Development of a Highly Sensitive Neurofilament Light Chain Assay on an Automated Immunoassay Platform

The utility of serum neurofilament light chain in MOGAD: Current insights and future directions

BACKGROUND

Serum neurofilament light chain (sNfL) has become an increasingly established biomarker for monitoring in multiple sclerosis (MS). Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a demyelinating disorder distinct from MS in terms of pathophysiology and treatment options, also presenting with demyelinating attacks that can result in permanent disability. Given its unpredictable disease course, the need for biomarkers reflective of the risk for poor clinical recovery or relapsing course is pressing. The purpose of this review is to summarize the current knowledge on sNfL levels in people with MOGAD, assess their utility for clinical practice and gain insights for future research.

METHODS

Embase, MEDLINE, Scopus, and CINAHL databases were searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. Keywords used in the search included: (myelin oligodendrocyte glycoprotein OR MOG OR MOGAD) AND (neurofilament* OR neuro filament* OR NfL OR sNfL). This initial search generated 195 reports, 23 of which were original research articles investigating NfL levels in MOGAD patients, therefore meeting our inclusion criteria.

RESULTS

422 MOGAD patients were involved across all studies. Most studies revealed higher sNfL in MOGAD patients (n = 292) than in healthy controls (n = 3,172) with one study finding higher sNfL in MOGAD only during relapse. sNfL levels during attacks were similar when comparing MOGAD (n = 94) to MS (n = 256) and MOGAD (n = 149) to APQ4+ neuromyelitis optica spectrum disorder (APQ4+ NMOSD) (n = 214). MOGAD patients with brain lesions on magnetic resonance imaging (MRI) during a recent attack (n = 69 samples) had higher sNfL levels than patients without brain lesions (n = 78 samples). Median sNfL concentration was higher following clinical attacks (n = 69 samples) than in remission (n = 83 samples) in 3/5 studies. sNfL were higher at disease onset than subsequent attacks in 2 studies (n = 133 samples). Onset sNfL levels were not predictive of the likelihood of future relapse (relapsing: n = 15, monophasic: n = 18). A positive correlation was found between sNfL levels and attack severity assessed through various disability scales (n = 202), but not with the severity of acute or residual visual acuity (n = 45 eyes), or with residual retinal thickness among subjects with the optic neuritis (ON) phenotype (n = 11 eyes). The sGFAP/sNfL ratio showed utility in discriminating MOGAD from other autoimmune demyelinating diseases in two studies (MOGAD: n = 56, APQ4+ NMOSD: n = 66, MS: n = 31).

DISCUSSION

sNfL levels at presentation have limited utility in distinguishing MOGAD from other demyelinating disorders, but their combination with other biomarkers might improve their diagnostic utility. sNfL levels are higher in brain/spinal cord presentations than optic neuritis, correlating with clinical severity of these phenotypes but less so with the severity of visual outcome. Further studies should clarify the utility of sNfL as a biomarker for MOGAD, particularly in relation to long-term outcomes and imaging markers of central nervous system damage. Standardized sNfL testing parameters will improve study comparability and clinical application.

Neurofilament Light Chain and Multiple Sclerosis: Building a Neurofoundational Model of Biomarkers and Diagnosis

Neurofilament light chain (NfL), an abundant cytoskeletal protein in neurons, has emerged as a promising serum biomarker that indicates non-specific neuronal damage secondary to various neurologic diseases, including multiple sclerosis (MS). Emerging evidence suggests that serum NfL levels correlate with future disability, brain atrophy, predict new disease activity, and decrease in response to various disease-modifying therapies. As research continues to validate NfL's potential role in clinical practice, the need for a practical model to conceptualize and visualize its relevance to MS pathology becomes evident-not only for healthcare providers but also for patients. To address this, we propose the Neurofoundational Model (NFM), which likens a neuron to a home, with various parts of the home representing distinct regions of the central nervous system (CNS). In this model, the home (neuron) experiences scenarios such as a fire, an earthquake, and a slow flood, representing distinct MS disease states. A fire illustrates an MS relapse with good recovery, where serum NfL levels rise during the relapse and subsequently return near baseline. An earthquake represents an MS relapse with poor recovery, where NfL levels increase and remain elevated above baseline. Finally, a slow flood depicts MS in progressive stages, characterized by sustained and gradually increasing serum NfL levels without abrupt clinical changes. This approach offers a clear and relatable visualization for clinicians and patients alike, illustrating the dynamics of serum NfL levels during CNS damage caused by demyelination. By integrating this model into clinical practice, we aim to enhance understanding and communication regarding the role of NfL in MS pathology and its potential utility as a biomarker.

