibrillation: A Cross-Sectional Study

The aim of this study was to evaluate the specific neurologic biomarkers, neuroimaging findings, and cognitive function in patients with persistent atrial fibrillation (AF) undergoing electrical cardioversion, compared to control subjects. This cross-sectional study included 25 patients with persistent AF undergoing electrical cardioversion and 16 age- and sex-matched control subjects. Plasma levels of glial fibrillary acidic protein (GFAP), neurofilament light protein (NFL), and ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), as well as parameters of neuroimaging and cognitive function, were compared between the groups. Neuroimaging was performed using the standard magnetic resonance imaging (MRI) protocol. Cognitive function was assessed using the Patient-Reported Outcomes Measurement Information System (PROMIS) Cognitive Function Index. Further analysis of neurologic biomarkers was performed based on the subsequent electrical cardioversion. There was no significant difference in GFAP (median of 24.7 vs. 28.7 pg/mL, p = 0.347), UCH-L1 (median of 112.8 vs. 117.7 pg/mL, p = 0.885), and NFL (median of 14.2 vs. 15.4 pg/mL, p = 0.886) levels between AF patients and control subjects. Similarly, neuroimaging showed no between-group difference in large cortical and non-cortical lesions (n = 2, 8.0% vs. n = 0, 0.0%, p = 0.246), small non-cortical lesions (n = 5, 20.0% vs. n = 5, 31.3%, p = 0.413), white matter hyperintensity (n = 23, 92.0% vs. n = 14, 87.5%, p = 0.636), and thromboembolic lesions (n = 0, 0.0% vs. n = 1, 6.3%, p = 0.206). Cognitive assessment did not show any between-group difference in the PROMIS index (52.2 ± 9.6 vs. 51.2 ± 6.2, p = 0.706). Finally, there were no significant dynamics in neurologic biomarkers following electrical cardioversion (p > 0.05). This hypothesis-generating study did not find a significant difference in neurologic biomarkers, neuroimaging findings, or cognitive function between patients with persistent AF and controls. The restoration of sinus rhythm was not significantly associated with a change in neurologic biomarkers. Further powered longitudinal studies are needed to re-assess these findings in an AF population.

Diagnostic performance of Glial Fibrillary Acidic Protein and Prehospital Stroke Scale for identification of stroke and stroke subtypes in an unselected patient cohort with symptom onset < 4.5 h

INTRODUCTION

Rapid identification and treatment of stroke is crucial for the outcome of the patient. We aimed to determine the performance of glial fibrillary acidic protein (GFAP) independently and in combination with the Prehospital Stroke Score (PreSS) for identification and differentiation of acute stroke within 4.5 h after symptom onset.

PATIENTS AND METHODS

Clinical data and serum samples were collected from the Treat-Norwegian Acute Stroke Prehospital Project (Treat-NASPP). Patients with suspected stroke and symptoms lasting ≤ 4.5 h had blood samples collected and were evaluated with the National Institutes of Health Stroke Scale prospectively. In this sub study, NIHSS was retrospectively translated into PreSS and GFAP was measured using the sensitive single molecule array (SIMOA).

RESULTS

A total of 299 patients with suspected stroke were recruited from Treat-NASPP and included in this study (44% acute ischemic stroke (AIS), 10% intracranial hemorrhage (ICrH), 7% transient ischemic attack (TIA), and 38% stroke mimics). ICrH was identified with a cross-fold validated area under the receiver-operating characteristic curve (AUC) of 0.73 (95% CI 0.62-0.84). A decision tree with PreSS and GFAP combined, first identified patients with a low probability of stroke. Subsequently, GFAP detected patients with ICrH with a 25.0% sensitivity (95% CI 11.5-43.4) and 100.0% specificity (95% CI 98.6-100.0). Lastly, patients with large-vessel occlusion (LVO) were detected with a 55.6% sensitivity (95% CI 35.3-74.5) and 82.4% specificity (95% CI 77.3-86.7).

CONCLUSION

In unselected patients with suspected stroke, GFAP alone identified ICrH. Combined in a decision tree, GFAP and PreSS identified subgroups with high proportions of stroke mimics, ICrH, LVO, and AIS (non-LVO strokes).

