Contributors to Serum NfL Levels in People without Neurologic Disease

Age-corrected neurofilament light chain ratio decreases but does not predict relapse in highly active multiple sclerosis patients initiating natalizumab treatment

BACKGROUND

Neurofilament light chain (NFL) is a biomarker for monitoring disease activity and treatment response in multiple sclerosis (MS). However, while most agree that NFL levels predict disease activity and worsening, the predictive value of NFL on future relapse risk remains uncertain.

OBJECTIVE

The primary aim was to evaluate the predictive value of age-corrected serum NFL (sNFL) ratio on relapse risk in highly active relapsing-remitting MS patients (RRMS) treated with natalizumab. A secondary aim was to investigate the predictive value of sNFL ratios for MRI activity.

METHODS

From January 1, 2006, to December 31, 2010, 355 patients initiated natalizumab treatment at the Danish Multiple Sclerosis Center. 305 patients were anti-natalizumab antibodies negative and had at least one blood sample available for sNFL analysis using single molecule array analysis at baseline, three, six, or 12 months. The patients were either treatment-naïve (n = 8), switching from interferon-β or glatiramer acetate (n = 253), or switching from mitoxantrone (n = 44). An age-corrected ratio was calculated for sNFL. Time to first relapse was calculated from baseline and after re-baseline at 90 days. Data were collected from baseline until the two-year follow-up or end of treatment and included disease duration, expanded disability status scale, previous treatments, relapses 12 months prior to natalizumab initiation, smoking intensity, body mass index, and body weight. In addition, the patients underwent annual MRI of the brain.

RESULTS

The sNFL ratio was increased in 173 of 287 samples (60.3 %) at baseline, in 119 of 246 samples (48.8 %) at month three, in 109 of 287 samples (38.0 %) at month six, and in 82 of 270 samples (30.4 %) at month 12. The sNFL ratio continuously declined over 12 months with significant decreases for every measuring timepoint: baseline vs. three months p = 3.0 × 10-6; three months vs. six months p = 3.2 × 10-5; six months vs. 12 months p = 0.002. Univariate Cox regression analysis showed that time to first relapse from 1) natalizumab initiation and from 2) re-baseline was associated with the number of relapses in the previous 12 months (hazard ratio 1.31 per relapse, 95 % CI = 1.2-1.5, p = 2.0 × 10-6; and 1.21 per relapse, 95 % CI = 1.1-1.4, p = 0.002, respectively). sNFL ratio at re-baseline was negatively associated with relapse risk (hazard ratio 0.82 per unit; 95 % CI = 0.7-1.0; p = 0.049). A multivariable Cox regression analysis of relapse risk from re-baseline showed that the number of relapses in the 12 months prior to natalizumab treatment (hazard ratio 1.29; 95 % CI = 1.1-1.5; p = 6.0 × 10-4) and smoking (hazard ratio 1.51 per 20 cigarettes per day; 95 % CI = 1.0-2.2; p = 0.030) were associated with increased risk of relapse; sNFL ratio was associated with a lower risk of relapse (hazard ratio = 0.736 per unit; 95 % CI = 0.6-0.9 p = 0.007). In univariate logistic regression analyses, the sNFL ratio at 12 months and values above the 75th and the 90th percentile predicted MRI activity in the following year (odds ratio [OR] = 2.0, 95 % CI = 1.2-3.6, p = 0.012; OR = 2.2, 95 % CI = 1.2-4.1, p = 0.014; and OR = 2.8, 95 % CI = 1.1-6.7, p = 0.026).

CONCLUSION

In this highly active RRMS cohort, high sNFL ratios reflected previous relapse activity and decreased after initiation of treatment but were not associated with increased relapse risk in the following two years. Pre-treatment relapses and smoking on treatment were predictors of relapse risk after re-baselining at 90 days. MRI activity in year two was predicted by sNFL ratios at month 12.