Unveiling amyotrophic lateral sclerosis complexity: insights from proteomics, metabolomics and microbiomics

Amyotrophic lateral sclerosis is the most common motor neuron disease and manifests as a clinically and genetically heterogeneous neurodegenerative disorder mainly affecting the motor systems. To date, despite promising results and accumulating knowledge on the pathomechanisms of amyotrophic lateral sclerosis, a specific disease-modifying treatment is still not available. In vitro and in vivo disease models coupled with multiomics techniques have helped elucidate the pathomechanisms underlying this disease. In particular, omics approaches are powerful tools for identifying new potential disease biomarkers that may be particularly useful for diagnosis, prognosis and assessment of treatment response. In turn, these findings could support physicians in stratifying patients into clinically relevant subgroups for the identification of the best therapeutic targets. Here, we provide a comprehensive review of the most relevant literature highlighting the importance of proteomics approaches in determining the role of pathogenic misfolded/aggregated proteins and the molecular mechanisms involved in the pathogenesis and progression of amyotrophic lateral sclerosis. In addition, we explored new findings arising from metabolomic and lipidomic studies, which can aid to elucidate the intricate metabolic alterations underlying amyotrophic lateral sclerosis pathology. Moreover, we integrated these insights with microbiomics data, providing a thorough understanding of the interplay between metabolic dysregulation and microbial dynamics in disease progression. Indeed, a greater integration of these multiomics data could lead to a deeper understanding of disease mechanisms, supporting the development of specific therapies for amyotrophic lateral sclerosis.

Advances in neurofilament light chain analysis

This chapter provides a comprehensive summary of clinical laboratory testing for neurofilament light chain (NfL) in neurologic disease. A primer on the NfL structure and function is presented with its potential use as a biomarker. The most widely utilized methods for NfL in biologic samples are highlighted and examined. Limitations of current knowledge are considered, as are outstanding questions related to dissemination and standardization of testing. Herein we focus on methods available today and those in development for clinical use. In the final section, a broad vision is presented of how NfL may be utilized in the future to improve diagnosis and treatment of neurologic diseases as well as for maintaining health.

Association between serum neurofilament light chains and depression: A cross-sectional study based on NHANES 2013-2014 database

BACKGROUND

Serum neurofilament light chain (sNfl), identified as a promising biomarker, is a protein released into the bloodstream post-axonal damage. Studies on its correlation with depression, however, remains scarce. The purpose of this study was to investigate the potential relationship between sNfL levels and risk of depression among a representative segment of the U. S. populace.

METHODS

This study included 1,909 participants from the 2013-2014 National Health and Nutrition Examination Survey. The 9-item Patient Health Questionnaire (PHQ-9 scale) assessed depression symptoms, while sNfl concentrations were measured using the Attelica fully automated immunoassay system. The logistic regression, restricted cubic splines (RCS), and subgroup analysis were performed to assess the relationship between sNfL, lnsNfL (log-transformed values of sNfl), and depression.