A magnetoimpedance biosensor microfluidic platform for detection of glial fibrillary acidic protein in blood for acute stroke classification

Acute stroke is the third leading cause of mortality and disability worldwide. Administration of appropriate therapy for acute stroke is critically dependent on timely classification into either ischemic or hemorrhagic subtypes, which have divergent treatment pathways. The current classification method is based on neuroimaging, which generally requires the transport of the patient to a hospital-based facility unless a mobile stroke unit is available. Plasma glial fibrillary acidic protein (GFAP) level has been identified as a useful blood-based biomarker to differentiate stroke subtypes. However, its conventional immunoassay methods are laboratory-based and time-consuming. Novel approaches for rapid stroke classification near the patients are urgently needed. Here, we report the development and testing of a microfluidic-based magnetoimpedance biosensor platform for measuring GFAP levels. The platform consists of a microfluidic chip for GFAP extraction from a blood sample and a magnetoimpedance (MI) biosensor that employs Dynabeads as a magnetic label to capture the GFAP molecules. We demonstrated the detection of recombinant GFAP protein in phosphate-buffered saline (PBS) and in mouse blood samples (detection limit 0.01 ng/mL) and of physiological GFAP in blood and plasma samples (detection limit 1.0 ng/mL) obtained from acute stroke patients. This detection level is within the range of cut-off levels required for clinical stroke subtype differentiation. This platform has the potential to be incorporated into a small device with further development to assist in the classification of acute stroke patients and clinical decision-making at the point-of-care.

Shifting acute stroke management to the prehospital setting

PURPOSE OF REVIEW

The earlier the treatment, the better the outcomes after acute ischemic stroke. Optimizing prehospital care bears potential to shorten treatment times. We here review the recent literature on mothership vs. drip-and-ship as well as mobile stroke unit concepts.

RECENT FINDINGS

Mobile stroke units result in the shortest onset-to-treatment times in mostly urban settings.

SUMMARY

Future research should focus on further streamlining processes around mobile stroke units, especially improving dispatch algorithms and improve referral for endovascular therapy.

Identifying patients with cerebral infarction within the time window compatible with reperfusion therapy, diagnostic performance of glutathione S-transferase-π (GST-π) and peroxiredoxin 1 (PRDX1): exploratory prospective multicentre study FLAG-1 protocol

INTRODUCTION

Plasma biomarkers may be useful in diagnosing acute cerebral infarction requiring urgent reperfusion, but their performance remains to be confirmed. If confirmed, these molecules could be used to develop rapid and reliable decentralised measurement methods, making it possible to initiate reperfusion therapy before hospital admission. The FLAG-1 large prospective study will constitute a plasma bank to assess the diagnostic performance of two biomarkers: glutathione S-transferase-π and peroxiredoxin 1. These molecules are involved in the oxidative stress response and could identify cerebral infarction within a therapeutic window of less than 4.5 hours following the onset of symptoms. Secondary objectives include assessing performance of these biomarkers within 3-hour and 6-hour windows; identifying additional biomarkers diagnosing cerebral infarction and significant criteria guiding therapeutic decisions: ischaemic features of stroke, presence of diffusion/fluid-attenuated inversion recovery mismatch, volume of cerebral infarction and penumbra on cerebral MRI.

METHODS AND ANALYSIS

The exploratory, prospective, multicentre FLAG-1 Study will include 945 patients with acute stroke symptoms (onset ≤12 hours, National Institute of Health Stroke Scale score ≥3). Each patient's 25 mL blood sample will be associated with cerebral MRI data. Two patient groups will be defined based on the time of blood collection (before and after 4.5 hours following onset). Receiver operating characteristic analysis will determine the diagnostic performance of each biomarker, alone or in combination, for the identification of cerebral infarction <4.5 hours.

ETHICS AND DISSEMINATION

The protocol has been approved by an independent ethics committee. Biological samples are retained in line with best practices and procedures, in accordance with French legislation. Anonymised data and cerebral imaging records are stored using electronic case report forms and a secure server, respectively, registered with the French Data Protection Authority (Commission Nationale de l'Informatique et des Libertés (CNIL)). Results will be disseminated through scientific meetings and publication in peer-reviewed medical journals.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT03364296).