Serum neurofilament light chain levels are associated with depression among US adults: a cross-sectional analysis among US adults, 2013-2014

BACKGROUND

Serum neurofilament light chain (sNfL) has been identified as a biomarker for neurologic diseases. However, sNfL remains unknown to be responsible for depression.

AIMS

The aim of this research was to explore the relationship between sNfL levels and depression in US adults.

METHODS

In this cross-sectional survey of the general population, we investigated representative data involving 10,175 participants from the 2013-2014 cycle of the National Health and Nutrition Examination Survey (NHANES). Depression was diagnosed using the Patient Health Questionnaire-9 (PHQ-9). The effect of related factors on depression was analyzed by conducting a univariate analysis. Stratified analysis was utilized to detect the stability and sensitivity of the relationship. After adjusting for race, education, marital status, smoking status, body mass index (BMI), sleep duration, income, and a history of hypertension, sedentary behavior and stroke, multivariable linear regression was performed to demonstrate the correlation between sNfL and depression.

RESULTS

A total of 1301 individuals between the ages of 20 and 75 were involved in this investigation, of which 108 (8.3%) were diagnosed with depression. A significant positive correlation between sNfL and depression among adults in the US was observed by conducting univariable analyses. After adjusting for confounding factors, the multivariate analyses indicated that elevated sNfL levels might play a pivotal role in the development of depression (odds ratio (OR) = 3.0; 95% confidence interval (CI): (1.5, 6.1), P = 0.002).

CONCLUSION

These results indicated that sNfL is closely linked to depression in a nationally representative individual. However, further studies are needed to confirm the biological mechanism as well as the clinical implications of sNfL and depression.

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.

NfL concentration in CSF is a quantitative marker of the rate of neurodegeneration in aging and Huntington's disease: a semi-mechanistic model-based analysis

The concentrations of neurofilament light chain (NfL) in cerebrospinal fluid (CSF) and plasma have become key biomarkers of many neurodegenerative diseases, including Huntington's Disease (HD). However, the relationship between the dynamics of NfL concentrations in CSF and the time-course of neurodegeneration (whole brain atrophy) has not yet been described in a quantitative and mechanistic manner. Here, we present a novel semi-mechanistic model, which postulates that the amount of NfL entering the CSF corresponds to the amount of NfL released from damaged neurons, whose degeneration results in a decrease in brain volume. In mathematical terms, the model expresses the NfL concentration in CSF in terms of the NfL concentration in brain tissue, the rate of change of whole brain volume and the CSF flow rate. To test our model, we used a non-linear mixed effects approach to analyze NfL and brain volume data from the HD-CSF study, a 24-month prospective study of individuals with premanifest HD, manifest HD and healthy controls. The time-course of whole brain volume, obtained from MRI, was represented empirically by a 2nd order polynomial, from which its rate of change was computed. CSF flow rates in healthy and HD populations were taken from recent literature data. By estimating the NfL concentration in brain tissue, the model successfully described the time-course of the NfL concentration in CSF in both HD subjects and healthy controls. Furthermore, the model-derived estimate of NfL concentration in brain agreed well with recent direct experimental measurements. The consistency of our model with the NfL and brain volume data suggests that the NfL concentration in CSF reflects the rate, rather than the extent, of neurodegeneration and that the increase in NfL concentration over time is a measure of the accelerating rate of neurodegeneration associated with aging and HD. For HD subjects, the degree of acceleration was found to increase markedly with the number of CAG repeats on their HTT gene. The application of our semi-mechanistic NfL model to other neurodegenerative diseases is discussed.

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.

Association of Dietary Retinol Intake and Serum Neurofilament Light Chain Levels: Results from NHANES 2013-2014

BACKGROUND

There is increasing evidence suggesting that serum neurofilament light chain (sNfL) levels can be used as biomarkers for axonal injury. Retinol is recognized for its significant involvement in nervous system function, but the precise connection between dietary retinol and sNfL levels remains uncertain.

