Establishment of reference values for plasma neurofilament light based on healthy individuals aged 5–90 years

Associations of Plasma Neurofilament Light Levels With Brain Microstructure and Macrostructure and Cognition in the Community-Based Rhineland Study

BACKGROUND AND OBJECTIVES

Plasma neurofilament light chain (NfL) level is a sensitive yet aspecific marker of neurodegeneration. Its neuroanatomical and functional correlates in the general population are not fully elucidated. We thus assessed how brain's macrostructures and microstructures and cognitive function are related to plasma NfL levels in cognitively unimpaired adults over a wide age range.

METHODS

Our analyses were based on cross-sectional data from the Rhineland Study, a community-based prospective cohort study. This study includes people from the age of 30 onwards who live in 2 geographically defined areas in Bonn, Germany, and have sufficient command of the German language. Plasma NfL levels were measured using the Simoa platform and then log-transformed and adjusted for plate position, batch number, and Analyzer (HD-1 or HD-X). Brain imaging data were collected on a 3 Tesla scanner and included volumetric measures, metrics of the diffusion tensor and the neurite orientation dispersion and density imaging model, and white matter hyperintensity load. Memory performance, processing speed, and executive function were assessed using traditional cognitive tasks and an eye movement battery. We used multivariable regression models to assess the relations between brain structure and plasma NfL levels and between plasma NfL levels and cognitive performance.

RESULTS

The study sample consisted of 5,589 participants aged 30-95 years (mean age 55 ± 13.7 years, 56.1% women) without neurodegenerative diseases. Higher plasma NfL levels were associated with lower isotropic volume fraction (-0.030; 95% CI -0.051 to -0.010; pFDR = 0.011), lower neurite density index (ß = -0.031; 95% CI -0.053 to -0.008; pFDR = 0.014), and higher axial diffusivity (ß = 0.037; 95% CI 0.013-0.062; p = 0.005; pFDR = 0.011). The strongest association was with the orientation dispersion index (ß = -0.063; 95% CI -0.085 to -0.041; pFDR < 0.001). Furthermore, higher plasma NfL levels tended to be associated with a lower processing speed domain score (ß = -0.046; 95% CI -0.084 to -0.009; p = 0.014; pFDR = 0.056) and longer prosaccade latency (ß = 0.039; 95% CI 0.000-0.078; p = 0.049; pFDR = 0.480).

DISCUSSION

Higher plasma NfL levels mainly reflect worse white matter microstructural integrity, especially lower axonal density, in a relatively healthy, community-based sample. This suggests that plasma NfL levels allow for early detection of subtle differences in brain microstructure.

Biofluid biomarkers in distinguishing young-onset dementia from primary psychiatric disorders

PURPOSE OF REVIEW

There has been growing interest in the role of biofluid biomarkers to aid the diagnosis of dementia in older people. However, less attention has been given to younger people who have dementia (young-onset dementia), who frequently experience misdiagnoses of primary psychiatric disorders diagnostic delay and challenges accessing appropriate care.

RECENT FINDINGS

We describe 12 studies from the previous 2 years of which the majority have investigated the role of neurofilament light chain protein (NfL) in blood and cerebrospinal fluid in distinguishing young-onset dementia from primary psychiatric disorders. Synaptic and astrocytic biomarkers were also investigated. Sample sizes ranged from n = 46 to n = 999 and studies were mostly from Australia and the Netherlands.

SUMMARY

The major finding from this review was that NfL has very high sensitivity and specificity in differentiating a range of young-onset dementias (Alzheimer's dementia, behavioural-variant frontotemporal dementia) from PPD (schizophrenia, bipolar affective and major depressive disorders). NfL is easily accessible via the blood, so there is significant potential that a blood test could be available to make this dichotomisation. Further research is required to support clinical translation such as changes of NfL with disease progression and standardising analytic techniques.

Serum NFL and neuropsychological performance over ∼8 years in women with and without HIV: a longitudinal repeated measures study

Background

Blood-based biomarkers of Alzheimer's disease (AD) and stroke, including serum neurofilament light chain (sNFL), are understudied in women living with and without HIV.

Methods

We assessed cross-sectional and longitudinal change in sNFL between 2008 and 2019 associated with neuropsychological performance (NP) among women living with HIV (WLWH) and without HIV (WLWOH) age ≥40 years in the Women's Interagency HIV Study. Baseline and repeated ∼8-year fasting sNFL levels were measured using Simoa. Sociodemographically-adjusted NP T-scores (attention, working memory, executive function, processing speed, learning, verbal fluency and global) were calculated. Multivariable linear regression analyses stratified by HIV serostatus examined cross-sectional baseline and follow-up associations, and ∼8-year change in sNFL level related to global and domain-specific NP T-scores.

Findings

417 participants (290 WLWH, 127 WLWOH), African American/Black (55%), ≥high school education (69%), current/former smokers (79%), and overweight/obese (BMI ≥25.0 kg/m2, 74%) were included. Compared to WLWOH at baseline, WLWH performed worse on memory and global NP. WLWH versus WLWOH had higher baseline (p ≤ 0.001) and follow-up median (p < 0.0001) sNFL levels and ∼8-year change (46.5% in WLWH versus 24.4% in WLWOH, p < 0.0001). Among WLWH, higher baseline sNFL was associated with poorer processing speed, learning, memory and verbal fluency. Among WLWOH, higher baseline sNFL was associated with poorer executive function, processing speed and verbal fluency. Among WLWH, higher follow-up sNFL was associated with poorer executive function. Among WLWOH, higher follow-up sNFL was associated with poorer executive function, processing speed, attention, memory, and global NP. ∼8-year increase in sNFL occurred in both WLWH and WLWOH and was associated with poorer executive function, processing speed, memory, and global performance at follow-up among WLWOH, and poorer executive function in WLWH. Adjustment for multiple comparisons showed associations at cross-sectional follow-up and ∼8-year increase in sNFL in WLWOH, only. Higher sNFL was associated with poorer baseline processing speed in WLWH only.

Interpretation

Higher levels and greater ∼8-year increases in sNFL were associated with poorer NP by domain in WLWH and WLWOH differentially over time.

Funding

The contents of this publication are solely the responsibility of the authors and do not represent the official views of the National Institutes of Health (NIH). MACS/WIHS Combined Cohort Study (MWCCS) (Principal Investigators: Bronx CRS (Kathryn Anastos, David Hanna, and Anjali Sharma), U01-HL146204; Brooklyn CRS (Deborah Gustafson and Tracey Wilson), U01-HL146202; Data Analysis and Coordination Center (Gypsyamber D'Souza, Stephen Gange and Elizabeth Topper), U01-HL146193; Chicago-Cook County CRS (Mardge Cohen and Audrey French), U01-HL146245; Northern California CRS (Bradley Aouizerat, Jennifer Price, and Phyllis Tien), U01-HL146242; Metropolitan Washington CRS (Seble Kassaye and Daniel Merenstein), U01-HL146205. The MWCCS is funded primarily by the National Heart, Lung, and Blood Institute (NHLBI), with additional co-funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institute on Aging (NIA), National Institute of Dental and Craniofacial Research (NIDCR), National Institute of Allergy and Infectious Diseases (NIAID), National Institute of Neurological Disorders and Stroke (NINDS), National Institute of Mental Health (NIMH), National Institute on Drug Abuse (NIDA), National Institute of Nursing Research (NINR), National Cancer Institute (NCI), National Institute on Alcohol Abuse and Alcoholism (NIAAA), National Institute on Deafness and Other Communication Disorders (NIDCD), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institute on Minority Health and Health Disparities (NIMHD), and in coordination and alignment with the research priorities of the National Institutes of Health, Office of AIDS Research (OAR). MWCCS data collection is also supported by UL1-TR000004 (UCSF CTSA), UL1-TR003098 (JHU ICTR), UL1-TR001881 (UCLA CTSI).

Phenotypic and oncological insights in ANNA1 autoimmunity: Age stratification and biomarker analysis

OBJECTIVE

To describe the phenotypes, oncological associations, biomarker profiles, and outcomes across different age groups in patients with ANNA1 (anti-Hu) autoimmunity.

METHODS

A retrospective review of patients with ANNA1-IgG in serum/CSF between January 1, 2001, and December 31,2019 was performed. Patients were classified into three groups based on the age of symptom onset. Phage immunoprecipitation sequencing (PhIP-Seq) and neurofilament light chain (NfL) measurements were done in patient sera/CSF with archived samples.

RESULTS

Of 122 patients, 81 (66%), 20 (16%), and 21 (17%) patients belonged to older adults, young adults, and pediatric groups, respectively. Lung cancer and neuromuscular presentations were more common in older adults (p < 0.001), while limbic encephalitis and neuroblastoma were more common in pediatric patients (p < 0.005). Most young adults (75%) did not have cancer identified. Proportions of patients with a favorable response to immunotherapy were 20%, 30%, and 52% among older adults, young adults, and pediatric groups, respectively. PhIP-Seq demonstrated significant enrichment for ELAVL4 peptides especially for amino acids 240-289, in the majority of samples evaluated (36/67, 54%). ZIC and SOX2 peptides were significantly enriched in those with central nervous system presentations. Serum NfL levels were elevated in patients with cancer and those with poor long-term outcomes.

INTERPRETATION

Young adults with ANNA1 autoimmunity phenotypically resembled older adults but rarely had an underlying cancer. Pediatric patients frequently presented with limbic encephalitis and neuroblastoma and often responded favorably to immunotherapy. Distinct antigenic signatures may underlie differences in clinical presentations. Serum NfL levels may be a biomarker of poor long-term outcomes in ANNA1 autoimmunity.

Blood biomarker profiles in young-onset neurocognitive disorders: A cohort study

INTRODUCTION

Young-onset neurocognitive symptoms result from a heterogeneous group of neurological and psychiatric disorders which present a diagnostic challenge. To identify such factors, we analysed the Biomarkers in Younger-Onset Neurocognitive Disorders cohort, a study of individuals <65 years old presenting with neurocognitive symptoms for a diagnosis and who have undergone cognitive and biomarker analyses.

METHODS

Sixty-five participants (median age at assessment of 56 years, 45% female) were recruited during their index presentation to the Royal Melbourne Hospital Neuropsychiatry Centre, a tertiary specialist service in Melbourne, Australia, and categorized as either early-onset Alzheimer's disease (n = 18), non-Alzheimer's disease neurodegeneration (n = 23) or primary psychiatric disorders (n = 24). Levels of neurofilament light chain, glial fibrillary acidic protein and phosphorylated-tau 181, apolipoprotein E genotype and late-onset Alzheimer's disease polygenic risk scores were determined. Information-theoretic model selection identified discriminatory factors.

RESULTS

Neurofilament light chain, glial fibrillary acidic protein and phosphorylated-tau 181 levels were elevated in early-onset Alzheimer's disease compared with other diagnostic categories. A multi-omic model selection identified that a combination of cognitive and blood biomarkers, but not the polygenic risk score, discriminated between early-onset Alzheimer's disease and primary psychiatric disorders (area under the curve ⩾ 0.975, 95% confidence interval: 0.825-1.000). Phosphorylated-tau 181 alone significantly discriminated between early-onset Alzheimer's disease and non-Alzheimer's disease neurodegeneration causes (area under the curve = 0.950, 95% confidence interval: 0.877-1.00).