Ultra-Early Differential Diagnosis of Acute Cerebral Ischemia and Hemorrhagic Stroke by Measuring the Prehospital Release Rate of GFAP

BACKGROUND

Plasma glial fibrillary acidic protein (GFAP) and tau are promising markers for differentiating acute cerebral ischemia (ACI) and hemorrhagic stroke (HS), but their prehospital dynamics and usefulness are unknown.

METHODS

We performed ultra-sensitivite single-molecule array (Simoa®) measurements of plasma GFAP and total tau in a stroke code patient cohort with cardinal stroke symptoms [National Institutes of Health Stroke Scale (NIHSS) ≥3]. Sequential sampling included 2 ultra-early samples, and a follow-up sample on the next morning.

RESULTS

We included 272 cases (203 ACI, 60 HS, and 9 stroke mimics). Median (IQR) last-known-well to sampling time was 53 (35-90) minutes for initial prehospital samples, 90 (67-130) minutes for secondary acute samples, and 21 (16-24) hours for next morning samples. Plasma GFAP was significantly higher in patients with HS than ACI (P < 0.001 for <1 hour and <3 hour prehospital samples, and <3 hour secondary samples), while total tau showed no intergroup difference. The prehospital GFAP release rate (pg/mL/minute) occurring between the 2 very early samples was significantly higher in patients with HS than ACI [2.4 (0.6-14.1)] versus 0.3 (-0.3-0.9) pg/mL/minute, P < 0.001. For cases with <3 hour prehospital sampling (ACI n = 178, HS n = 59), a combined rule (prehospital GFAP >410 pg/mL, or prehospital GFAP 90-410 pg/mL together with GFAP release >0.6 pg/mL/minute) enabled ruling out HS with high certainty (NPV 98.4%) in 68% of patients with ACI (sensitivity for HS 96.6%, specificity 68%, PPV 50%).

CONCLUSIONS

In comparison to single-point measurement, monitoring the prehospital GFAP release rate improves ultra-early differentiation of stroke subtypes. With serial measurement GFAP has potential to improve future prehospital stroke diagnostics .

Mobile Stroke Units: Current and Future Impact on Stroke Care

Ischemic stroke is a leading cause of death and major disability that impacts societies across the world. Earlier thrombolysis of blocked arteries with intravenous tissue plasminogen activator (tPA) and/or endovascular clot extraction is associated with better clinical outcomes. Mobile stroke units (MSU) can deliver faster tPA treatment and rapidly transport stroke patients to centers with endovascular capabilities. Initial MSU trials in Germany indicated more rapid tPA treatment times using MSUs compared with standard emergency room treatment, a higher proportion of patients treated within 60 minutes of stroke onset, and a trend toward better 3-month clinical outcomes with MSU care. In the United States, the first multicenter, randomized clinical trial comparing standard versus MSU treatment began in 2014 in Houston, TX, and has demonstrated feasibility and safety of MSU operations, reliability of telemedicine technology to assess patients for tPA eligibility without additional time delays, and faster door-to-groin puncture times of MSU patients needing endovascular thrombectomy in interim analysis. Scheduled for completion in 2021, this trial will determine the cost-effectiveness and benefit of MSU treatment on clinical outcomes compared with standard ambulance and hospital treatment. Beyond ischemic stroke, MSUs have additional clinical and research applications that can profoundly impact other cohorts of patients who require time-sensitive neurological care.

Intracerebral Hemorrhage with Intraventricular Extension Associated with Loss of Consciousness at Symptom Onset

BACKGROUND

In patients with spontaneous intracerebral hemorrhage (ICH), pre-hospital markers of disease severity might be useful to potentially triage patients to undergo early interventions.

OBJECTIVE

Here, we tested whether loss of consciousness (LOC) at the onset of ICH is associated with intraventricular hemorrhage (IVH) on brain computed tomography (CT).