OBJECTIVE

Our objective was to investigate the relationship between dietary retinol intake and sNfL, and to find an optimal retinol intake level for neurological health.

METHODS

In the National Health and Nutrition Examination Survey (NHANES), conducted from 2013 to 2014, a cohort of 1684 participants who met the criteria were selected for the study. sNfL levels were measured from stored serum samples using a novel high-throughput immunoassay platform from Siemens Healthineers. Assessment of dietary retinol intake was performed by a uniformly trained interviewer through a 24 h dietary recall method. A generalized linear model was evaluated to assess the correlation between dietary retinol intake and sNfL concentrations. Furthermore, the nonlinear association between the two is further explored using restricted cubic spline (RCS) analysis.

RESULTS

Upon adjusting for potential confounders, a 10% increase in dietary retinol intake was associated with a 3.47% increase in sNfL levels (95% CI: 0.54%, 6.49%) across all participants. This relationship was more pronounced in specific subgroups, including those under 60 years of age, non-obese, impaired estimated glomerular filtration rate (eGFR), and non-diabetic. In subgroup analysis, among those younger than 60 years of age (percent change: 3.80%; 95% CI: 0.43%, 7.28%), changes were found in non-obese participants (percent change: 6.28%; 95% CI: 2.66%, 10.02%), those with impaired eGFR (percent change: 6.90%; 95% CI: 1.44%, 12.65%), and non-diabetic patients (percentage change: 4.17%; 95% CI: 1.08%, 7.36%). RCS analysis showed a linear relationship between dietary retinol intake and sNfL levels. Furthermore, the positive correlation between the two was more significant after the inflection point, according to piecewise linear analysis.

CONCLUSION

This current investigation uncovered a J-shaped relationship between dietary retinol and sNfL levels, suggesting that axonal damage can occur when dietary retinol intake increases more than a specific threshold. These findings need to be further confirmed in future prospective studies to determine the precise intake level that may trigger axonal injury.

APOE ε4 carrier status modifies plasma p-tau181 concentrations in cognitively healthy super-seniors

INTRODUCTION

This study investigates the effect of apolipoprotein E (APOE) genotype on neurology plasma biomarkers in cognitively healthy Super-Seniors.

METHODS

Three hundred seventy plasma specimens from Super-Senior participants ≥ 85 years old, who have never been diagnosed with dementia, cancer, diabetes, cardiovascular, or major pulmonary disease, were analyzed on the Quanterix Simoa HD-X analyzer using commercial Neurology 4-plex E and phosphorylated tau (p-tau)181 assays.

RESULTS

Eighty (22%) participants were APOE ε4 carriers and 290 (73%) were non-carriers. No significant differences were found between APOE ε4 carriers and non-carriers regarding age, sex, or Mini-Mental State Examination scores. In APOE ε4 carriers, plasma amyloid beta 42/40 was lower and p-tau181 and glial fibrillary acidic protein were higher compared to non-APOE ε4 carriers. After adjusting for demographic variables, p-tau181 was the only biomarker to remain significantly associated with APOE ε4 carrier status.

DISCUSSION

APOE ε4 genotype modifies plasma p-tau181 concentration in seniors resilient to age-related clinical disease, suggesting that some Super-Seniors may have Alzheimer's disease pathology without progressing to cognitive decline.

HIGHLIGHTS

Healthy seniors enable identification of associations that may be masked by disease. Plasma phosphorylated tau (p-tau)181 concentrations associate with apolipoprotein E (APOE) ε4 carriership in healthy seniors. APOE should be accounted for when interpreting p-tau181, regardless of disease.