RESULTS

After adjusting for sociodemographic variables, lifestyle, and chronic conditions, sNfl and lnsNfL levels positively correlated with depression. A unit increase in sNfL and lnsNfL levels was linked to a 0.7 % and 33.8 % rise in depression risk, respectively [OR (95 % CI): 1.007 (1.000, 1.014), p = 0.041 for sNfl; 1.338 (1.015, 1.764), p = 0.039 for lnsNfl]. Additionally, a positive linear association was observed between lnsNfl levels and the risk of depression (p for overall = 0.039, p for nonlinear = 0.189 in RCS). No significant differences were observed across subgroups between lnsNfl and depression, with no significant impact on this relationship from subgroups (All p for interaction >0.05).

CONCLUSION

The findings of our study suggest a significant positive correlation between sNfl and depression, warranting further investigation into the molecular dynamics linking sNfL to depression and subgroup variability.

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.

Relationship between serum neurofilament light chain protein and depression: A nationwide survey and Mendelian randomization study

BACKGROUND

Investigating the link between serum neurofilament protein (sNfL) levels and depression remains an area of limited understanding. This study explores the correlation in US adults and employs Mendelian randomization (MR) to ascertain causality.

METHODS

Our cross-sectional study analyzed data from participants aged 20 and above in the National Health and Nutrition Examination Survey (2013-2014). We employed a weighted multiple logistic regression model to examine the relationship between ln (sNfL) and depression. Restricted cubic splines (RCS) were used to visualize non-linear relationships. Stratified analyses examined associations between ln(sNfL) and depression in different subgroups. Subsequently, we conducted a two-sample bidirectional Mendelian randomization (MR) to assess the causal relationship between sNfL and depression. The inverse variance-weighted (IVW) method was utilized as the primary analysis.

RESULTS

Among 1765 participants (mean age 45.19 years; 49.37 % male), 166 had depression with a Patient Health Questionnaire (PHQ-9) score ≥ 10. After adjusting for covariates, a positive correlation remained between sNfL and depression (OR 1.511, 95 % CI: 1.050-2.175). RCS curves indicated a non-linear association, with a turning point at 2.76 pg/ml. Stratified analyses revealed positive correlations in specific subgroups, with interactions involving age, race, family income, recreational activity, and ln(sNfL). MR using IVW found no significant causal relationship between sNfL and depression genetically (OR = 0.956, 95 % CI: 0.878-1.042), with reverse analysis yielding similar results (OR = 0.897, 95 % CI: 0.756-1.065).

CONCLUSIONS

This cross-sectional study highlights a significant correlation between ln(sNfL) and depression. However, MR results indicate no causal relationship between sNfL and depression.

Neurofilament light in serum: Reference values and effect of risk factors for multiple sclerosis

BACKGROUND

The measurement of neurofilament light (NFL) in blood samples has been established as a sensitive measure of neuroaxonal damage in a wide range of diseases in the peripheral and central nervous system, including multiple sclerosis (MS). Previous studies have identified confounding factors that may influence the serum concentration of NFL.

AIM

We aimed at investigating the relationship between known confounders (age, body mass index, blood volume) and risk factors for MS (smoking and human leukocyte antigen (HLA)) on serum concentrations of NFL in control subjects. In addition, we compared different methods for correction for confounders when applied to newly diagnosed patients with MS.

METHODS

We measured serum concentrations of NFL by single molecule array analysis in 1.101 control subjects without neurological disease from 4 different cohorts (including 906 healthy blood donors) and 72 patients with newly diagnosed relapsing-remitting MS. A questionnaire on smoking habits was distributed to the 906 healthy blood donors, and the HLA risk alleles HLA-DRB1*15:01 and HLA-A*02:01 were genotyped by TaqMan allelic-discrimination PCR analysis in these subjects.

RESULTS

We confirmed that serum concentrations of NFL increase with age, but we also found that sample storage conditions for the different cohorts of control subjects had a substantial effect. Prolonged storage time and storage at -20° were independently associated with lower serum concentrations of NFL than shorter storage time and storage at -80° In samples from the large cohort of blood donors, we confirmed an association between high BMI and high blood volume with lower serum concentrations of NFL and found that this association was marginally stronger for BMI than for blood volume. We found no association between smoking and HLA risk factors for MS with serum concentrations of NFL in the blood donor cohort. Finally, we found that a simple method for correcting for the effect of age on NFL performed as well as Z-scores, which consider the effect of both age and BMI. This was shown when discriminating between patients with MS and control subjects and between MS patients with and without Gd-enhancing MRI lesions.