METHODS

Among 3000 ICH cases from ERICH (Ethnic/Racial Variations of Intracerebral Hemorrhage study, NS069763), we included patients with complete ICH/IVH volumetric CT measurements and excluded those with seizures at ICH onset. Trained investigators extracted data from medical charts. Mental status at symptom onset (categorized as alert/oriented, alert/confused, drowsy/somnolent, coma/unresponsive/posturing) and 3-month disability (modified Rankin score, mRS) were assessed through standardized interviews of participants or dedicated proxies. We used logistic regression and mediation analysis to assess relationships between LOC, IVH, and unfavorable outcome (mRS 4-6).

RESULTS

Two thousand seven hundred and twenty-four patients met inclusion criteria. Median admission Glasgow Coma Score was 15 (interquartile range 11-15). 46% had IVH on admission or follow-up CT. Patients with LOC (mental status: coma/unresponsive, n = 352) compared to those without LOC (all other mental status, n = 2372) were younger (60 vs. 62 years, p = 0.005) and had greater IVH frequency (77 vs. 41%, p < 0.001), greater peak ICH volumes (28 vs. 11 ml, p < 0.001), greater admission systolic blood pressure (200 vs. 184 mmHg, p < 0.001), and greater admission serum glucose (158 vs. 127 mg/dl, p < 0.001). LOC was independently associated with IVH presence (odds ratio, OR, 2.6, CI 1.9-3.5) and with unfavorable outcome (OR 3.05, CI 1.96-4.75). The association between LOC and outcome was significantly mediated by IVH (beta = 0.24, bootstrapped CI 0.17-0.32).

CONCLUSION

LOC at ICH onset may be a useful pre-hospital marker to identify patients at risk of having or developing IVH.

Discriminative value of glial fibrillar acidic protein (GFAP) as a diagnostic tool in acute stroke. Individual patient data meta-analysis

Glial fibrillar acidic protein (GFAP) in serum has been evaluated as a promising biomarker to differentiate between intracerebral hemorrhage (ICH) and acute ischemic stroke (AIS). We assessed its value as diagnostic and prognostic tool for ICH through a literature systematic review and individual patient data (IPD) meta-analysis.We performed a systematic search in PubMed database until November 2018 for publications that evaluated GFAP to differentiate AIS and ICH within 4.5 hours after symptoms onset. Thereafter, we invited authors of selected studies to participate in this work by providing IPD from their cohorts. We used standardized individual subject's data to evaluate the association of GFAP concentrations with stroke subtype, demographics, stroke characteristics and factors related with GFAP measurement.From 4 selected studies, we collected data of 340 patients (236 AIS and 104 ICH). Standardized GFAP blood levels were significantly elevated in ICH compared with those with AIS (median and IQR: 0.84 (0.781-1.24), 0.79 (0.74-0.81); p<0.0001). In both stroke types, GFAP concentrations correlated with baseline stroke severity (r=0.27, p<0.0001; r=0.36, p<0.001; for AIS and ICH, respectively) but no correlation was found regarding time to sampling. Limited data precluded the evaluation of GFAP levels and functional outcome.These findings demonstrate substantially different levels of GFAP in the blood of patients with ICH compared with patients with AIS soon after the event, while no association was found with outcome. In summary, GFAP could be a valuable diagnostic tool to assist in medical decision-making and to optimize management of stroke in the acute setting.

Blood biomarkers for the diagnosis and differentiation of stroke: A systematic review and meta-analysis

Background

Correct diagnosis of stroke and its subtypes is pivotal in early stages for optimum treatment.

Aims

The aim of this systematic review and meta-analysis is to summarize the published evidence on the potential of blood biomarkers in the diagnosis and differentiation of stroke subtypes.

Methods

A literature search was conducted for papers published until 20 April 2020 in PubMed, EMBASE, Cochrane Library, TRIP, and Google Scholar databases to search for eligible studies investigating the role of blood biomarkers in diagnosing stroke. Quality assessment was done using modified Quality Assessment of Diagnostic Accuracy Studies questionnaire. Pooled standardized mean difference and 95% confidence intervals were calculated. Presence of heterogeneity among the included studies was investigated using the Cochran's Q statistic and I2 metric tests. If I2 was < 50% then a fixed-effect model was applied else a random-effect model was applied. Risk of bias was assessed using funnel plots and between-study heterogeneity was assessed using meta-regression and sensitivity analyses. Entire statistical analysis was conducted in STATA version 13.0.