DISCUSSION

Discriminating between early-onset Alzheimer's disease, non-Alzheimer's disease neurodegeneration and primary psychiatric disorders causes of young-onset neurocognitive symptoms is possible by combining cognitive profiles with blood biomarkers. These results support utilizing blood biomarkers for the work-up of young-onset neurocognitive symptoms and highlight the need for the development of a young-onset Alzheimer's disease-specific polygenic risk score.

Distinct peripheral pro-inflammatory profile associated with tuberous sclerosis complex and epilepsy

OBJECTIVE

Tuberous sclerosis complex (TSC) is a monogenetic disorder associated with sustained mechanistic target of rapamycin (mTOR) activation, leading to heterogeneous clinical manifestations. Epilepsy and renal angiomyolipoma are the most important causes of morbidity in adult people with TSC (pwTSC). mTOR is a key player in inflammation, which in turn could influence TSC-related clinical manifestations. Reliable biomarkers are lacking to monitor and predict evolution and response to treatment for epilepsy in pwTSC. Inflammation has been implicated in epileptogenesis in non-TSC-related epilepsy. We aimed to characterize the relation between markers of neuroglial activation/injury, markers of peripheral inflammation, and active epilepsy in pwTSC to identify accessible biomarkers and potential new therapeutic targets.

METHODS

We performed a cross-sectional study to investigate markers of central nervous system (CNS) (neurofilament light [NfL] and glial fibrillary acidic protein [GFAP]) and peripheral (45 cytokines) inflammation in the peripheral blood of pwTSC (n = 46) vs age- and sex-matched healthy controls (HCs) (n = 26). In pwTSC, markers associated with active epilepsy (n = 23/46) were compared to non-TSC epilepsy controls (n = 18). Observations on markers of neuroglial activation/injury (GFAP, NfL) were confirmed in an independent TSC cohort (n = 45; 69% with active epilepsy).

RESULTS

We report that TSC is characterized by elevated serum levels of marker of astrogliosis (GFAP), pro-inflammatory molecules (interleukin 1β [IL-1β], CXCL8) and trophic factor (epidermal growth factor [EGF]) compared to HCs and to non-TSC-related epilepsy controls. Among pwTSC, renal angiomyolipoma presence and size was associated with IL-15. It is notable that active epilepsy in pwTSC was associated with higher levels of GFAP compared to pwTSC without epilepsy, which was confirmed in an external validation cohort, and with elevated levels of pro-inflammatory cytokines (IL-17A, IL-17C, tumor necrosis factor α [TNF-α]), not significantly related to seizure activity or treatment with mTOR inhibitor. These associations remained significant after adjusting for age and sex.

SIGNIFICANCE

These results suggest that key inflammatory mediators could contribute to epileptogenesis and represent novel biomarkers and therapeutic targets in TSC.

A French multicenter analytical evaluation of the automated Lumipulse G sNfL blood assay (Fujirebio®) and its comparison to four other immunoassays for serum neurofilament light chain assessment in clinical settings

OBJECTIVES

Measurement of serum neurofilament light chain (sNfL) protein is becoming a key biomarker for many neurological diseases. Several immunoassays have been developed to meet these clinical needs, revealing significant differences in terms of variability and results. Here, we propose a French multicenter comparison of 5 sNfL assays.

METHODS

6 replicates of 3 pools with low (10 pg/mL), medium (30 pg/mL) and high (100 pg/mL) sNfL values and one replicate of 12 samples with growing sNfL values were analyzed by six independent French clinical laboratories. The analytical performances of the sNfL blood assay (Fujirebio®) on Lumipulse G were first evaluated then compared to four other immunoassays: NF-light V2 (Quanterix®) on SiMOA HD-X, Human NF-L (Biotechne®) on Ella, R-Plex Human Neurofilament L (MSD®) on Sector 2400; manual ELISA test using Uman Diagnostic/Quanterix®.

RESULTS

Inter-center comparison of the Lumipulse blood assay revealed limited but significant differences in the mean sNfL values across low, medium, and high pools between each city (p < 0.001) and between the two different batches used. Coefficients of variation of pools ranged from 2.0 to 16.9 %. Z-score of sNfL results of the 12 samples ranged from -1.70 to +1.71. Inter-technique comparison showed a systematic difference of sNfL values, with a overestimation of MSD and Ella over other tests. Nonetheless, results were all significantly correlated (p < 0.001).

CONCLUSION

The automated Lumipulse assay produced comparable sNfL values across laboratories; but further adjustments are needed to harmonize sNfL results. Biologists and physicians should be aware of the variability in results between different immunoassay suppliers.

Neurofilament light and glial fibrillary acidic protein in mood and anxiety disorders: A systematic review and meta-analysis

Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) are biomarkers of neuronal injury measurable in cerebrospinal fluid (CSF) and blood. Despite their potential as diagnostic tests for neurodegenerative disorders, it is unclear how they behave in mood and anxiety disorders. We conducted a systematic review and meta-analysis to investigate whether NfL and GFAP concentrations were altered in adults with mood and anxiety disorders compared to healthy controls. We searched PubMed, Web of Science, PsycINFO, MEDLINE and Embase through August 20, 2024, and assessed relevant studies and their risk of bias. The primary outcome was the standardised mean difference (SMD) and 95 % confidence interval (95 % CI) of NfL and GFAP concentrations. Twenty-nine studies comprising 2,962 individuals (927majordepression,804bipolardisorder,and1,231controls). When we compared individuals with major depression and healthy controls, there was no difference in NfL nor GFAP levels. In individuals with bipolar disorder, NfL was significantly elevated compared to controls (SMD = 0.53; 95 % CI: 0.20, 0.85; p = 0.005). Only one study reported on NfL levels anxiety disorders. Our study informs clinicians about how to interpret these emerging biomarkers in determining whether a person's symptoms are caused by a neurodegenerative or mood disorder. The mild elevation of NfL in bipolar disorder may suggest underlying neuroaxonal injury, warranting further research into its clinical and prognostic significance.

Specific plasma biomarker signatures associated with patients undergoing surgery for back pain

BACKGROUND CONTEXT

Intervertebral disc degeneration (IDD) affects numerous people worldwide. The role of inflammation is increasingly recognized but remains incompletely resolved. Peripheral molecules could access neovascularized degenerated discs and contribute to the ongoing pathology.

PURPOSE

To assess a large array of plasma molecules in patients with IDD to identify biomarkers associated with specific spinal pathologies and prognostic biomarkers for the surgery outcome.

DESIGN

Prospective observational study combining clinical data and plasma measures.

PATIENT SAMPLE

Plasma samples were collected just before surgery. Extensive clinical data (age, sex, smoking status, Modic score, glomerular filtration rate, etc.) were extracted from clinical files from 83 patients with IDD undergoing spine surgery.

OUTCOME MEASURES

Recovery 2 months postsurgery as assessed by the treating neurosurgeon.

METHODS

Over 40 biological molecules were measured in patients' plasma using multiplex assays. Statistical analyses were performed to identify associations between biological and clinical characteristics (age, sex, Body Mass Index (BMI), smoking status, herniated disc, radiculopathy, myelopathy, stenosis, MODIC score, etc.) and plasma levels of biological molecules.

RESULTS

Plasma levels of Neurofilament Light chain (NfL) were significantly elevated in patients with myelopathy and spinal stenosis compared to herniated disc. Plasma levels of C- reactive protein (CRP), Neurofilament Light chain (NfL), and Serum Amyloid A (SAA) were negatively associated, while CCL22 levels were positively associated with an efficient recovery 2 months postsurgery.

CONCLUSIONS

Our results show that CRP and CCL22 plasma levels combined with the age of the IDD patient can predict the 2-month postsurgery recovery (Area Under the Curve [AUC]=0.883). Moreover, NfL could become a valuable monitoring tool for patients with spinal cord injuries.

Clinical use of biomarkers in the era of Alzheimer's disease treatments

With the advent of treatments that specifically target Alzheimer's disease brain pathology, biomarker tests will become an increasingly important part of the routine clinical evaluation of cognitive impairment and guide clinical decision making. Clinicians must ensure they are using accurate and well-validated biomarker tests and select the most appropriate testing modality for each patient based on individual and practical considerations. The interpretation of test results may be complex and depends on the pre-test probability and test-specific factors. Biomarker results must be presented and discussed with patients in a process that is sensitive to the major implications of the results and is carefully connected to diagnosis, prognosis, and management. Advances in treatments for Alzheimer's disease will likely require non-dementia specialists to use biomarkers, necessitating major educational efforts. In the new era of Alzheimer's disease treatments, biomarkers are essential tools that will be integrated into all aspects of dementia diagnosis and care.

Neurofilament light chain in serum of cancer patients with acute neurological complications

Aim: Neurofilament light chain (NfL) is a nonspecific sensitive biomarker of axonal damage.Methods: This case series identified cancer patients with neurological complications who had serum NfL measurements and paired these results to outcomes.Results: NfL serum levels were available in 15 patients with hematological malignancies or solid tumors. The neurological complications studied were immune effector cell-associated neurotoxicity syndrome, immune checkpoint inhibitor-related encephalopathy, anoxic brain injury, Guillain-Barre syndrome, hemophagocytic lymphohistiocytosis, transverse myelitis, paraneoplastic syndrome, central nervous system demyelinating disorder and chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids. All patients but one with serum NfL >900 pg/ml died during hospitalization.Conclusion: Serum NfL levels consistently corresponded to death, disease severity or recovery in this series.

Sex differences in the relationships between 24-h rest-activity patterns and plasma markers of Alzheimer's disease pathology

BACKGROUND

Although separate lines of research indicated a moderating role of sex in both sleep-wake disruption and in the interindividual vulnerability to Alzheimer's disease (AD)-related processes, the quantification of sex differences in the interplay between sleep-wake dysregulation and AD pathology remains critically overlooked. Here, we examined sex-specific associations between circadian rest-activity patterns and AD-related pathophysiological processes across the adult lifespan.

METHODS

Ninety-two cognitively unimpaired adults (mean age = 59.85 ± 13.77 years, range = 30-85, 47 females) underwent 10 days of actigraphic recordings, and blood drawing. Standard non-parametric indices of 24-h rest-activity rhythm fragmentation (intradaily variability, IV) and stability (interdaily stability, IS) were extracted from actigraphy data using the GGIR package. Plasma concentrations of neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), amyloid-β42/40 (Aβ42/40), total tau, and tau phosphorylated at threonine 181 (p-tau181) or threonine 231 (p-tau231) were measured using Single molecule array technology. Multiple linear regression models were adjusted for age, sex, education, body mass index, and actigraphic recording duration.