CONCLUSIONS

We confirm an association between serum concentrations of NFL, age, and BMI, but we also find that it may often be sufficient to correct for the effect of age alone. The effect of BMI should, however, be considered along with the effect of other confounding factors, including various comorbidities.

All-Cause Mortality Differentials by Diabetes Status and Serum Neurofilament Light-Chain Levels in US General Adults

CONTEXT

Neurofilament light chains (sNFLs) increase in patients with diabetes (DM) and are associated with death.

OBJECTIVE

This work aimed to examine whether sNFL mediates associations of DM with all-cause mortality and the extent of interaction or joint relations of sNFL and DM with mortality.

METHODS

This population-based cohort study was conducted using the 2013 to 2014 cycle of the National Health and Nutrition Examination Survey. A total of 2071 adults aged 20 to 75 years with sNFL measurements were included. sNFL was lg-transformed (LgNfl). Participants were included whose LgNfl was higher than 1.48 pg/mL or who were diagnosed with DM. All-cause mortality was the primary outcome obtained through linkage to registries.

RESULTS

During a median follow-up of 6.1years, 85 participants died. Incidence rates (per 1000 person-years [95% CI]) of all-cause mortality were 27.78 (19.98∼35.58) in adults with LgNfl greater than 1.48 pg/mL and DM, 9.01 (1.99∼16.03) in adults with LgNfl greater than 1.48 pg/mL but no DM, 3.07 (1.01∼5.13) in adults with DM and LgNfl less than or equal to 1.48 pg/mL, and 2.21 (1.15∼3.27) in adults without DM and LgNfl less than or equal to 1.48 pg/mL. Significant interaction but not mediation was observed between LgNfl and DM. Compared with adults without DM and LgNfl less than or equal to 1.48 pg/mL, those with DM and LgNfl greater than 1.48 pg/mL had higher risks of all-cause mortality (hazard ratio; 95% CI, 7.06; 3.52∼14.16).

CONCLUSION

In general US adults with DM, elevated sNFLs were associated with higher all-cause mortality specifically, supporting an important role of sNFLs in predicting health outcome in individuals with DM.

Relationship between longer sleep and serum neurofilament light chain in american adults: evidence from the 2013-2014 US national health and nutrition examination survey

BACKGROUND

Sleep disturbance is linked to neurodegenerative diseases and the related brain pathophysiology. Serum neurofilament light chain (NfL) is a reliable biomarker for neurological disorders. This study examined the association between sleep characteristics and serum NfL levels in American adults.

METHODS

In this cross-sectional study, data from the 2013-2014 US National Health and Nutrition Examination Survey were utilized. Participants were categorized into short (≤ 6 h), normal (7-8 h), and long (≥ 9 h) sleep groups based on their self-reported sleep durations. Sleep duration, trouble sleeping, and diagnosed sleep disorders were queried, forming "sleep pattern (healthy, moderate, and poor)." The association between sleep characteristics and serum NfL levels was assessed using multivariate linear regression models. Stratification and sensitivity analyses were conducted to determine the stability of results.

RESULTS

Overall, 1637 participants were included; among them, 48.2% were male and 51.8% were female (mean ± SD, age: 46.9 ± 15.5 years) and 38.8% reported sleeping for ≤ 6 h, 54.4% for 7-8 h, and 6.8% for ≥ 9 h. Participants with longer sleep duration, poor sleep pattern, diagnosed sleep disorders, or trouble sleeping exhibited higher serum NfL levels. A positive correlation was found between extended sleep and elevated serum NfL levels (Adjusted β = 4.82, 95%CI: 2.2, 7.44, P < 0.001), with no significant correlation observed in the short-sleep group or those with poor sleep pattern. Stratified and sensitivity analyses confirmed the robustness of the relationship between longer sleep and elevated serum NfL levels.