Serum neurofilament light chain as a prognostic marker of all-cause mortality in a national sample of US adults

Neurofilament light chain (NfL) is a neuron-specific structural protein released into the extracellular space, including body fluids, upon neuroaxonal damage. Despite evidence of a link in neurological disorders, few studies have examined the association of serum NfL with mortality in population-based studies. Data from the National Health and Nutrition Survey were utilized including 2,071 Non-Hispanic White, Non-Hispanic Black and Hispanic adult participants and adult participants of other ethnic groups (20-85 years) with serum NfL measurements who were followed for ≤ 6 years till 2019. We tested the association of serum NfL with mortality in the overall population and stratified by sex with the addition of potential interactive and mediating effects of cardio-metabolic risk factors and nutritional biomarkers. Elevated serum NfL levels (above median group) were associated with mortality risk compared to the below median NfL group in the overall sample (P = 0.010), with trends observed within each sex group (P < 0.10). When examining Loge NfL as a continuum, one standard deviation of Loge NfL was associated with an increased mortality risk (HR = 1.88, 95% CI 1.60-2.20, P < 0.001) in the reduced model adjusted for age, sex, race, and poverty income ratio; a finding only slightly attenuated with the adjustment of lifestyle and health-related factors. Four-way decomposition indicated that there was, among others, mediated interaction between NfL and HbA1c and a pure inconsistent mediation with 25(OH)D3 in predicting all-cause mortality, in models adjusted for all other covariates. Furthermore, urinary albumin-to-creatinine ratio interacted synergistically with NfL in relation to mortality risk both on the additive and multiplicative scales. These data indicate that elevated serum NfL levels were associated with all-cause mortality in a nationally representative sample of US adults.

Association between volatile organic compounds and serum neurofilament light chain in US adults

OBJECTIVE

This study aimed to investigate the associations between exposure to blood volatile organic compounds (VOCs) and the level of serum neurofilament light chain (NfL) in adults.

METHODS

We analyzed data from the 2013-2014 National Health and Nutrition Examination Survey (NHANES), including 2008 participants aged 20 to 75 years old. Multiple linear regression models were used to examine the associations between 28 VOCs and NfL after adjusting for multiple potential confounders. Restricted cubic spline (RCS) was used to examine the potential non-linear associations.

RESULTS

The linear regression models showed that higher levels of 2,5-dimethylfuran (β = 0.042, 95 % confidence interval [CI]: 0.001, 0.096), ethyl acetate (β = 0.118, 95 % CI = 0.008, 0.304), and m-/p-xylene (β = 0.043, 95%CI = 0.012, 0.074) were associated with higher NfL levels. These estimates were largely consistent after adjusting for multiple confounders.

CONCLUSION

The findings of our study suggest a potential association between certain volatile organic compounds (2,5-dimethylfuran, ethyl acetate, and m-/p-xylene) and blood NfL levels, implying that they may have a role in revealing neurodegeneration and influencing neurological health.

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.

Body fluid markers for multiple sclerosis and differential diagnosis from atypical demyelinating disorders

INTRODUCTION

Body fluid markers could be helpful to predict the conversion into clinically definite multiple sclerosis (MS) in people with a first demyelinating event of the central nervous system (CNS). Consequently, biomarkers such as oligoclonal bands, which are integrated in the current MS diagnostic criteria, could assist early MS diagnosis.

AREAS COVERED

This review examines existing knowledge on a broad spectrum of body fluid markers in people with a first CNS demyelinating event, explores their potential to predict conversion to MS, to assess MS disease activity, as well as their utility to differentiate MS from atypical demyelinating disorders such as neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein associated disease.

EXPERT OPINION

This field of research has shown a dramatic increase of evidence, especially in the last decade. Some biomarkers are already established in clinical routine (e.g. oligoclonal bands) while others are currently implemented (e.g. kappa free light chains) or considered as breakthroughs (e.g. neurofilament light). Determination of biomarkers poses challenges for continuous monitoring, especially if exclusively detectable in cerebrospinal fluid. A handful of biomarkers are measurable in blood which holds a significant potential.