Results

A total of 40 studies including patients with 5001 ischemic strokes, 756 intracerebral hemorrhage, 554 stroke mimics, and 1774 healthy control subjects analyzing 25 biomarkers (within 24 h after symptoms onset/after the event) were included in our meta-analysis; 67.5% of studies had moderate evidence of quality. Brain natriuretic peptide, matrix metalloproteinase-9, and D-dimer significantly differentiated ischemic stroke from intracerebral hemorrhage, stroke mimics, and health control subjects ( p < 0.05). Glial fibrillary acidic protein successfully differentiated ischemic stroke from intracerebral hemorrhage (standardized mean difference −1.04; 95% confidence interval −1.46 to −0.63) within 6 h. No studies were found to conduct a meta-analysis of blood biomarkers differentiating transient ischemic attack from healthy controls and stroke mimics.

Conclusion

This meta-analysis highlights the potential of brain natriuretic peptide, matrix metalloproteinase-9, D-dimer, and glial fibrillary acidic protein as diagnostic biomarkers for stroke within 24 h. Results of our meta-analysis might serve as a platform for conducting further targeted proteomics studies and phase-III clinical trials. PROSPERO Registration ID: CRD42019139659.

A scoping review of pre-hospital technology to assist ambulance personnel with patient diagnosis or stratification during the emergency assessment of suspected stroke

BACKGROUND

Pre-hospital identification of key subgroups within the suspected stroke population could reduce delays to emergency treatment. We aimed to identify and describe technology with existing proof of concept for diagnosis or stratification of patients in the pre-hospital setting.

METHODS

A systematic electronic search of published literature (from 01/01/2000 to 06/06/2019) was conducted in five bibliographic databases. Two reviewers independently assessed eligibility of studies or study protocols describing diagnostic/stratification tests (portable imaging/biomarkers) or technology facilitating diagnosis/stratification (telemedicine) used by ambulance personnel during the assessment of suspected stroke. Eligible descriptions required use of tests or technology during the actual assessment of suspected stroke to provide information directly to ambulance personnel in the pre-hospital setting. Due to study, intervention and setting heterogeneity there was no attempt at meta-analysis.

RESULTS

2887 articles were screened for eligibility, 19 of which were retained. Blood biomarker studies (n = 2) were protocols of prospective diagnostic accuracy studies, one examining purines and the other a panel of known and novel biomarkers for identifying stroke sub-types (versus mimic). No data were yet available on diagnostic accuracy or patient health outcomes. Portable imaging studies (n = 2) reported that an infrared screening device for detecting haemorrhages yielded moderate sensitivity and poor specificity in a small study, whilst a dry-EEG study to detect large vessel occlusion in ischaemic stroke has not yet reported results. Fifteen evaluations of pre-hospital telemedicine were identified (12 observational and 3 controlled comparisons) which all involved transmission of stroke assessment data from the pre-hospital setting to the hospital. Diagnosis was generally comparable with hospital diagnosis and most telemedicine systems reduced time-to-treatment; however, it is unknown whether this time saving translated into more favourable clinical outcomes. Telemedicine systems were deemed acceptable by clinicians.

CONCLUSIONS

Pre-hospital technologies to identify clinically important subgroups amongst the suspected stroke population are in development but insufficient evidence precludes recommendations about routine use in the pre-hospital setting. Multi-centre diagnostic accuracy studies and clinical utility trials combining promising technologies are warranted.

Blood Biomarkers for Stroke Diagnosis and Management

Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment and predict outcomes. Many blood biomarkers already guide decision-making in clinical practice. In stroke, the number of candidate biomarkers is constantly increasing. These biomarkers include proteins, ribonucleic acids, lipids or metabolites. Although biomarkers have the potential to improve the diagnosis and the management of patients with stroke, there is currently no marker that has demonstrated sufficient sensitivity, specificity, rapidity, precision, and cost-effectiveness to be used in the routine management of stroke, thus highlighting the need for additional work. A better standardization of clinical, laboratory and statistical procedures between centers is indispensable to optimize biomarker performance. This review focuses on blood biomarkers that have shown promise for translation into clinical practice and describes some newly reported markers that could add to routine stroke care. Avenues for the discovery of new stroke biomarkers and future research are discussed. The description of the biomarkers is organized according to their expected application in clinical practice: diagnosis, treatment decision, and outcome prediction.