CONCLUSIONS

A long sleep duration is associated with higher serum NfL levels than a normal sleep duration in American adults.

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.

NfL reliability across laboratories, stage-dependent diagnostic performance and matrix comparability in genetic FTD: a large GENFI study

BACKGROUND

Blood neurofilament light chain (NfL) is increasingly considered as a key trial biomarker in genetic frontotemporal dementia (gFTD). We aimed to facilitate the use of NfL in gFTD multicentre trials by testing its (1) reliability across labs; (2) reliability to stratify gFTD disease stages; (3) comparability between blood matrices and (4) stability across recruiting sites.

METHODS

Comparative analysis of blood NfL levels in a large gFTD cohort (GENFI) for (1)-(4), with n=344 samples (n=148 presymptomatic, n=11 converter, n=46 symptomatic subjects, with mutations in C9orf72, GRN or MAPT; and n=139 within-family controls), each measured in three different international labs by Simoa HD-1 analyzer.

RESULTS

NfL revealed an excellent consistency (intraclass correlation coefficient (ICC) 0.964) and high reliability across the three labs (maximal bias (pg/mL) in Bland-Altman analysis: 1.12±1.20). High concordance of NfL across laboratories was moreover reflected by high areas under the curve for discriminating conversion stage against the (non-converting) presymptomatic stage across all three labs. Serum and plasma NfL were largely comparable (ICC 0.967). The robustness of NfL across 13 recruiting sites was demonstrated by a linear mixed effect model.

CONCLUSIONS

Our results underline the suitability of blood NfL in gFTD multicentre trials, including cross-lab reliable stratification of the highly trial-relevant conversion stage, matrix comparability and cross-site robustness.

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.

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.

Serum neurofilament light chain and cognition decline in US elderly: A cross-sectional study

OBJECTIVE

Early identification of cognitive impairment in neurodegenerative diseases like Alzheimer's disease (AD) is crucial. Neurofilament, a potential biomarker for neurological disorders, has gained attention. Our study aims to investigate the relationship between serum neurofilament light (sNfL) levels and cognitive function in elderly individuals in the United States.

METHODS

This cross-sectional study analyzed data from participants aged 60 and above in the National Health and Nutrition Examination Survey (2013-2014). We collected sNfL levels, cognitive function tests, sociodemographic characteristics, comorbidities, and other variables. Weighted multiple linear regression models examined the relationship between ln(sNfL) and cognitive scores. Restricted cubic spline (RCS) visualization explored nonlinear relationships. The stratified analysis examined subgroups' ln(sNfL) and cognitive function association.

RESULTS

The study included 446 participants (47.73% male). Participants with ln(sNfL) levels between 2.58 and 2.81 pg/mL (second quintile) performed relatively well in cognitive tests. After adjusting for multiple factors, ln(sNfL) levels were negatively correlated with cognitive function, with adjusted β (95% CI) as follows: immediate recall test (IRT): -0.763 (-1.301 to -0.224), delayed recall test (DRT): -0.308 (-0.576 to -0.04), animal fluency test (AFT): -1.616 (-2.639 to -0.594), and digit symbol substitution test (DSST): -2.790 (-4.369 to -1.21). RCS curves showed nonlinear relationships between ln(sNfL) and DRT, AFT, with inflection points around 2.7 pg/mL. The stratified analysis revealed a negative correlation between ln(sNfL) and cognition in specific subgroups with distinct features, with an interaction between diabetes and ln(sNfL).

INTERPRETATION

Higher sNfL levels are associated with poorer cognitive function in the elderly population of the United States. sNfL shows promise as a potential biomarker for early identification of cognitive decline.