RESULTS

Higher IV, indicating worse 24-h rest-activity rhythm fragmentation, was associated with elevated levels of plasma NfL (t(85) = 4.26, P < 0.0001), GFAP (t(85) = 2.49, P = 0.01), and at trend level with lower Aβ42/40 ratio values (t(85) = -1.95, P = 0.054). Lower IS, reflecting less day-to-day stability in the 24-h rest-activity rhythm, was linked to elevated levels of plasma NfL (t(85) = -2.24, P = 0.03), but not with the other plasma biomarkers. Importantly, interaction models demonstrated that male participants were driving the observed relationships between IV and plasma NfL (t(84) = 4.05, P < 0.001) or GFAP (t(84) = 3.60, P < 0.001), but also revealed a male vulnerability in models testing interactions with p-tau181 (IV: t(76) = 3.71, P < 0.001; IS: t(76) = -3.30, P = 0.001) and p-tau231 (IV: t(82) = 3.28, P = 0.002). Sensitivity analyses further showed that accounting for potential confounding factors such as APOE genotype, depression, and self-reported symptoms of possible sleep apnea did not modify the observed relationships.

CONCLUSIONS

These findings suggest that the association between disrupted circadian rest-activity patterns and AD pathophysiological processes may be more evident in cognitively unimpaired males. Our results contribute to the precision medicine approach, and they have clinical implications for improved early detection and selection of at-risk individuals to be enrolled in preventive interventions.

Cumulative Socioeconomic Status Risk is Associated With Greater Increase in Serum Neurofilament Light Chain Levels Among Middle-Aged Black Adults

BACKGROUND

This study examined the longitudinal relationship between cumulative socioeconomic status (SES) risk and serum neurofilament light chain (NfL) levels to better understand the association between social factors and a biomarker of neurodegeneration.

METHODS

We used data from the Family and Community Health Study, collecting psychosocial and blood data at 2 waves (2008) and (2019) from 254 Black Americans (43 males and 211 females). Blood samples were analyzed at each wave for serum NfL concentrations. Regression analysis and mixed-effect modeling examined relationships between cumulative SES risk and serum NfL, controlling for covariates and assessing time effects.

RESULTS

Utilizing 11-year longitudinal data, serum NfL levels increased with age. Higher cumulative SES risk at baseline correlated with elevated serum NfL at the 11-year follow-up and predicted a greater increase in NfL levels. Clinically, NfL is a sensitive biomarker for axonal injury and neurodegeneration, commonly used to detect early and preclinical stages of conditions such as Alzheimer's disease, multiple sclerosis, and other neurodegenerative disorders.

CONCLUSIONS

Our results suggest that exposure to cumulative SES risk among Black adults may contribute to elevated levels of NfL, indicating potential early neurodegeneration. Given the established role of NfL in detecting neurodegenerative processes, these findings underscore the importance of interventions that bolster social safety nets and social connectedness to enhance brain health and mitigate neurodegenerative risks.

Molecular mechanisms of neurofilament alterations and its application in assessing neurodegenerative disorders

Neurofilaments are intermediate filaments present in neurons. These provide structural support and maintain the size and shape of the neurons. Dysregulation, mutation, and aggregation of neurofilaments raise the levels of these proteins in the blood and cerebrospinal fluid (CSF), which are characteristic features of axonal damage and certain rare neurological diseases, such as Giant Axonal Neuropathy and Charcot-Mare-Tooth disease. Understanding the structure, dynamics, and function of neurofilaments has been greatly enhanced by a diverse range of biochemical and preclinical investigations conducted over more than four decades. Recently, there has been a resurgence of interest in post-translational modifications of neurofilaments, such as phosphorylation, aggregation, mutation, oxidation, etc. Over the past twenty years, several rare disorders have been studied from structural alterations of neurofilaments. These disorders are monitored by fluid biomarkers such as neurofilament light chains. Currently, there are many tools, such as Enzyme-Linked Immunosorbent Assay, Electrochemiluminescence Assay, Single-Molecule Array, Western/immunoblotting, etc., in use to assess the neurofilament proteins in Blood and CSF. However, all these techniques utilize expensive, non-specific, or antibody-based methods, which make them unsuitable for routine screening of neurodegenerative disorders. This provides room to search for newer sensitive, cost-effective, point-of-care tools for rapid screening of the disease. For a long time, the molecular mechanisms of neurofilaments have been poorly understood due to insufficient research attempts, and a deeper understanding of them remains elusive. Therefore, this review aims to highlight the available literature on molecular mechanisms of neurofilaments and the function of neurofilaments in axonal transport, axonal conduction, axonal growth, and neurofilament aggregation, respectively. Further, this review discusses the role of neurofilaments as potential biomarkers for the identification of several neurodegenerative diseases in clinical laboratory practice.

Comparative neurofilament light chain trajectories in CSF and plasma in autosomal dominant Alzheimer's disease

Disease-modifying therapies for Alzheimer's disease (AD) are likely to be most beneficial when initiated in the presymptomatic phase. To track the benefit of such interventions, fluid biomarkers are of great importance, with neurofilament light chain protein (NfL) showing promise for monitoring neurodegeneration and predicting cognitive outcomes. Here, we update and complement previous findings from the Dominantly Inherited Alzheimer Network Observational Study by using matched cross-sectional and longitudinal cerebrospinal fluid (CSF) and plasma samples from 567 individuals, allowing timely comparative analyses of CSF and blood trajectories across the entire disease spectrum. CSF and plasma trajectories were similar at presymptomatic stages, discriminating mutation carriers from non-carrier controls 10-20 years before the estimated onset of clinical symptoms, depending on the statistical model used. However, after symptom onset the rate of change in CSF NfL continued to increase steadily, whereas the rate of change in plasma NfL leveled off. Both plasma and CSF NfL changes were associated with grey-matter atrophy, but not with Aβ-PET changes, supporting a temporal decoupling of Aβ deposition and neurodegeneration. These observations support NfL in both CSF and blood as an early marker of neurodegeneration but suggest that NfL measured in the CSF may be better suited for monitoring clinical trial outcomes in symptomatic AD patients.

The Impact of Cognitive Behavioral Therapy for Insomnia on Neurofilament Light and Phosphorylated Tau in Individuals with a Concussion

BACKGROUND

Concussions damage neurologic tissue, increasing release of intercellular proteins including phosphorylated Tau (pTau) and neurofilament light (NfL). Disrupted sleep from a concussion negatively impacts the ability of the glymphatic system to remove cellular waste from the brain.

OBJECTIVE

The purpose of this study was to determine if enhancing sleep using Cognitive Behavioral Therapy for Insomnia (CBT-I) impacts pTau and NFL levels following a concussion.

METHODS

This is pre/post intervention analysis of a larger wait-list control study. Participants had their blood sampled pre/post the CBT-I intervention which was analyzed using SIMOA analytics. Paired sampling statistics and linear regression models were used to examine how insomnia severity impacts pTau181 and NfL.

RESULTS

Twenty-eight participants were enrolled in this study. Age and baseline protein level were significantly associated with post-intervention protein levels, but post-intervention insomnia severity was not associated with post-intervention protein levels. About 50% of participants that had clinically meaningful change in insomnia and had a reduction in their NfL and pTau181 values.

CONCLUSIONS

Post-intervention insomnia was not associated with post-intervention NfL or pTau. Yet, on an individual level, ~50% of participants had a clinically meaningful change in insomnia and reduced level of NfL and pTau 18.1.

CLINICAL TRIAL REGISTRATION

NCT04885205 https://clinicaltrials.gov.

Serum and CSF biomarkers in asymptomatic patients during primary HIV infection: a randomized study

It is debated whether CNS involvement begins during acute human immunodeficiency virus (HIV) infection in persons without meningitis/encephalitis and whether specific antiretroviral drugs or combinations would be beneficial. Neurologically asymptomatic participants enrolled in a randomized and controlled study comparing three combination antiretroviral regimens (tenofovir alafenamide/emtricitabine plus dolutegravir; darunavir; or both) during primary HIV infection were enrolled. Serum and CSF were collected at baseline and at 12 and 48 (serum only) weeks after treatment initiation. Single molecule array was used to measure neurofilament light chain (NFL), total tau protein (Tau), brain-derived neurotrophic factor, glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase. We assessed the longitudinal change in biomarkers over time, in addition to the change in the prevalence of serum NFL concentrations above previously published age-adjusted cut-offs (7 pg/ml if 5-18 years, 10 pg/ml if 18-51 years, 15 pg/ml if 51-61 years, 20 pg/ml if 61-70 years and 35 pg/ml if >70 years). Serum was available from 47 participants at all time points, and CSF was available from 13 participants at baseline and 7 at Week 12. We observed a significant direct serum-to-CSF correlation for NFL (ρ = 0.692, P = 0.009), GFAP (ρ = 0.659, P = 0.014) and brain-derived neurotrophic factor (ρ = 0.587, P = 0.045). Serum (ρ = 0.560, P = 0.046) and CSF NFL (ρ = 0.582, P = 0.037) concentrations were directly associated with CSF HIV RNA levels. We observed a significant decrease over time in serum NFL (P = 0.006) and GFAP (P = 0.006) but not in the other biomarkers. No significant difference was observed among the treatment arms. At baseline, serum and CSF age-adjusted NFL levels were above age-adjusted cut-offs in 23 (48.9%) and four participants (30.8%), respectively; considering serum NFL, this proportion was lower at Weeks 12 (31.9%, P = 0.057) and 48 (27.7%, P = 0.13). A relevant proportion of neurologically asymptomatic participants had abnormal CSF and serum NFL levels during primary HIV infection. NFL and GFAP decreased in serum following combination antiretroviral therapy without significant differences among the treatment arms.

Plasma and CSF neurofilament light chain distinguish neurodegenerative from primary psychiatric conditions in a clinical setting

INTRODUCTION

People with neurodegenerative disorders (ND) frequently face diagnostic delay and misdiagnosis. We investigated blood and cerebrospinal fluid (CSF) neurofilament light chain (NfL) to distinguish ND from primary psychiatric disorders (PPD), a common challenge in clinical settings.

METHODS

Plasma and CSF NfL levels were measured and compared between groups, adjusting for age, sex, and weight.

RESULTS

A total of 337 participants were included: 136 ND, 77 PPD, and 124 Controls. Plasma NfL was 2.5-fold elevated in ND compared to PPD and had strong diagnostic performance (area under the curve, [AUC]: 0.86, 81%/85% specificity/sensitivity) that was comparable to CSF NfL (2-fold elevated, AUC: 0.89, 95%/71% specificity/sensitivity). Diagnostic performance was especially strong in younger people (40- < 60 years). Additional findings were cutoffs optimized for sensitivity and specificity, and issues important for future clinical translation.

CONCLUSIONS

This study adds important evidence for a simple blood-based biomarker to assist as a screening test for neurodegeneration and distinction from PPD, in clinical settings.

HIGHLIGHTS

NfL levels were significantly higher in ND versus PPD. Plasma NfL showed strong diagnostic performance, comparable to CSF NfL, to distinguish ND from PPD. Diagnostic performance was higher in younger people, where diagnostic challenges are greater. Further research is needed on analytical and reference range factors, for clinical translation. These findings support a simple screening blood test for neurodegeneration.