Blood Level of Glial Fibrillary Acidic Protein (GFAP) Does not Correlate With Disease Progression in a Rat Model of Familial ALS (SOD1G93A Transgenic)

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by specific loss of motor neurons in the spinal cord and brain stem. Currently, there are limited options for treating ALS and further investigation of the disease etiology and ALS disease progression need to be completed. There is an urgent need to identify biomarkers to detect and study disease progression in ALS. Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is expressed by a number of cells related to the central nervous system including glial cells and ependymal cells. Recent studies indicated that significant levels of GFAP protein were detected in peripheral tissues, such as skeletal muscle. In this study, we hypothesized that levels of GFAP in blood represent a biomarker of disease progression in ALS. To test this specific hypothesis, we used a rat model of familial ALS (SOD1^G93A transgenic), which has been extensively used to understand the complexity of this devastating disease. Disease progression in a cohort of male and female SOD1^G93A transgenic rats was monitored by motor function, and blood samples were collected when these animals reached disease end-stage. We measured GFAP protein levels by ELISA and found no correlation between GFAP concentration and disease progression in either serum and plasma samples of SOD1^G93A transgenic. Further investigation would be required in order to implicate blood GFAP as a potential biomarker for ALS.

Glial fibrillary acidic protein for the early diagnosis of intracerebral hemorrhage: Systematic review and meta-analysis of diagnostic test accuracy

Background and aims

Glial fibrillary acidic protein (GFAP) has shown promise in several studies for its ability to diagnose intracerebral hemorrhage (ICH). We evaluated the diagnostic accuracy of blood GFAP level to differentiate (ICH) from acute ischemic stroke (AIS) and stroke mimics, both overall, and in the first three hours after symptom onset.

Methods

We searched multiple databases, without language restriction, from inception until December 2017. Hierarchical summary receiver operating characteristic (HSROC) modeling was used to meta-analyze results. We conducted subgroup analyses restricted to blood samples collected within 0–60, 60–120, and 120–180 min time groups after symptom onset, to evaluate diagnostic accuracy in the early pre-hospital phase. Between and within study heterogeneity was explored using meta-regression.

Results

The search identified 199 potentially relevant citations from which 11 studies involving 1297 participants (350 ICH, 947 AIS, or mimic) were included. The pooled sensitivity, specificity, and area under the HSROC curve were 0.756 (95% CI 0.630–0.849), 0.945 (95% CI 0.858–0.980), and 0.904 (95% CI 0.878–0.931), respectively. Differences in assays used, but not the other covariates, partially explained between-study heterogeneity ( p = 0.034). The summary estimates for the 0–60, 60–120, and 120–180 min subgroups were comparable to the primary analysis and there was no statistically significant difference in diagnostic accuracy between subgroups.

Conclusions

GFAP is a promising diagnostic biomarker for ICH diagnosis in the early pre-hospital phase. Test accuracy is affected by assay subtype, but there are still unexplained sources of heterogeneity. High quality, international multi-center trials are warranted to develop and validate a point-of-care GFAP assay for the rapid triage and evaluation of acute stroke in the pre-hospital setting.

Glial fibrillary acidic protein as a prognostic marker of acute ischemic stroke

Background:

We investigated the association between serum levels of glial fibrillary acidic protein (GFAP) and stroke functional outcomes in a cohort of 286 patients with acute ischemic stroke (AIS).

Methods:

We prospectively studied 286 patients with AIS who were admitted within 24 h after the onset of symptoms. Serum levels of GFAP and National Institutes of Health Stroke Scale (NIHSS) were measured at admission. The primary end point was stroke functional outcome among 1-year after stroke onset. We used logistic regression models to assess the relationship between GFAP levels and stroke outcomes.