Neurofilament Light Chains in Systemic Amyloidosis: A Systematic Review

Peripheral and autonomic neuropathy are common disease manifestations in systemic amyloidosis. The neurofilament light chain (NfL), a neuron-specific biomarker, is released into the blood and cerebrospinal fluid after neuronal damage. There is a need for an early and sensitive blood biomarker for polyneuropathy, and this systematic review provides an overview on the value of NfL in the early detection of neuropathy, central nervous system involvement, the monitoring of neuropathy progression, and treatment effects in systemic amyloidosis. A literature search in PubMed, Embase, and Web of Science was performed on 14 February 2024 for studies investigating NfL levels in patients with systemic amyloidosis and transthyretin gene-variant (TTRv) carriers. Only studies containing original data were included. Included were thirteen full-text articles and five abstracts describing 1604 participants: 298 controls and 1306 TTRv carriers or patients with or without polyneuropathy. Patients with polyneuropathy demonstrated higher NfL levels compared to healthy controls and asymptomatic carriers. Disease onset was marked by rising NfL levels. Following the initiation of transthyretin gene-silencer treatment, NfL levels decreased and remained stable over an extended period. NfL is not an outcome biomarker, but an early and sensitive disease-process biomarker for neuropathy in systemic amyloidosis. Therefore, NfL has the potential to be used for the early detection of neuropathy, monitoring treatment effects, and monitoring disease progression in patients with systemic amyloidosis.

Association between urinary glyphosate levels and serum neurofilament light chain in a representative sample of US adults: NHANES 2013-2014

BACKGROUND

Glyphosate, the herbicide with the highest global usage, has been found to have links to neurological impairment in some occupational studies. Neurofilament light chain (NfL) is a protein that is released into the bloodstream following neuroaxonal damage and has emerged as a reliable biomarker for various neurological disorders. However, no research has investigated the potential link between glyphosate exposure and neurological damage or serum NfL levels in the general population.

OBJECTIVE

The objective of this study was to assess the possible correlation between glyphosate exposure and serum NfL levels in a population that is representative of the United States.

METHODS

We analyzed data from 597 adults (aged ≥20 years) from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) to explore the potential correlation between urinary glyphosate levels and serum NfL levels.

RESULTS

We found a significant positive association between urinary glyphosate levels and serum NfL levels (ß-coefficient = 0.110; S.E. = 0.040; P = 0.015), indicating that higher levels of glyphosate exposure may be linked to higher levels of neuroaxonal damage. Furthermore, when glyphosate levels were divided into quintiles, we observed a significant trend of increasing mean NfL concentrations with increasing quintiles of glyphosate exposure (P for trend = 0.036). Notably, the association was more pronounced in certain subgroups, including those aged ≥40 years, non-Hispanic whites, and those with a BMI between 25 and 30.

IMPACT STATEMENT

This is the first research to suggest an association between glyphosate exposure and biomarkers indicative of neurological damage in general U.S. adults. If the correlation observed is causal, it raises concerns about the potential effects of glyphosate exposure on neurological health among U.S. adults. The study is noteworthy due to its representation of American adults aged 20 and above, as well as the use of reliable and comprehensive data from the NHANES database.

Systemic inflammation relates to neuroaxonal damage associated with long-term cognitive dysfunction in COVID-19 patients

BACKGROUND AND OBJECTIVES

Cognitive deficits are increasingly recognized as a long-term sequela of severe COVID-19. The underlying processes and molecular signatures associated with these long-term neurological sequalae of COVID-19 remain largely unclear, but may be related to systemic inflammation-induced effects on the brain. We studied the systemic inflammation-brain interplay and its relation to development of long-term cognitive impairment in patients who survived severe COVID-19. Trajectories of systemic inflammation and neuroaxonal damage blood biomarkers during ICU admission were analyzed and related to long-term cognitive outcomes.

METHODS

Prospective longitudinal cohort study of patients with severe COVID-19 surviving ICU admission. During admission, blood was sampled consecutively to assess levels of inflammatory cytokines and neurofilament light chain (NfL) using an ultrasensitive multiplex Luminex assay and single molecule array technique (Simoa). Cognitive functioning was evaluated using a comprehensive neuropsychological assessment six months after ICU-discharge.