Investigation of serum neurofilament light chain as a biomarker in Fabry disease

Fabry disease (FD) constitutes a rare, X-linked lysosomal storage disorder affecting multiple organ systems, most notably heart, kidneys, and the central nervous system. Neurofilament light chains (NfL) have emerged as a prime candidate for a body fluid biomarker reflecting neuro-axonal injury. We aimed to evaluate its addition to the diagnostic and monitoring armamentarium in FD. Serum NfL concentrations (sNfL) were measured in 50 people with FD (PwFD) and 30 healthy control subjects (HC) using the Simoa© technology, followed by calculation of Z-scores adjusted for age and body mass index. In addition, clinical disease severity in PwFD was measured using the FOS-MSSI (Fabry outcome study - Mainz severity score index), which comprises clinical and paraclinical parameters. PwFD show elevated sNfL Z-scores compared to HC (PwFD: 1.12 [SD 1.5], HC: 0.01 [SD 1.2], p < 0.001). In PwFD, males showed higher sNfL Z-scores than females (1.75 [SD 1.5] vs. 0.73 [SD 1.4]). Importantly, sNfL Z-scores were increased in PwFD with ischemic white matter lesions of the CNS (1.5, SD 2.2 vs. 0.5, SD 2.9, p = 0.03). In our small cohort, sNfL Z-scores correlated fairly with FOS-MSSI (Kendall's-Tau [τ] = 0.25, p = 0.01), and, interestingly with serum creatinine (τ = 0.28, p = 0.005) and estimated glomerular filtration rate (eGFR, τ =-0.28, p = 0.005). Based on these exploratory results, sNfL might provide value as a biomarker of neuroaxonal damage in FD, possibly reflecting cerebrovascular injury. Additionally, the correlation of sNfL with renal function warrants further investigation.

Plasma Biomarkers of Traumatic Brain Injury in Adolescents With Sport-Related Concussion

Importance

Blood-based biomarkers may clarify underlying neuropathology and potentially assist in clinical management of adolescents with sport-related concussion (SRC).

Objective

To investigate the association between SRC and plasma biomarkers in adolescents.

Design, Setting, and Participants

Prospective cohort study in Canadian sport and clinic settings (Surveillance in High Schools and Community Sport to Reduce Concussions and Their Consequences study; September 2019 to November 2022). Participants were a convenience sample of 849 adolescent (ages 10-18 years) sport participants with blood samples. Data were analyzed from February to September 2023.

Exposures

Blood collection and clinical testing preseason (uninjured) and post-SRC follow-ups (ie, ≤72 hours, 1 week, and biweekly until medical clearance to return to play [RTP]).

Main Outcomes and Measures

Plasma glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase-L1 (UCH-L1), neurofilament light (NfL), and total tau (t-tau) were assayed. Group-level comparisons of biomarker levels were conducted between uninjured and post-SRC intervals (postinjury day [PID] 0-3, 4-10, 11-28, and >28) considering age and sex as modifiers. Secondary analyses explored associations between biomarker concentrations and clinical outcomes (Sport Concussion Assessment Tool, Fifth Edition [SCAT5] symptom scores and time to RTP).

Results

This study included 1023 plasma specimens from 695 uninjured participants (467 male participants [67.2%]; median [IQR] age, 15.90 [15.13-16.84] years) and 154 participants with concussion (78 male participants [51.0%]; median [IQR] age, 16.12 [15.31-17.11] years). Acute (PID 0-3) differences relative to uninjured levels were found for GFAP (female participants: 17.8% increase; β = 0.164; 95% CI, 0.064 to 0.263; P = .001; male participants: 17.1% increase; β = 0.157; 95% CI, 0.086 to 0.229; P < .001), UCH-L1 (female participants: 43.4% increase; β = 0.361; 95% CI, 0.125 to 0.596; P = .003), NfL (male participants: 19.0% increase; β = 0.174; 95% CI, 0.087 to 0.261; P < .001), and t-tau (female participants: -22.9%; β = -0.260; 95% CI, -0.391 to -0.130; P < .001; male participants: -18.4%; β = -0.203; 95% CI, -0.300 to -0.106; P < .001). Differences were observed for all biomarkers at PID 4 to 10, 11 to 28, and greater than 28 compared with uninjured groups. GFAP, NfL, and t-tau were associated with SCAT5 symptom scores across several PID intervals. Higher GFAP after 28 days post-SRC was associated with earlier clearance to RTP (hazard ratio, 4.78; 95% CI, 1.59 to 14.31; P = .01). Male participants exhibited lower GFAP (-9.7%), but higher UCH-L1 (21.3%) compared with female participants. Age was associated with lower GFAP (-5.4% per year) and t-tau (-5.3% per year).

Conclusions and Relevance

In this cohort study of 849 adolescents, plasma biomarkers differed between uninjured participants and those with concussions, supporting their continued use to understand concussion neuropathology. Age and sex are critical considerations as these biomarkers progress toward clinical validation.

Plasma neurofilament light chain levels in chemotherapy-induced peripheral neurotoxicity according to type of anticancer drug

BACKGROUND AND PURPOSE

A real-time biomarker in chemotherapy-induced peripheral neurotoxicity (CIPN) would be useful for clinical decision-making during treatment. Neurofilament light chain (NfL) can be detected in blood in the case of neuroaxonal damage. The aim of the study was to compare the levels of plasma NfL (pNfL) according to the type of chemotherapeutic agent and the severity of CIPN.

METHODS

This single-center prospective observational longitudinal study included patients treated with paclitaxel (TX; n = 34), brentuximab vedotin (BV; n = 29), or oxaliplatin (PT; n = 19). All patients were assessed using the Total Neuropathy Score-clinical version and Common Terminology Criteria for Adverse Events before, during, and up to 6-12 months after the end of treatment. Nerve conduction studies (NCS) were performed before and after chemotherapy discontinuation. Consecutive plasma samples were analyzed for NfL levels using a Simoa® analyzer. Changes in pNfL were compared between groups and were eventually correlated with clinical and NCS data. Clinically relevant (CR) CIPN was considered to be grade ≥ 2.

RESULTS

Eighty-two patients, mostly women (59.8%), were included. One third of the patients who received TX (29.4%), BV (31%), or PT (36.8%) developed CR-CIPN, respectively, without differences among them (p = 0.854). Although pNfL significantly increased during treatment and decreased throughout the recovery period in all three groups, patients receiving TX showed significantly greater and earlier changes in pNfL levels compared to the other agents (p < 0.001).

CONCLUSIONS

A variable change in pNfL is observed depending on the type of agent and mechanism of neurotoxicity with comparable CIPN severity, strongly implying the need to identify different cutoff values for each agent.

Age-adjusted CSF t-tau and NfL do not improve diagnostic accuracy for prodromal Alzheimer's disease

Cerebrospinal fluid total-tau (t-tau) and neurofilament light chain (NfL) are biomarkers of neurodegeneration and are increased in Alzheimer's disease (AD). In order to adjust for age-related increases in t-tau and NfL, cross-sectional age-adjusted norms were developed based on amyloid negative cognitively normal (CN) adults aged 41-78 years (CN, n = 137). The age-adjusted norms for t-tau and NfL did not improve receiver operating curve based diagnostic accuracies in individuals with mild cognitive impairment (MCI) due to AD (AD-MCI, n = 144). Furthermore, while NfL was correlated with higher age in AD-MCI, no significant correlation was found for t-tau. The cox proportional hazard models, applied in 429 participants with baseline t-tau and NfL, showed higher hazard ratio of progression to MCI or dementia without age-adjustments (HR = 3.39 for t-tau and HR = 3.17 for NfL), as compared to using our norms (HR = 2.29 for t-tau and HR = 1.89 for NfL). Our results indicate that utilizing normative reference data could obscure significant age-related increases in these markers associated with neurodegeneration and AD leading to a potential loss of overall diagnostic accuracy.

Plasma concentrations of glial fibrillary acidic protein, neurofilament light, and tau in Alexander disease

INTRODUCTION

Alexander disease (AxD) is a rare leukodystrophy caused by dominant gain-of-function mutations in the gene encoding the astrocyte intermediate filament, glial fibrillary acidic protein (GFAP). However, there is an urgent need for biomarkers to assist in monitoring not only the progression of disease but also the response to treatment. GFAP is the obvious candidate for such a biomarker, as it is measurable in body fluids that are readily accessible for biopsy, namely cerebrospinal fluid and blood. However, in the case of ASOs, the treatment that is furthest in development, GFAP is the target of therapy and presumably would go down independent of disease status. Hence, there is a critical need for biomarkers that are not directly affected by the treatment strategy.

METHODS

We explored the potential utility of biomarkers currently being studied in other neurodegenerative diseases and injuries, specifically neurofilament light protein (NfL), phosphorylated forms of tau, and amyloid-β peptides (Aβ42/40).

RESULTS AND CONCLUSIONS

Here, we report that GFAP is elevated in plasma of all age groups afflicted by AxD, including those with adult onset. NfL and p-tau are also elevated, but to a much lesser extent than GFAP. In contrast, the levels of Aß40 and Aß42 are not altered in AxD.

Elevated plasma neurofilament light and glial fibrillary acidic protein in epilepsy versus nonepileptic seizures and nonepileptic disorders

OBJECTIVE

Research suggests that recurrent seizures may lead to neuronal injury. Neurofilament light chain protein (NfL) and glial fibrillary acidic protein (GFAP) levels increase in cerebrospinal fluid and blood in response to neuroaxonal damage, and they have been hypothesized as potential biomarkers for epilepsy. We examined plasma NfL and GFAP levels and their diagnostic utility in differentiating patients with epilepsy from those with psychogenic nonepileptic seizures (PNES) and other nonepileptic disorders.

METHODS

We recruited consecutive adults admitted for video-electroencephalographic monitoring and formal neuropsychiatric assessment. NfL and GFAP levels were quantified and compared between different patient groups and an age-matched reference cohort (n = 1926) and correlated with clinical variables in patients with epilepsy.

RESULTS

A total of 138 patients were included, of whom 104 were diagnosed with epilepsy, 22 with PNES, and 12 with other conditions. Plasma NfL and GFAP levels were elevated in patients with epilepsy compared to PNES, adjusted for age and sex (NfL p = .04, GFAP p = .04). A high proportion of patients with epilepsy (20%) had NfL levels above the 95th age-matched percentile compared to the reference cohort (5%). NfL levels above the 95th percentile of the reference cohort had a 95% positive predictive value for epilepsy. Patients with epilepsy who had NfL levels above the 95th percentile were younger than those with lower levels (37.5 vs. 43.8 years, p = .03).

SIGNIFICANCE

An elevated NfL or GFAP level in an individual patient may support an underlying epilepsy diagnosis, particularly in younger adults, and cautions against a diagnosis of PNES alone. Further examination of the association between NfL and GFAP levels and specific epilepsy subtypes or seizure characteristics may provide valuable insights into disease heterogeneity and contribute to the refinement of diagnosis, understanding pathophysiological mechanisms, and formulating treatment approaches.