Results:

The GFAP level was obtained with a median value of 0.18 (interquartile ranges (IQRs): 0.09–0.28) ng/ml. In multivariable models adjusted for age, gender, and other risk factors, GFAP levels were associated with an increased risk of a NIHSS>6 (odds ratio (OR) = 1.55; 95% confidence interval (CI): 1.16–1.89; p = 0.012). The poor outcome distribution across the GFAP quartiles ranged between 12.7% (first quartile) and 70.4% (fourth quartile). After adjusting for other established risk factors, in multivariate models comparing the Q3 and Q 4 quartiles against the Q1 of the GFAP, the levels of GFAP were associated with poor outcome, and the adjusted risk of poor outcome increased by 211% (3.11[1.80–5.05], p < 0.001) and 522% (6.22[2.98–11.83], p < 0.001), respectively. Interestingly, GFAP improved the ability of NIHSS score to diagnose poor outcomes (area under the curve [AUC] of the combined model 0.82; 95% CI: 0.77–0.88; p = 0.02).

Conclusion:

GFAP levels are a novel and complementary biomarker to predict functional outcome 1 year after AIS

Derivation of a Three Biomarker Panel to Improve Diagnosis in Patients with Mild Traumatic Brain Injury

Background

Nearly 5 million emergency department (ED) visits for head injury occur each year in the United States, of which <10% of patients show abnormal computed tomography (CT) findings. CT negative patients frequently suffer protracted somatic, behavioral, and neurocognitive dysfunction. Our goal was to evaluate biomarkers to identify mild TBI (mTBI) in patients with suspected head injury.

Methods

An observational ED study of head-injured and control patients was conducted at Johns Hopkins University (HeadSMART). Head CT was obtained (ACEP criteria) in patients with Glasgow Coma Scale scores of 13–15 and aged 18–80. Three candidate biomarker proteins, neurogranin (NRGN), neuron-specific enolase (NSE), and metallothionein 3 (MT3), were evaluated by immunoassay (samples <24 h from injury). American Congress of Rehabilitation Medicine (ACRM) criteria were used for diagnosis of mTBI patients for model building. Univariate analysis, logistic regression, and random forest (RF) algorithms were used for data analysis in R. Overall, 662 patients were studied. Statistical models were built using 328 healthy controls and 179 mTBI patients.

Results

Median time from injury was 5.9 h (IQR, 4.0; range 0.8–24 h). mTBI patients had elevated NSE, but decreased MT3 versus controls (p < 0.01 for each). NRGN was also elevated but within 2–6 h after injury. In the derivation set, the best model to distinguish mTBI from healthy controls used three markers, age, and sex as covariates (C-statistic = 0.91, sensitivity 98%, specificity 72%). Panel test accuracy was validated with the 155 remaining ACRM+ mTBI patients. Applying the RF model to the ACRM+ mTBI validation set resulted in 78% correctly classified as mTBI (119/153). CT positive and CT negative validation subsets were 91% and 75% correctly classified. In samples taken <2 h from injury, 100% (10/10) samples classified correctly, indicating that hyperacute testing is possible with these biomarker assays. The model accuracy varied from 72–100% overall, and had greater accuracy with increasing severity, as shown by comparing CT+ with CT− (91% versus 75%), and Injury Severity Score ≥16 versus <16 (88% versus 72%, respectively). Objective blood tests, detecting NRGN, NSE, and MT3, can be used to identify mTBI, irrespective of neuroimaging findings.

The PRE-hospital Stroke Treatment Organization

Background

The PRE-hospital Stroke Treatment Organization was formed in 2016 as an international consortium of medical practitioners involved in pre-hospital treatment of patients with acute stroke.

Aims

PRE-hospital Stroke Treatment Organization’s mission is to improve stroke outcomes by supporting research and advocacy for pre-hospital stroke treatment in Mobile Stroke Units. PRE-hospital Stroke Treatment Organization will provide a platform to enhance collaborative research across the spectrum of acute stroke management in the pre-hospital setting. PRE-hospital Stroke Treatment Organization will also facilitate the appropriate proliferation and distribution of Mobile Stroke Units by providing a forum for professional communication, resource for public education, and stimulus for government, industry, and philanthropic support.

Summary of review

In this “white paper”, we describe the evidence supporting pre-hospital stroke treatment, progress to date, practical issues such as application in various environments and staffing, planned research initiatives, and organizational structure.