RESULTS

Ninety-six patients (median [IQR] age 61 [55-69] years) were enrolled from March 2020 to June 2021 and divided into two cohorts: those who received no COVID-19-related immunotherapy (n = 28) and those treated with either dexamethasone or dexamethasone and tocilizumab (n = 68). Plasma NfL concentrations increased in 95 % of patients during their ICU stay, from median [IQR] 23 [18-38] pg/mL at admission to 250 [160-271] pg/mL after 28 days, p < 0.001. Besides age, glomerular filtration rate, immunomodulatory treatment, and C-reactive protein, more specific markers of systemic inflammation at day 14 (i.e., interleukin (IL)-8, tumour necrosis factor, and IL-1 receptor antagonist) were significant predictors of blood NfL levels at day 14 of ICU admission (R2 = 44 %, p < 0.001), illustrating the association between sustained systemic inflammation and neuroaxonal damage. Twenty-six patients (27 %) exhibited cognitive impairment six months after discharge from the ICU. NfL concentrations showed a more pronounced increase in patients that developed cognitive impairment (p = 0.03). Higher NfL predicted poorer outcome in information processing speed (Trail Making Test A, r = -0.26, p = 0.01; Letter Digit Substitution Test, r = -0.24, p = 0.02).

DISCUSSION

Prolonged systemic inflammation in critically ill COVID-19 patients is related to neuroaxonal damage and subsequent long-term cognitive impairment. Moreover, our findings suggest that plasma NfL concentrations during ICU stay may possess prognostic value in predicting future long-term cognitive impairment in patients that survived severe COVID-19.

Guidance for use of neurofilament light chain as a cerebrospinal fluid and blood biomarker in multiple sclerosis management

Neurofilament light chain (NfL) is a long-awaited blood biomarker that can provide clinically useful information about prognosis and therapeutic efficacy in multiple sclerosis (MS). There is now substantial evidence for this biomarker to be used alongside magnetic resonance imaging (MRI) and clinical measures of disease progression as a decision-making tool for the management of patients with MS. Serum NfL (sNfL) has certain advantages over traditional measures of MS disease progression such as MRI because it is relatively noninvasive, inexpensive, and can be repeated frequently to monitor activity and treatment efficacy. sNfL levels can be monitored regularly in patients with MS to determine change from baseline and predict subclinical disease activity, relapse risk, and the development of gadolinium-enhancing (Gd+) lesions. sNfL does not replace MRI, which provides information related to spatial localisation and lesion stage. Laboratory platforms are starting to be made available for clinical application of sNfL in several countries. Further work is needed to resolve issues around comparisons across testing platforms (absolute values) and normalisation (reference ranges) in order to guide interpretation of the results.

Correlation analysis between smoke exposure and serum neurofilament light chain in adults: a cross-sectional study

BACKGROUND

Smoke exposure is a prevalent and well-documented risk factor for various diseases across different organ systems. Serum neurofilament light chain (sNfL) has emerged as a promising biomarker for a multitude of nervous system disorders. However, there is a notable paucity of research exploring the associations between smoke exposure and sNfL levels.

METHODS

We conducted a comprehensive analysis of the National Health and Nutrition Examination Survey (NHANES) cross-sectional data spanning the years 2013 to 2014. Serum cotinine levels were classified into the following three groups: < 0.05, 0.05-2.99, and ≥ 3 ng/ml. Multiple linear regression models were employed to assess the relationships between serum cotinine levels and sNfL levels. Additionally, we utilized restricted cubic spline analyses to elucidate the potential nonlinear relationship between serum cotinine and sNfL levels.