Plasma neurofilament light protein is differentially associated with age in individuals with treatment-resistant schizophrenia and bipolar affective disorder compared to controls

Accelerated brain ageing has been observed in multiple psychiatric disorders. This study examined whether relationships between age and plasma neurofilament light (NfL) protein differed in individuals with psychiatric disorders (major depressive disorder (n = 42), bipolar affective disorder (n = 121), treatment-resistant schizophrenia (TRS, n = 82)) compared to two healthy control (HC) groups (n = 1,926 and n = 59). Compared to two independent HC samples, individuals with TRS demonstrated a stronger positive relationship between age and NfL levels. Individuals with BPAD had a stronger negative relationship between age and NfL levels compared to the large normative HC cohort, but not locally-acquired HCs. These findings show that plasma NfL levels are differentially associated with age in individuals with TRS and BPAD compared to healthy individuals.

Alzheimer disease-related biomarkers and cancer-related cognitive decline: the Thinking and Living with Cancer study

PURPOSE

We evaluated whether plasma Alzheimer disease (AD)-related biomarkers were associated with cancer-related cognitive decline among older breast cancer survivors.

METHODS

We included survivors aged 60-90 years with primary stage 0-III breast cancers (n = 236) and frequency-matched noncancer control paricipant (n = 154) who passed a cognitive screen and had banked plasma specimens. Participants were assessed at baseline (presystemic therapy) and annually for up to 60 months. Cognition was measured using tests of attention, processing speed, and executive function and learning and memory; perceived cognition was measured by the Functional Assessment of Cancer Therapy-Cognitive Function v3 Perceived Cognitive Impairments. Baseline plasma neurofilament light, glial fibrillary acidic protein, β-amyloid 42 and 40 and phosphorylated tau 181 were assayed using single molecule arrays. Mixed models tested associations between cognition and baseline AD biomarkers, time, group (survivor vs control participant), and their 2- and 3-way interactions, controlling for age, race, Wide Range 4 Achievement Test Word Reading score, comorbidity, and body mass index; 2-sided P values of .05 were considered statistically significant.

RESULTS

There were no group differences in baseline AD-related biomarkers except survivors had higher baseline neurofilament light levels than control participants (P = .013). Survivors had lower adjusted longitudinal attention, processing speed, and executive function than control participants starting from baseline and continuing over time (P ≤ .002). However, baseline AD-related biomarker levels were not independently associated with adjusted cognition over time, except control participants had lower attention, processing speed, and executive function scores with higher glial fibrillary acidic protein levels (P = .008).

CONCLUSION

The results do not support a relationship between baseline AD-related biomarkers and cancer-related cognitive decline. Further investigation is warranted to confirm the findings, test effects of longitudinal changes in AD-related biomarkers, and examine other mechanisms and factors affecting cognition presystemic therapy.

Fluid biomarkers in multiple sclerosis: from current to future applications

Multiple sclerosis (MS) is an immune-mediated inflammatory and degenerative disorder of the central nervous system (CNS) with heterogeneous clinical manifestations. In the last decade, the landscape of cerebrospinal fluid (CSF) and blood biomarkers as potential key tools for MS diagnosis, prognosis and treatment monitoring has evolved considerably, alongside magnetic resonance imaging (MRI). CSF analysis has the potential not only to provide information on the underlying immunopathology of the disease and exclude differential diagnoses, but also to predict the risk of future relapses and disability accrual, guide therapeutic decisions and thus improve patient outcomes. This Series article overviews the biological framework and current applicability of fluid biomarkers for MS, exploring their potential role in the molecular characterisation of the disease. We discuss recent advances in the field of neurochemistry that enabled the detection of brain-derived proteins in blood, opening the door to much more efficient longitudinal disease monitoring. Furthermore, we identify the current challenges in the application of fluid biomarkers for MS in a real-world setting, while offering recommendations for harnessing their full potential as key paraclinical tools to improve patient management and personalise treatment.

Clinical utility of the Lumipulse™ immunoassay for plasma neurofilament light chain in multiple sclerosis

OBJECTIVE

Blood neurofilament light chain (NfL) is robustly associated with disease worsening in multiple sclerosis (MS), though potentially affected by concomitant factors also determining neuro-axonal loss. We investigated the association between plasma NfL (pNfL) measured with Lumipulse™ immunoassay and demographic and clinical variables in MS.

METHODS

This cross-sectional study included 685 people with MS (age 49.7 ± 12.4 years; sex 65.55% females). On the same day, we collected plasma samples, along with demographics, comorbidities, and clinical variables (MS disease duration, expanded disability status scale (EDSS), Symbol Digit Modalities Test (SDMT), descriptor of disease progression, current disease modifying treatment (DMT), number of previous DMTs, evidence of disease activity in the past year (i.e. relapse or MRI new lesions), EDSS progression). pNfL was evaluated using Lumipulse™ fully automated chemiluminescent enzyme immunoassay.

RESULTS

On multivariable linear regression model, higher pNfL was associated with higher EDSS (Coeff = 1.73; 95%CI 0.78, 2.68; p < 0.01), recent disease activity (Coeff = 15.70; 95%CI = 5.35, 26.06; p < 0.01), and presence of cardiovascular comorbidity (Coeff = 3.84; 95%CI 0.48, 7.20; p = 0.025). Lower pNfL was found in patients on DMT treatment (Coeff = -10.23; 95%CI -18.42, -2.04; p = 0.015), when compared with no DMT (reference). For 77.81% of our population there was correspondence between pNfL levels and two previously-validated cutoffs.

CONCLUSIONS

pNfL measured using Lumipulse™ confirms known associations with MS activity, disability and treatments, and related confounding (e.g., cardiovascular comorbidity), thus granting further utilization in research and clinical practice.

High levels of plasma neurofilament light chain correlated with brainstem and peripheral nerve damage

BACKGROUND AND OBJECTIVES

Blood neurofilament light chain (NfL) is a minimally invasive, but highly sensitive biomarker of neurological diseases. However, diseases and neurological damage associated with increased NfL remain unclear. Therefore, the present study investigated factors associated with increased plasma NfL levels in various neurological diseases, focal lesions and pathological processes.

METHODS

This was a retrospective cohort study on 410 participants with various neurological diseases and 17 healthy and cognitively unimpaired controls (HCU). Plasma samples were analyzed to measure NfL using ECL immunoassay. The focal lesions were classified as the cerebrum, cerebellum, brainstem, meninges, spinal cord, peripheral nerves, neuromuscular junction, and muscles based on medical records. A multiple regression analysis and receiver operating characteristic curve (ROC) analysis were performed to investigate whether plasma NfL levels predict specific diseases and focal lesions.

RESULTS

Plasma NfL levels discriminated between the HCU and all disease groups (area under the curve (AUC), 0.97), with a cut-off value of 63.4 pg/mL. A multiple regression analysis of focal lesions adjusted by pathogenic processes showed that brainstem and peripheral nerve involvement was associated with higher plasma NfL levels. A cut-off value of 53.8 pg/mL of NfL discriminated between the HCU and neurological disease group except for brainstem or peripheral disorders (AUC 0.962), while a cut-off value of 208.0 pg/mL distinguished this group from brainstem or peripheral nervous system disorders (AUC 0.716).

DISCUSSION

These results demonstrate that plasma NfL has a potential to be a highly sensitive biomarker for neurological diseases and focal lesions.

Clinical Accuracy of Serum Neurofilament Light to Differentiate Frontotemporal Dementia from Primary Psychiatric Disorders is Age-Dependent

BACKGROUND

Symptoms of behavioral variant frontotemporal dementia (bvFTD) overlap with primary psychiatric disorders (PPD) making diagnosis challenging. Serum neurofilament light (sNfL) is a candidate biomarker to distinguish bvFTD from PPD, but large-scale studies in PPD are lacking.

OBJECTIVE

Determine factors that influence sNfL from a large database of PPD patients, and test its diagnostic accuracy.

DESIGN, SETTINGS, SUBJECTS, MEASUREMENTS

Clinical data of people aged 40-81 were obtained from healthy subjects (n = 69), and patients with PPD (n = 848) or bvFTD (n = 82). sNfL was measured using Simoa technology on an HD-X instrument. Data were analyzed using general linear models, and Receiver Operating Characteristic (ROC) curve analyses to determine global and age-specific sNfL cutoffs to distinguish bvFTD from PPD, using the Youden Index.

RESULTS

sNfL increased with age, while sex, BMI and diabetes status were modestly associated with sNfL. sNfL was slightly higher in PPD than healthy subjects (14.1 versus 11.7 pg/mL), when controlling for covariates. sNfL was markedly lower in PPD than bvFTD (14.1 versus 44.1 pg/mL). sNfL could differentiate PPD from bvFTD with an AUC = 0.868, but the effect was driven by the younger subjects between age 40-60 years at a cutoff of 16.0 pg/mL. No valid cutoff was detected over age 60, however, values of sNfL above 38.5 pg/mL, or below 13.9 pg/mL, provided 90% diagnostic certainty of bvFTD or PPD, respectively.

CONCLUSION

PPD have mildly elevated sNfL compared to healthy subjects but much lower than bvFTD. Results support the use of sNfL as a biomarker to differentiate PPD from bvFTD at age 60 or below, but accuracy decreases in older ages.

Introducing neurofilament light chain measure in psychiatry: current evidence, opportunities, and pitfalls

The recent introduction of new-generation immunoassay methods allows the reliable quantification of structural brain markers in peripheral matrices. Neurofilament light chain (NfL), a neuron-specific cytoskeletal component released in extracellular matrices after neuroaxonal impairment, is considered a promising blood marker of active brain pathology. Given its sensitivity to a wide range of neuropathological alterations, NfL has been suggested for the use in clinical practice as a highly sensitive, but unspecific tool to quantify active brain pathology. While large efforts have been put in characterizing its clinical profile in many neurological conditions, NfL has received far less attention as a potential biomarker in major psychiatric disorders. Therefore, we briefly introduce NfL as a marker of neuroaxonal injury, systematically review recent findings on cerebrospinal fluid and blood NfL levels in patients with primary psychiatric conditions and highlight the opportunities and pitfalls. Current evidence suggests an elevation of blood NfL levels in patients with major depression, bipolar disorder, psychotic disorders, anorexia nervosa, and substance use disorders compared to physiological states. However, blood NfL levels strongly vary across diagnostic entities, clinical stage, and patient subgroups, and are influenced by several demographic, clinical, and analytical factors, which require accurate characterization. Potential clinical applications of NfL measure in psychiatry are seen in diagnostic and prognostic algorithms, to exclude neurodegenerative disease, in the assessment of brain toxicity for different pharmacological compounds, and in the longitudinal monitoring of treatment response. The high inter-individual variability of NfL levels and the lack of neurobiological understanding of its release are some of the main current limitations. Overall, this primer aims to introduce researchers and clinicians to NfL measure in the psychiatric field and to provide a conceptual framework for future research directions.

Head-to-head comparison of four plasma neurofilament light chain (NfL) immunoassays

BACKGROUND

Neurofilament Light Chain (NfL) is an emerging blood biomarker of neuro-axonal injury and neurodegeneration with the potential to be used in the clinical management of various neurological conditions. Various NfL immunoassays are in development on high-throughput automated systems, but little information is available related to the comparability between assays. In this study, we performed a head-to-head comparison of four NfL immunoassays using plasma samples from individuals with various neurological conditions.