The association of serum neurofilament light chains with early symptoms related to Parkinson's disease: A cross-sectional study

Neurofilament light chains (NfL), released with neural axon injury, is considered as a potential biomarker for Parkinson's disease (PD). The relationship between NfL and PD has been studied mainly in diagnosed patients. Few large-scale studies analyze the association between NfL levels and multiple non-motor symptoms linked to early PD in the general population. Therefore, this study aims to determine the association of NfL with early symptoms of PD, and effectively respond to the development of early symptoms of PD. We examined the relationship between serum NfL and early non-motor symptoms of PD (smell dysfunction, sleep problems, cognitive function) and serum Klotho levels in the general population using data from the 2013-2014 National Health and Nutrition Examination Survey (NHANES). The relationship between serum NfL and early symptoms of PD in 1125 participants was analyzed by multiple linear regression and logistic regression models. The results showed a significant association between serum NfL and early symptoms of PD. There was a significant positive correlation between NfL and smell dysfunction, short sleep and long sleep. There was a significant negative correlation between NfL and Klotho levels and cognitive function test results. Further, we observed gender and age differences in the association of NfL with early symptoms of PD. Our study demonstrate that elevated serum NfL levels are positively associated with an increased risk of early PD-related symptoms, suggesting that serum NfL can be a promising biomarker for early PD.

Agreement Between Published Reference Resources for Neurofilament Light Chain Levels in People With Multiple Sclerosis

OBJECTIVES

To examine the agreement between published reference resources for neurofilament light chain (NfL) applied to a large population of people with multiple sclerosis (MS).

METHODS

Six published reference resources were used to classify NfL in participants in the Multiple Sclerosis Partners Advancing Technology and Health Solutions (MS PATHS) network as elevated or normal and to derive age-specific NfL Z-scores. NfL values were classified as elevated if they exceeded the >95th percentile (i.e., Z-score >1.645) of the age-specific reference range. Furthermore, age-specific NfL Z-scores could be derived for 4 of 6 reference resources.

RESULTS

NfL measurements were assessed from 12,855 visits of 6,687 people with MS (median 2 samples per individual [range 1-7]). The mean ± SD age was 47.1 ± 11.7 years, 72.1% of participants were female, disease duration was 15.0 ± 10.6 years, body mass index was 28.6 ± 6.9 kg/m2, and serum NfL was 12.87 ± 12.86 pg/mL. Depending on the selection of the reference resource, the proportion of NfL measurements classified as elevated varied from 3.7% to 30.9%. The kappa coefficient across the 6 reference resources used was 0.576 (95% CI 0.571-0.580) indicating moderate agreement. Spearman correlations between Z-scores derived from the various reference resources exceeded 0.90; however, concordance coefficients were lower, ranging from 0.72 to 0.89.

DISCUSSION

Interpretation of blood NfL values may vary markedly depending on the selection of the reference resource. Borderline elevated values should be interpreted with caution, and future studies should focus on standardizing NfL measurement and reporting across laboratories/platforms, better characterizing the effects of confounding/influencing factors, and defining the performance of NfL (including as part of multimodal predictive algorithms) for prediction of disease-specific outcomes.

Elevated Serum Neurofilament Light Chain Levels Are Associated With All-Cause Mortality: Evidence From National Health and Nutrition Examination Survey

BACKGROUND

Several studies have reported the association between blood neurofilament light chain (NfL) levels and all-cause mortality. However, the generalizability of these findings in general adults remains unclear. The study aimed to examine the association between serum NfL and all-cause mortality in a nationally representative population.

METHODS

Longitudinal data were obtained from 2 071 participants aged 20-75 years in the National Health and Nutrition Examination Survey 2013-14 cycle. Serum NfL levels were measured by using a novel, high-throughput acridinium-ester immunoassay. Kaplan-Meier curves, multivariate Cox regression analysis, and restricted cubic spline regression were employed to investigate the association between serum NfL and all-cause mortality.

RESULTS

Over a median follow-up of 73 (interquartile range = 12) months, 85 (3.50%) participants died. After adjustment for sociodemographic characteristics, lifestyle variables, comorbidity, body mass index, and estimated glomerular filtration rate, elevated serum NfL levels were still significantly associated with a higher risk of all-cause mortality (hazard ratio = 2.45, 95% confidence interval = 1.89-3.18 for per lnNfL increase) in a linear manner.