Conclusions

PRE-hospital Stroke Treatment Organization is not-for-profit, with membership open to anyone involved (or hoping to become involved) in pre-hospital stroke care. PRE-hospital Stroke Treatment Organization has a Steering Committee comprised of members from Europe, U.S., Canada, Australia, and other regions having a Mobile Stroke Unit in operation. PRE-hospital Stroke Treatment Organization convenes satellite meetings for membership at the International Stroke Conference and European Stroke Congress each year to address the PRE-hospital Stroke Treatment Organization mission. The first research collaborations agreed upon are to: (1) develop a list of common data elements to be collected by all Mobile Stroke Unit programs and entered into a common research database, and (2) develop a protocol for investigating the natural history of hyper-acute Intracerebral Hemorrhage.

Plasma Glial Fibrillary Acidic Protein in the Differential Diagnosis of Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Plasma GFAP (glial fibrillary acidic protein) has recently emerged as a potential biomarker for the differentiation of acute intracerebral hemorrhage (ICH) from acute ischemic stroke (AIS). We prospectively assessed the diagnostic accuracy of GFAP in the differential diagnosis of ICH.

METHODS

Consecutive patients presenting to the emergency department within 6 hours from symptom onset were evaluated. All patients underwent extensive diagnostic work-up and were classified according to discharge diagnosis in AIS, ICH, subarachnoid hemorrhage, and stroke mimics. GFAP was also measured in healthy volunteers (controls). Baseline stroke severity was evaluated using National Institutes of Health Stroke Scale. Receiver operating characteristic curve analysis was used to identify the optimal cutoff point for the differentiation between subgroups. Correlation analyses of GFAP plasma concentrations with baseline National Institutes of Health Stroke Scale and onset to sampling time were performed with the nonparametric Spearman rank test and fractional polynomial regression, respectively.

RESULTS

Our study population consisted of 270 individuals (AIS: 121, ICH: 34, stroke mimics: 31, subarachnoid hemorrhage: 5, controls: 79). No differences on baseline stroke severity and onset to sampling time were detected between AIS and ICH. Higher median plasma GFAP values were documented in ICH compared with AIS, stroke mimics, and controls (P<0.001). Receiver operating characteristic analysis highlighted a cutoff value of 0.43 ng/mL as the optimal threshold for the differentiation between ICH and AIS (sensitivity: 91%, specificity: 97%). No association was detected between plasma GFAP concentrations and baseline stroke severity for both AIS (P=0.515) and ICH (P=0.387). In the fractional polynomial analysis, the association between GFAP concentration and onset to sampling time was best described by a J-shaped curve for AIS and an inverted U-shaped curve for ICH, with a peak at 2 hours.

CONCLUSIONS

Plasma GFAP seems to be a sensitive and specific biomarker for the differentiation of ICH from both AIS and other acute neurological disorders, with the optimal diagnostic yield being present in the second hour from symptom onset.

A Refined Bead-Free Method to Identify Astrocytic Exosomes in Primary Glial Cultures and Blood Plasma

Astrocytes are the most abundant glial cell type in the central nervous system (CNS) and are known to fulfill critical homeostatic functions. Dysfunction of activated astrocytes is also known to participate in the development of several neurological diseases. Astrocytes can be uniquely identified by expression of the intermediate filament protein glial acidic fibrillary protein (GFAP). Herein, we report on the development of a rigorous and sensitive methodology to identify GFAP+ exosomes in primary culture using flow cytometry. We then demonstrate that activated astrocytes release increased amounts of exosomes in response to treatment with interleukin-1β. Using this methodology, we report the identification of GFAP+ exosomes in blood and then use a mouse model of inflammatory demyelination, experimental autoimmune encephalomyelitis (EAE), to examine whether the abundance of GFAP+ exosomes in blood circulation changes during clinical illness. We find a detectable increase in the presence of GFAP+ exosomes in EAE mice when compared with non-EAE, control mice. Our data provide a novel perspective on the presence of GFAP in blood as it identifies exosomes as potential astrocyte-derived signals within blood. These data are complementary to previous clinical studies that reported elevated GFAP protein in blood samples from multiple sclerosis (MS) patients during a clinical relapse. These data also reveal the existence of a potential systemic role for astrocyte-derived exosomes in CNS conditions involving inflammation such as multiple sclerosis.