METHODS

EDTA plasma samples in which NfL was ordered clinically were stratified according to diagnosis. NfL concentrations (pg/mL) in plasma were obtained using the Quanterix Simoa®, the Roche Elecsys, the Siemens Healthineers Atellica®IM, and the Fujirebio Lumipulse® NfL assays. Passing-Bablok regression analyses were performed to assess the correlation and bias between methods. Additionally, the distribution of NfL concentrations for each assay was assessed in three disease groups: amyotrophic lateral sclerosis (ALS) upon initial diagnosis, ALS treated, and multiple sclerosis (MS).

RESULTS

The R2 between assays were all ≥ 0.95, however, significant proportional bias was observed between some assays. In particular, the Roche Elecsys assay NfL concentrations were significantly lower (∼85 %) when compared against the other three assays. The four assays were comparable with regards to the percentage of patients that were identified as having an elevated NfL result in the various clinical groups: ALS initial diagnoses (83-94 %), ALS untreated (93-100 %), and MS (8-18 %).

CONCLUSIONS

This is the first study describing a head-to-head comparison of four automated NfL immunoassays. We demonstrate that there is a strong correlation between assays but a lack of standardization which is evident by the bias observed between some of the evaluated methods. These analytical differences will be important to consider when using NfL as a biomarker of neurodegeneration.

Mapping neurodegeneration across the Huntington's disease spectrum: a five-year longitudinal analysis of plasma neurofilament light

BACKGROUND

Neurofilament light (NfL) has previously been highlighted as a potential biomarker for Huntington's Disease (HD) using cross-sectional analyses. Our study aim was to investigate how longitudinal trajectories of plasma NfL relate to HD disease stage.

METHODS

108 participants [78 individuals with the HD mutation, and 30 healthy controls (HC)] were included in this study. Individuals with the HD mutation were categorised separately by both HD-Integrated Staging System (HD-ISS) (Study 1) and PIN score-Approximated Staging System (PASS) (Study 2) criteria. Plasma NfL trajectories were examined using Mixed Linear Modeling (MLM); associations with symptom presentation were assessed using Spearman's rho correlations.

FINDINGS

The MLM coefficients for disease stage (HD-ISS β = 32.73, p < 0.0001; PASS β = 33.00, p < 0.0001) and disease stage∗time (HD-ISS β = 7.85, p = 0.004; PASS β = 6.58, p = 0.0047) suggest these are significant contributors to plasma NfL levels. In addition, the plasma NfL rate of change varied significantly across time (HD-ISS β = 3.14, p = 0.04; PASS β = 2.94, p = 0.050). The annualised rate of change was 8.32% for HC; 10.55%, 12.75% and 15.62% for HD-ISS Stage ≤1, Stage 2, and Stage 3, respectively; and 12.13%, 10.46%, 10.33%, 17.52%, for PASS Stage 0, Stage 1, Stage 2, and Stage 3, respectively. Plasma NfL levels correlated with the Symbol Digit Modalities Test (SDMT) in HD-ISS Stage ≤1, and both SDMT and Total Motor Score in Stage 3 (ps < 0.01).

INTERPRETATION

Our findings suggest that plasma NfL levels increase linearly across earlier disease stages, correlating with the cognitive SDMT measure. Thereafter, an increase or surge in plasma NfL levels, paired with correlations with both cognitive and motor measures, suggest a late acceleration in clinical and pathological progression.

FUNDING

NIH (NS111655); the UCSD HDSA CoE; the UCSD ADRC (NIH-NIA P30 AG062429).

Serum Markers of Neurodegeneration Are Strongly Linked to Heart Failure Severity and Outcome

BACKGROUND

Cognitive impairment is prevalent in patients with heart failure with reduced ejection fraction (HFrEF), affecting self-care and outcomes. Novel blood-based biomarkers have emerged as potential diagnostic tools for neurodegeneration.

OBJECTIVES

This study aimed to assess neurodegeneration in HFrEF by measuring neurofilament light chain (NfL), total tau (t-tau), amyloid beta 40 (Aβ40), and amyloid beta 42 (Aβ42) in a large, well-characterized cohort.

METHODS

The study included 470 patients with HFrEF from a biobank-linked prospective registry at the Medical University of Vienna. High-sensitivity single-molecule assays were used for measurement. Unplanned heart failure (HF) hospitalization and all-cause death were recorded as outcome parameters.

RESULTS

All markers, but not the Aβ42:Aβ40 ratio, correlated with HF severity, ie, N-terminal pro-B-type natriuretic peptide and NYHA functional class, and comorbidity burden and were significantly associated with all-cause death and HF hospitalization (crude HR: all-cause death: NfL: 4.44 [95% CI: 3.02-6.53], t-tau: 5.04 [95% CI: 2.97-8.58], Aβ40: 3.90 [95% CI: 2.27-6.72], and Aβ42: 5.14 [95% CI: 2.84-9.32]; HF hospitalization: NfL: 2.48 [95% CI: 1.60-3.85], t-tau: 3.44 [95% CI: 1.95-6.04], Aβ40: 3.13 [95% CI: 1.84-5.34], and Aβ42: 3.48 [95% CI: 1.93-6.27]; P < 0.001 for all). These associations remained statistically significant after multivariate adjustment including N-terminal pro-B-type natriuretic peptide. The discriminatory accuracy of NfL in predicting all-cause mortality was comparable to the well-established risk marker N-terminal pro-B-type natriuretic peptide (C-index: 0.70 vs 0.72; P = 0.225), whereas the C-indices of t-tau, Aβ40, Aβ42, and the Aβ42:Aβ40 ratio were significantly lower (P < 0.05 for all).

CONCLUSIONS

Neurodegeneration is directly interwoven with the progression of HF. Biomarkers of neurodegeneration, particularly NfL, may help identify patients potentially profiting from a comprehensive neurological work-up. Further research is necessary to test whether early diagnosis or optimized HFrEF treatment can preserve cognitive function.

Impact of interrupting antiretroviral therapy started during primary HIV-1 infection on plasma neurofilament light chain protein, a marker of neuronal injury: The SPARTAC trial

Objective

Antiretroviral therapy (ART)-conferred suppression of HIV replication limits neuronal injury and inflammation. ART interruption tests efficacy in HIV cure trials and viral rebound after ART interruption may induce neuronal injury. We investigated the impact of protocol-defined ART interruption, commenced during primary HIV-1 infection (PHI) on a biomarker of neuro-axonal injury (neurofilament light protein (NfL)), and its associations with inflammation (D-dimer and interleukin-6 (IL-6)) and HIV-1 reservoir size (total HIV-1 DNA).

Design

Retrospective study measuring plasma NfL in 83 participants enrolled in SPARTAC randomised to receive 48-weeks ART initiated during PHI, followed by ART interruption.

Methods

NfL (Simoa immunoassay, Quanterix™) was measured before ART, after 48 weeks on ART, and 12 weeks after stopping ART. Plasma D-dimer and IL-6, and total HIV-1 DNA in peripheral CD4+ T-cells results were available in a subset of participants. Longitudinal NfL changes were assessed using mixed models, and associations with clinical and laboratory parameters using linear regression.

Results

NfL decreased following 48-weeks ART (geometric mean 6.9 to 5.8 pg/mL, p = 0.006) with no further significant change up to 12-weeks post-stopping ART despite viral rebound in the majority of participants (median 1.7 to 3.9 plasma HIV-1 RNA log10 copies/mL). Higher baseline NfL was independently associated with higher plasma HIV-1 RNA (p = 0.020) and older age (p = 0.002). While NfL was positively associated with D-dimer (n = 48; p = 0.002), there was no significant association with IL-6 (n = 48) or total HIV-1 DNA (n = 51).

Conclusions

Using plasma NfL as a surrogate marker, a decrease in neuro-axonal injury was observed in a cohort of participants following ART initiation during PHI, with no evidence of neuro-axonal injury rebound following ART interruption for up to 12 weeks, despite viral rebound in the majority of participants.

Plasma biomarkers increase diagnostic confidence in patients with Alzheimer's disease or frontotemporal lobar degeneration

BACKGROUND

The recent development of techniques to assess plasma biomarkers has changed the way the research community envisions the future of diagnosis and management of Alzheimer's disease (AD) and other neurodegenerative disorders. This work aims to provide real world evidence on the clinical impact of plasma biomarkers in an academic tertiary care center.

METHODS

Anonymized clinical reports of patients diagnosed with AD or Frontotemporal Lobar Degeneration with available plasma biomarkers (Aβ42, Aβ42/Aβ40, p-tau181, p-tau231, NfL, GFAP) were independently assessed by two neurologists who expressed diagnosis and diagnostic confidence three times: (T0) at baseline based on the information collected during the first visit, (T1) after plasma biomarkers, and (T2) after traditional biomarkers (when available). Finally, we assessed whether clinicians' interpretation of plasma biomarkers and the consequent clinical impact are consistent with the final diagnosis, determined after the conclusion of the diagnostic clinical and instrumental work-up by the actual managing physicians who had complete access to all available information.

RESULTS

Clinicians assessed 122 reports, and their concordance ranged from 81 to 91% at the three time points. At T1, the presentation of plasma biomarkers resulted in a change of diagnosis in 2% (2/122, p = 1.00) of cases, and in increased diagnostic confidence in 76% (91/120, p < 0.001) of cases with confirmed diagnosis. The change in diagnosis and the increase in diagnostic confidence after plasma biomarkers were consistent with the final diagnosis in 100% (2/2) and 81% (74/91) of cases, respectively. At T2, the presentation of traditional biomarkers resulted in a further change of diagnosis in 13% (12/94, p = 0.149) of cases, and in increased diagnostic confidence in 88% (72/82, p < 0.001) of cases with confirmed diagnosis.

CONCLUSIONS

In an academic tertiary care center, plasma biomarkers supported clinicians by increasing their diagnostic confidence in most cases, despite a negligible impact on diagnosis. Future prospective studies are needed to assess the full potential of plasma biomarkers on clinical grounds.

Plasma neurofilament light chain is not elevated in people with first-episode psychosis or those at ultra-high risk for psychosis

INTRODUCTION

Neurofilament light chain (NfL), a blood biomarker of neuronal injury, shows promise in distinguishing neurodegenerative disorders from psychiatric conditions. This is especially relevant in psychosis, given neurological conditions such as autoimmune encephalitis and Niemann Pick Type C disease (NPC) may initially present with psychotic symptoms. Whilst NfL levels have been studied in established schizophrenia cases, their levels in first-episode psychosis (FEP) and ultra-high risk (UHR) for psychosis individuals remain largely unexplored. This study aimed to compare plasma NfL in people with FEP or UHR with healthy controls, as well as explore its associations with clinical data.

METHOD

We retrospectively analysed plasma NfL in 63 participants, consisting of 29 individuals with FEP, 10 individuals with UHR, and 24 healthy controls. We used general linear models (GLM), which were bootstrapped, to compute bias-corrected and accelerated (BCa) 95 % confidence intervals (CIs).