CONCLUSIONS

Our findings suggest that circulating levels of NfL may serve as a biomarker of mortality risk in a nationally representative population.

Quantitation of neurofilament light chain protein in serum and cerebrospinal fluid from patients with multiple sclerosis using the MSD R-PLEX NfL assay

OBJECTIVES

Neurofilament light (NfL) chain is a marker of neuroaxonal damage in various neurological diseases. Here we quantitated NfL levels in the cerebrospinal fluid (CSF) and serum from patients with multiple sclerosis (MS) and controls, using the R-PLEX NfL assay, which employs advanced Meso Scale Discovery® (MSD) electrochemiluminescence (ECL)-based detection technology.

METHODS

NfL was quantitated in samples from 116 individuals from two sites (Ottawa Hospital Research Institute and Mayo Clinic), consisting of patients with MS (n=71) and age- and sex-matched inflammatory neurological controls (n=13) and non-inflammatory controls (n=32). Correlation of NfL levels between CSF and serum was assessed in paired samples in a subset of MS patients and controls (n=61). Additionally, we assessed the correlation between NfL levels obtained with MSD's R-PLEX® and Quanterix's single molecule array (Simoa®) assays in CSF and serum (n=32).

RESULTS

Using the R-PLEX, NfL was quantitated in 99% of the samples tested, and showed a broad range in the CSF (82-500,000 ng/L) and serum (8.84-2,014 ng/L). Nf-L levels in both biofluids correlated strongly (r=0.81, p<0.0001). Lastly, Nf-L measured by MSD's R-PLEX and Quanterix's Simoa assays were highly correlated for both biofluids (CSF: r=0.94, p<0.0001; serum: r=0.95, p<0.0001).

CONCLUSIONS

We show that MSD's R-PLEX NfL assay can reliably quantitate levels of NfL in the CSF and serum from patients with MS and controls, where levels correlate strongly with Simoa.

Assessing the commutability of candidate reference materials for the harmonization of neurofilament light measurements in blood

OBJECTIVES

Neurofilament light chain (NfL) concentration in blood is a biomarker of neuro-axonal injury in the nervous system and there now exist several assays with high enough sensitivity to measure NfL in serum and plasma. There is a need for harmonization with the goal of creating a certified reference material (CRM) for NfL and an early step in such an effort is to determine the best matrix for the CRM. This is done in a commutability study and here the results of the first one for NfL in blood is presented.

METHODS

Forty paired individual serum and plasma samples were analyzed for NfL on four different analytical platforms. Neat and differently spiked serum and plasma were evaluated for their suitability as a CRM using the difference in bias approach.

RESULTS

The correlation between the different platforms with regards to measured NfL concentrations were very high (Spearman's ρ≥0.96). Samples spiked with cerebrospinal fluid (CSF) showed higher commutability compared to samples spiked with recombinant human NfL protein and serum seems to be a better choice than plasma as the matrix for a CRM.

CONCLUSIONS

The results from this first commutability study on NfL in serum/plasma showed that it is feasible to create a CRM for NfL in blood and that spiking should be done using CSF rather than with recombinant human NfL protein.

Validity of serum neurofilament light chain as a prognostic biomarker of disease activity in multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating and neuroinflammatory disease of the human central nervous system with complex pathoetiology, heterogeneous presentations and an unpredictable course of disease progression. There remains an urgent need to identify and validate a biomarker that can reliably predict the initiation and progression of MS as well as identify patient responses to disease-modifying treatments/therapies (DMTs). Studies exploring biomarkers in MS and other neurodegenerative diseases currently focus mainly on cerebrospinal fluid (CSF) analyses, which are invasive and impractical to perform on a repeated basis. Recent studies, replacing CSF with peripheral blood samples, have revealed that the elevation of serum neurofilament light chain (sNfL) in the clinical stages of MS is, potentially, an ideal prognostic biomarker for predicting disease progression and for possibly guiding treatment decisions. However, there are unresolved factors (the definition of abnormal values of sNfL concentration, the standardisation of measurement and the amount of change in sNfL concentration that is significant) that are preventing its use as a biomarker in routine clinical practice for MS. This updated review critiques these recent findings and highlights areas for focussed work to facilitate the use of sNfL as a prognostic biomarker in MS management.