RESULTS

Mean NfL levels were 5.2 pg/mL in FEP, 4.9 pg/mL in UHR, and 5.9 pg/mL in healthy controls. Compared to healthy controls, there were no significant differences in NfL levels in the FEP group (β = -0.22, 95 % CI [-0.86, 0.39], p = 0.516) nor UHR group (β = -0.37, 95 % CI [-0.90, 0.19], p = 0.182). There were no significant associations between NfL levels and clinical variables in the FEP group.

DISCUSSION

Our study is the first to demonstrate that plasma NfL levels are not significantly elevated in individuals at UHR for psychosis compared to healthy controls, a finding also observed in the FEP cohort. These findings bolster the potential diagnostic utility of NfL in differentiating between psychiatric and neurodegenerative disorders.

Serum neurofilament light for detecting disease activity in individual patients in multiple sclerosis: A 48-week prospective single-center study

BACKGROUND

Serum neurofilament light (sNfL) reflects neuroaxonal damage and is now used as an outcome in treatment trials of relapsing-remitting multiple sclerosis (RRMS). However, the diagnostic properties of sNfL for monitoring disease activity in individual patients warrant further investigations.

METHOD

Patients with suspected relapse and/or contrast-enhancing lesions (CELs) were consecutively included and performed magnetic resonance imaging (MRI) of the brain at baseline and weeks 28 and 48. Serum was obtained at baseline and 2, 4, 8, 16, 24, and 48 weeks. Neurofilament light concentration was measured using Single molecule array technology.

RESULTS

We included 44 patients, 40 with RRMS and 4 with clinically isolated syndrome. The median sNfL level peaked at 2 weeks post-baseline (14.6 ng/L, interquartile range (IQR); 9.3-31.6) and reached nadir at 48 weeks (9.1 ng/L, IQR; 5.5-15.0), equivalent to the median sNfL of controls (9.1 ng/L, IQR; 7.4-12). A baseline Z-score of more than 1.1 (area under the curve; 0.78, p < 0.0001) had a sensitivity of 81% and specificity of 70% to detect disease activity.

CONCLUSION

One out of five patients with relapse and/or CELs did not change significantly in post-baseline sNfL levels. The utility of repeated sNfL measurements to monitor disease activity is complementary rather than a substitute for clinical and MRI measures.

Serum neurofilament light chain associates with symptom burden in Lyme neuroborreliosis patients: a longitudinal cohort study from Norway

OBJECTIVES

Serum neurofilament light chain (sNfL), an indicator of neuronal damage, is increasingly recognized as a potential biomarker for disease activity in neurodegenerative disorders. In this study, we wanted to investigate sNfL as a prognostic marker in a large, well-defined population of 90 patients with Lyme neuroborreliosis (LNB). In addition, we sought to explore associations between symptoms and sNfL levels during the acute phase of LNB.

MATERIALS AND METHODS

Patients diagnosed with definite or possible LNB were recruited from a double-blinded, placebo-controlled, multi-center trial, in which the participants were randomly assigned to 2 or 6 weeks of oral doxycycline treatment. The sNfL levels were measured using a single molecule array assay at both diagnosis and 6-month follow-up, and analysed against clinical parameters, variations in symptom burden and long-term complaints as assessed by a composite clinical score.

RESULTS

At the time of diagnosis, approximately 60% of the patients had elevated sNfL levels adjusted for age. Notably, mean sNfL levels were significantly higher at diagnosis (52 pg/ml) compared to 6 months after treatment (12 pg/ml, p < 0.001), when sNfL levels had normalized in the majority of patients. Patients with objective signs of spinal radiculitis had significantly higher baseline sNfL levels compared to patients without spinal radiculitis (p = 0.033).

CONCLUSION

Our findings suggest that sNfL can serve as a biomarker for peripheral nerve tissue involvement in the acute phase of LNB. As found in an earlier study, we confirm normalization of sNfL levels in blood after treatment. We found no prognostic value of acute-phase sNfL levels on patient outcome.

Neurofilaments as biomarkers in neurological disorders - towards clinical application

Neurofilament proteins have been validated as specific body fluid biomarkers of neuro-axonal injury. The advent of highly sensitive analytical platforms that enable reliable quantification of neurofilaments in blood samples and simplify longitudinal follow-up has paved the way for the development of neurofilaments as a biomarker in clinical practice. Potential applications include assessment of disease activity, monitoring of treatment responses, and determining prognosis in many acute and chronic neurological disorders as well as their use as an outcome measure in trials of novel therapies. Progress has now moved the measurement of neurofilaments to the doorstep of routine clinical practice for the evaluation of individuals. In this Review, we first outline current knowledge on the structure and function of neurofilaments. We then discuss analytical and statistical approaches and challenges in determining neurofilament levels in different clinical contexts and assess the implications of neurofilament light chain (NfL) levels in normal ageing and the confounding factors that need to be considered when interpreting NfL measures. In addition, we summarize the current value and potential clinical applications of neurofilaments as a biomarker of neuro-axonal damage in a range of neurological disorders, including multiple sclerosis, Alzheimer disease, frontotemporal dementia, amyotrophic lateral sclerosis, stroke and cerebrovascular disease, traumatic brain injury, and Parkinson disease. We also consider the steps needed to complete the translation of neurofilaments from the laboratory to the management of neurological diseases in clinical practice.

Plasma GFAP, NfL and pTau 181 detect preclinical stages of dementia

Background

Plasma biomarkers are preferable to invasive and expensive diagnostic tools, such as neuroimaging and lumbar puncture that are gold standard in the clinical management of Alzheimer's Disease (AD). Here, we investigated plasma Glial Fibrillary Acidic Protein (GFAP), Neurofilament Light Chain (NfL) and Phosphorylated-tau-181 (pTau 181) in AD and in its early stages: Subjective cognitive decline (SCD) and Mild cognitive impairment (MCI).

Material and methods

This study included 152 patients (42 SCD, 74 MCI and 36 AD). All patients underwent comprehensive clinical and neurological assessment. Blood samples were collected for Apolipoprotein E (APOE) genotyping and plasma biomarker (GFAP, NfL, and pTau 181) measurements. Forty-three patients (7 SCD, 27 MCI, and 9 AD) underwent a follow-up (FU) visit after 2 years, and a second plasma sample was collected. Plasma biomarker levels were detected using the Simoa SR-X technology (Quanterix Corp.). Statistical analysis was performed using SPSS software version 28 (IBM SPSS Statistics). Statistical significance was set at p < 0.05.

Results

GFAP, NfL and pTau 181 levels in plasma were lower in SCD and MCI than in AD patients. In particular, plasma GFAP levels were statistically significant different between SCD and AD (p=0.003), and between MCI and AD (p=0.032). Plasma NfL was different in SCD vs MCI (p=0.026), SCD vs AD (p<0.001), SCD vs AD FU (p<0.001), SCD FU vs AD (p=0.033), SCD FU vs AD FU (p=0.011), MCI vs AD (p=0.002), MCI FU vs AD (p=0.003), MCI FU vs AD FU (p=0.003) and MCI vs AD FU (p=0.003). Plasma pTau 181 concentration was significantly different between SCD and AD (p=0.001), MCI and AD (p=0.026), MCI FU and AD (p=0.020). In APOE ϵ4 carriers, a statistically significant increase in plasma NfL (p<0.001) and pTau 181 levels was found (p=0.014). Moreover, an association emerged between age at disease onset and plasma GFAP (p = 0.021) and pTau181 (p < 0.001) levels.

Discussion and conclusions

Plasma GFAP, NfL and pTau 181 are promising biomarkers in the diagnosis of the prodromic stages and prognosis of dementia.

Plasma brain-derived tau is an amyloid-associated neurodegeneration biomarker in Alzheimer's disease

Staging amyloid-beta (Aβ) pathophysiology according to the intensity of neurodegeneration could identify individuals at risk for cognitive decline in Alzheimer's disease (AD). In blood, phosphorylated tau (p-tau) associates with Aβ pathophysiology but an AD-type neurodegeneration biomarker has been lacking. In this multicenter study (n = 1076), we show that brain-derived tau (BD-tau) in blood increases according to concomitant Aβ ("A") and neurodegeneration ("N") abnormalities (determined using cerebrospinal fluid biomarkers); We used blood-based A/N biomarkers to profile the participants in this study; individuals with blood-based p-tau+/BD-tau+ profiles had the fastest cognitive decline and atrophy rates, irrespective of the baseline cognitive status. Furthermore, BD-tau showed no or much weaker correlations with age, renal function, other comorbidities/risk factors and self-identified race/ethnicity, compared with other blood biomarkers. Here we show that blood-based BD-tau is a biomarker for identifying Aβ-positive individuals at risk of short-term cognitive decline and atrophy, with implications for clinical trials and implementation of anti-Aβ therapies.

Brain magnetic resonance imaging findings six months after critical COVID-19: A prospective cohort study

BACKGROUND

COVID-19 patients suffered from neurological symptoms in the acute phase. Whether this led to long-term consequences was unknown. We studied long-term brain MRI findings in ICU-treated COVID-19 patients and compared them with findings in groups with less severe acute disease.

MATERIALS AND METHODS

In this prospective cohort study, 69 ICU-treated, 46 ward-treated, and 46 home-isolated patients, as well as 53 non-COVID-19 controls, underwent brain MRI six months after acute COVID-19. Plasma neurofilament light chain (NfL), a biomarker of neuroaxonal injury, was measured simultaneously.

RESULTS

Ischaemic infarctions existed in 5.8% of ICU-treated patients. Cerebral microbleeds (CMBs) existed in 27 (39.1%) ICU-treated, 13 (28.3%) ward-treated, 8 (17.4%) home-isolated COVID-19 patients, and 12 (22.6%) non-COVID controls. Patients with CMBs were older (p < 0.001), had a higher level of plasma NfL (p = 0.003), and higher supplementary oxygen days (p < 0.001). In multivariable analysis, age (OR 1.06, 95% CI 1.02-1.09) and supplementary oxygen days (OR 1.07, 95% CI 1.02-1.13) were associated with CMBs. The ICU group showed prevalent distribution of CMBs in deep regions.

CONCLUSION

Age and supplementary oxygen days were independently associated with CMBs; COVID-19 status showed no association. Accumulation of risk factors in the ICU group may explain the higher prevalence of CMBs.

TRIAL REGISTRATION

ClinicalTrials.govNCT04864938, registered February 9, 2021.

A critical appraisal of blood-based biomarkers for Alzheimer's disease

Biomarkers that predict the clinical onset of Alzheimer's disease (AD) enable the identification of individuals in the early, preclinical stages of the disease. Detecting AD at this point may allow for more effective therapeutic interventions and optimized enrollment for clinical trials of novel drugs. The current biological diagnosis of AD is based on the AT(N) classification system with the measurement of brain deposition of amyloid-β (Aβ) ("A"), tau pathology ("T"), and neurodegeneration ("N"). Diagnostic cut-offs for Aβ1-42, the Aβ1-42/Aβ1-40 ratio, tau and hyperphosphorylated-tau concentrations in cerebrospinal fluid have been defined and may support AD clinical diagnosis. Blood-based biomarkers of the AT(N) categories have been described in the AD continuum. Cross-sectional and longitudinal studies have shown that the combination of blood biomarkers tracking neuroaxonal injury (neurofilament light chain) and neuroinflammatory pathways (glial fibrillary acidic protein) enhance sensitivity and specificity of AD clinical diagnosis and improve the prediction of AD onset. However, no international accepted cut-offs have been identified for these blood biomarkers. A kit for blood Aβ1-42/Aβ1-40 is commercially available in the U.S.; however, it does not provide a diagnosis, but simply estimates the risk of developing AD. Although blood-based AD biomarkers have a great potential in the diagnostic work-up of AD, they are not ready for the routine clinical use.

Biomarkers of Alzheimer's disease and neurodegeneration in dried blood spots-A new collection method for remote settings

BACKGROUND

We aimed to evaluate the precision of Alzheimer's disease (AD) and neurodegeneration biomarker measurements from venous dried plasma spots (DPSv enous) for the diagnosis and monitoring of neurodegenerative diseases in remote settings.

METHODS

In a discovery (n = 154) and a validation cohort (n = 115), glial fibrillary acidic protein (GFAP); neurofilament light (NfL); amyloid beta (Aβ) 40, Aβ42; and phosphorylated tau (p-tau181 and p-tau217) were measured in paired DPSvenous and ethylenediaminetetraacetic acid plasma samples with single-molecule array. In the validation cohort, a subset of participants (n = 99) had cerebrospinal fluid (CSF) biomarkers.

RESULTS

All DPSvenous and plasma analytes correlated significantly, except for Aβ42. In the validation cohort, DPSvenous GFAP, NfL, p-tau181, and p-tau217 differed between CSF Aβ-positive and -negative individuals and were associated with worsening cognition.

DISCUSSION

Our data suggest that measuring blood biomarkers related to AD pathology and neurodegeneration from DPSvenous extends the utility of blood-based biomarkers to remote settings with simplified sampling conditions, storage, and logistics.

HIGHLIGHTS

A wide array of biomarkers related to Alzheimer's disease (AD) and neurodegeneration were detectable in dried plasma spots (DPSvenous). DPSvenous biomarkers correlated with standard procedures and cognitive status. DPSvenous biomarkers had a good diagnostic accuracy discriminating amyloid status. Our findings show the potential interchangeability of DPSvenous and plasma sampling. DPSvenous may facilitate remote and temperature-independent sampling for AD biomarker measurement. Innovative tools for blood biomarker sampling may help recognizing the earliest changes of AD.

Pediatric reference intervals for serum neurofilament light and glial fibrillary acidic protein using the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort

OBJECTIVES

Blood biomarkers have the potential to transform diagnosis and prognosis for multiple neurological indications. Establishing normative data is a critical benchmark in the analytical validation process. Normative data are important in children as little is known about how brain development may impact potential biomarkers. The objective of this study is to generate pediatric reference intervals (RIs) for serum neurofilament light (NfL), an axonal marker, and glial fibrillary acidic protein (GFAP), an astrocytic marker.

METHODS

Serum from healthy children and adolescents aged 1 to <19 years were obtained from the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort. Serum NfL (n=300) and GFAP (n=316) were quantified using Simoa technology, and discrete RI (2.5th and 97.5th percentiles) and continuous RI (5th and 95th percentiles) were generated.

RESULTS

While there was no association with sex, there was a statistically significant (p<0.0001) negative association between age and serum NfL (Rho -0.400) and GFAP (Rho -0.749). Two statistically significant age partitions were generated for NfL: age 1 to <10 years (lower, upper limit; 3.13, 20.6 pg/mL) and 10 to <19 years (1.82, 7.44 pg/mL). For GFAP, three statistically significant age partitions were generated: age 1 to <3.5 years (80.4, 601 pg/mL); 3.5 to <11 years (50.7, 224 pg/mL); and 11 to <19 years (26.2, 119 pg/mL).

CONCLUSIONS

Taken together with the literature on adults, NfL and GFAP display U-shaped curves with high levels in infants, decreasing levels during childhood, a plateau during adolescence and early adulthood and increasing levels in seniors. These normative data are expected to inform future pediatric studies on the importance of age on neurological blood biomarkers.

An EWAS of dementia biomarkers and their associations with age, African ancestry, and PTSD

BACKGROUND

Large-scale cohort and epidemiological studies suggest that PTSD confers risk for dementia in later life but the biological mechanisms underlying this association remain unknown. This study examined this question by assessing the influences of PTSD, APOE ε4 genotypes, DNA methylation, and other variables on the age- and dementia-associated biomarkers Aβ40, Aβ42, GFAP, NfL, and pTau-181 measured in plasma. Our primary hypothesis was that PTSD would be associated with elevated levels of these markers.

METHODS

Analyses were based on data from a PTSD-enriched cohort of 849 individuals. We began by performing factor analyses of the biomarkers, the results of which identified a two-factor solution. Drawing from the ATN research framework, we termed the first factor, defined by Aβ40 and Aβ42, "Factor A" and the second factor, defined by GFAP, NfL and pTau-181, "Factor TN." Next, we performed epigenome-wide association analyses (EWAS) of the two-factor scores. Finally, using structural equation modeling (SEM), we evaluated (a) the influence of PTSD, age, APOE ε4 genotype and other covariates on levels of the ATN factors, and (b) tested the mediating influence of the EWAS-significant DNAm loci on these associations.

RESULTS

The Factor A EWAS identified one significant locus, cg13053408, in FANCD2OS. The Factor TN analysis identified 3 EWAS-significant associations: cg26033520 near ASCC1, cg23156469 in FAM20B, and cg15356923 in FAM19A4. The SEM showed age to be related to both factors, more so with Factor TN (β = 0.581, p < 0.001) than Factor A (β = 0.330, p < 0.001). Genotype-determined African ancestry was associated with lower Factor A (β = 0.196, p < 0.001). Contrary to our primary hypothesis, we found a modest negative bivariate correlation between PTSD and the TN factor scores (r = - 0.133, p < 0.001) attributable primarily to reduced levels of GFAP (r = - 0.128, p < 0.001).

CONCLUSIONS

This study identified novel epigenetic associations with ATN biomarkers and demonstrated robust age and ancestral associations that will be essential to consider in future efforts to develop the clinical applications of these tests. The association between PTSD and reduced GFAP, which has been reported previously, warrants further investigation.

Comparison of CSF and plasma NfL and pNfH for Alzheimer's disease diagnosis: a memory clinic study

Plasma neurofilament light chain (NfL) is a promising biomarker of axonal damage for the diagnosis of neurodegenerative diseases. Phosphorylated neurofilament heavy chain (pNfH) has demonstrated its value in motor neuron diseases diagnosis, but has less been explored for dementia diagnosis. In a cross-sectional study, we compared cerebrospinal fluid (CSF) and plasma NfL and pNfH levels in n = 188 patients from Lariboisière Hospital, Paris, France, including AD patients at mild cognitive impairment stage (AD-MCI, n = 36) and dementia stage (n = 64), non-AD MCI (n = 38), non-AD dementia (n = 28) patients and control subjects (n = 22). Plasma NfL, plasma and CSF pNfH levels were measured using Simoa and CSF NfL using ELISA. The correlation between CSF and plasma levels was stronger for NfL than pNfH (rho = 0.77 and rho = 0.52, respectively). All neurofilament markers were increased in AD-MCI, AD dementia and non-AD dementia groups compared with controls. CSF NfL, CSF pNfH and plasma NfL showed high performance to discriminate AD at both MCI and dementia stages from control subjects [AUC (area under the curve) = 0.82-0.91]. Plasma pNfH displayed overall lower AUCs for discrimination between groups compared with CSF pNfH. Neurofilament markers showed similar moderate association with cognition. NfL levels displayed significant association with mediotemporal lobe atrophy and white matter lesions in the AD group. Our results suggest that CSF NfL and pNfH as well as plasma NfL levels display equivalent performance in both positive and differential AD diagnosis in memory clinic settings. In contrast to motoneuron disorders, plasma pNfH did not demonstrate added value as compared with plasma NfL.

Plasma biomarkers of Alzheimer's disease and related dementias in American Indians: The Strong Heart Study

INTRODUCTION

Identification of Alzheimer's disease (AD) needs inexpensive, noninvasive biomarkers, with validation in all populations.

METHODS

We collected plasma markers in older American Indian individuals: phosphorylated-tau181 (pTau181); amyloid-beta (Aβ) 40,42; glial fibrillary acidic protein (GFAP); and neurofilament light chain (NfL). Plasma markers were analyzed for discriminant properties with cognitive status and etiology using receiver operating characteristic (ROC) analysis.

RESULTS

PTau181, GFAP, NfL plasma values were significantly associated with cognition, but Aβ were not. Discriminant performance was moderate for individual markers, with pTau181, GFAP, NfL performing best, but an empirically selected panel of markers (age, sex, education, pTau181, GFAP, NfL, Aβ4240 ratio) had excellent discriminant performance (AUC > 0.8).

DISCUSSION

In American Indian individuals, pTau181 and Aβ values suggested more common pathology than in majority populations. Aβ was less informative than in other populations; however, all four markers were needed for a best-performing dementia diagnostic model. These data validate utility of AD plasma markers, while suggesting population-specific diagnostic characteristics.

Biological variation estimates of Alzheimer's disease plasma biomarkers in healthy individuals

INTRODUCTION

Blood biomarkers have proven useful in Alzheimer's disease (AD) research. However, little is known about their biological variation (BV), which improves the interpretation of individual-level data.

METHODS

We measured plasma amyloid beta (Aβ42, Aβ40), phosphorylated tau (p-tau181, p-tau217, p-tau231), glial fibrillary acidic protein (GFAP), and neurofilament light chain (NfL) in plasma samples collected weekly over 10 weeks from 20 participants aged 40 to 60 years from the European Biological Variation Study. We estimated within- (CVI ) and between-subject (CVG ) BV, analytical variation, and reference change values (RCV).

RESULTS

Biomarkers presented considerable variability in CVI and CVG . Aβ42/Aβ40 had the lowest CVI (≈ 3%) and p-tau181 the highest (≈ 16%), while others ranged from 6% to 10%. Most RCVs ranged from 20% to 30% (decrease) and 25% to 40% (increase).

DISCUSSION

BV estimates for AD plasma biomarkers can potentially refine their clinical and research interpretation. RCVs might be useful for detecting significant changes between serial measurements when monitoring early disease progression or interventions. Highlights Plasma amyloid beta (Aβ42/Aβ40) presents the lowest between- and within-subject biological variation, but also changes the least in Alzheimer's disease (AD) patients versus controls. Plasma phosphorylated tau variants significantly vary in their within-subject biological variation, but their substantial fold-changes in AD likely limits the impact of their variability. Plasma neurofilament light chain and glial fibrillary acidic protein demonstrate high between-subject variation, the impact of which will depend on clinical context. Reference change values can potentially be useful in monitoring early disease progression and the safety/efficacy of interventions on an individual level. Serial sampling revealed that unexpectedly high values in heathy individuals can be observed, which urges caution when interpreting AD plasma biomarkers based on a single test result.