Neurofilament light chain as neuronal injury marker - what is needed to facilitate implementation in clinical laboratory practice?

Neurobiomarkers have attracted significant attention over the last ten years. One promising biomarker is the neurofilament light chain protein (NfL). Since the introduction of ultrasensitive assays, NfL has been developed into a widely used axonal damage marker of relevance to the diagnosis, prognostication, follow-up, and treatment monitoring of a range of neurological disorders, including multiple sclerosis, amyotrophic lateral sclerosis, and Alzheimer's disease. The marker is increasingly used clinically, as well as in clinical trials. Even if we have validated precise, sensitive, and specific assays for NfL quantification in both cerebrospinal fluid and blood, there are analytical, as well as pre- and post-analytical aspects of the total NfL testing process, including biomarker interpretation, to consider. Although the biomarker is already in use in specialised clinical laboratory settings, a more general use requires some further work. In this review, we provide brief basic information and opinions on NfL as a biomarker of axonal injury in neurological diseases and pinpoint additional work needed to facilitate biomarker implementation in clinical practice.

Associations of sNfL with clinico-radiological measures in a large MS population

OBJECTIVE

Evaluation of serum neurofilament light chain (sNfL), measured using high-throughput assays on widely accessible platforms in large, real-world MS populations, is a critical step for sNfL to be utilized in clinical practice.

METHODS

Multiple Sclerosis Partners Advancing Technology and Health Solutions (MS PATHS) is a network of healthcare institutions in the United States and Europe collecting standardized clinical/imaging data and biospecimens during routine clinic visits. sNfL was measured in 6974 MS and 201 healthy control (HC) participants, using a high-throughput, scalable immunoassay.

RESULTS

Elevated sNfL levels for age (sNfL-E) were found in 1238 MS participants (17.8%). Factors associated with sNfL-E included male sex, younger age, progressive disease subtype, diabetes mellitus, impaired renal function, and active smoking. Higher body mass index (BMI) was associated with lower odds of elevated sNfL. Active treatment with disease-modifying therapy was associated with lower odds of sNfL-E. MS participants with sNfL-E exhibited worse neurological function (patient-reported disability, walking speed, manual dexterity, and cognitive processing speed), lower brain parenchymal fraction, and higher T2 lesion volume. Longitudinal analyses revealed accelerated short-term rates of whole brain atrophy in sNfL-E participants and higher odds of new T2 lesion development, although both MS participants with or without sNfL-E exhibited faster rates of whole brain atrophy compared to HC. Findings were consistent in analyses examining age-normative sNfL Z-scores as a continuous variable.

INTERPRETATION

Elevated sNfL is associated with clinical disability, inflammatory disease activity, and whole brain atrophy in MS, but interpretation needs to account for comorbidities including impaired renal function, diabetes, and smoking.

Ella versus Simoa Serum Neurofilament Assessment to Monitor Treatment Response in Highly Active Multiple Sclerosis Patients

The measurement of serum neurofilament light chain (sNfL) is of growing importance in the field of neurology. In the management of multiple sclerosis, it can serve as a useful marker to assess disease activity and treatment response. This paper compares two available methods, namely the Single Molecule Array (Simoa) and the Ella microfluid platform, to measure longitudinal sNfL levels of 42 highly active multiple sclerosis patients treated with alemtuzumab over a period of 36 months. In order to assess the methods agreement, Bland-Altman plots and Passing-Bablok regression were analyzed. Here, we show that despite the fact that Ella measures around 24% higher values than Simoa, both are equally suitable for longitudinal sNfL monitoring.