RESULTS

A total of 2053 participants were included in our present research. Among these individuals, the mean age was 47.04 ± 15.32 years, and males accounted for 48.2% of the total study population. After adjusting the full model, serum cotinine was positively correlated with sNfl in the second group (β = 0.08, 95%CI 0.01-0.15) and in the highest concentration of serum cotinine (β = 0.10, 95%CI 0.01-0.19) compared to the group with the lowest serum cotinine concentrations. Current smokers, in comparison to non-smokers, exhibited a trend toward elevated sNfL levels (β = 0.07, 95%CI 0.01-0.13). Furthermore, subgroup analyses revealed interactions between serum cotinine levels and different age groups (P for interaction = 0.001) and gender stratification (P for interaction = 0.015) on sNfL levels.

CONCLUSION

The study suggested that serum cotinine was significantly and positively associated with sNfl levels in adult participants. Furthermore, current smokers tend to exhibit elevated sNfL levels. This research sheds light on the potential implications of smoke exposure on neurological function impairment and underscores the importance of further exploration in this area.

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.

Plasma neurofilament light in behavioural variant frontotemporal dementia compared to mood and psychotic disorders

OBJECTIVE

Blood biomarkers of neuronal injury such as neurofilament light (NfL) show promise to improve diagnosis of neurodegenerative disorders and distinguish neurodegenerative from primary psychiatric disorders (PPD). This study investigated the diagnostic utility of plasma NfL to differentiate behavioural variant frontotemporal dementia (bvFTD, a neurodegenerative disorder commonly misdiagnosed initially as PPD), from PPD, and performance of large normative/reference data sets and models.

METHODS

Plasma NfL was analysed in major depressive disorder (MDD, n = 42), bipolar affective disorder (BPAD, n = 121), treatment-resistant schizophrenia (TRS, n = 82), bvFTD (n = 22), and compared to the reference cohort (Control Group 2, n = 1926, using GAMLSS modelling), and age-matched controls (Control Group 1, n = 96, using general linear models).

RESULTS

Large differences were seen between bvFTD (mean NfL 34.9 pg/mL) and all PPDs and controls (all < 11 pg/mL). NfL distinguished bvFTD from PPD with high accuracy, sensitivity (86%), and specificity (88%). GAMLSS models using reference Control Group 2 facilitated precision interpretation of individual levels, while performing equally to or outperforming models using local controls. Slightly higher NfL levels were found in BPAD, compared to controls and TRS.

CONCLUSIONS

This study adds further evidence on the diagnostic utility of NfL to distinguish bvFTD from PPD of high clinical relevance to a bvFTD differential diagnosis, and includes the largest cohort of BPAD to date. Using large reference cohorts, GAMLSS modelling and the interactive Internet-based application we developed, may have important implications for future research and clinical translation. Studies are underway investigating utility of plasma NfL in diverse neurodegenerative and primary psychiatric conditions in real-world clinical settings.

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.

Age specific reference intervals for plasma biomarkers of neurodegeneration and neurotrauma in a Canadian population

INTRODUCTION

In this study, we aimed to create reference intervals (RI) using a large Canadian population-based cohort, for plasma protein biomarkers with potential utility to screen, diagnosis, prognosticate and manage a variety of neurological diseases and disorders. RIs were generated for: the ratio of amyloid beta 42 over 40 (Aβ42/40), phosphorylated tau-181 (p-tau-181), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP).

METHODS

900 plasma specimens from male and female participants aged 3-79 years old were obtained from the Statistics Canada Biobank, which holds specimens from the Canadian Health Measures Survey. Analysis of Aβ42/40, p-tau-181, NfL and GFAP was performed on the Quanterix Simoa HD-X analyzer using the Neurology 4-plex E and p-tau-181 assays. Discrete RIs were produced according to Clinical Laboratory Standards Institute guidelines (EP28-A3c). Continuous RIs were created using quantile regression.

RESULTS

For discrete RIs, significant age partitions were determined for each biomarker. No significant sex partitions were found. The following ranges and age partitions were determined: Aβ42/40: 3-<55y = 0.053-0.098, 55-<80y = 0.040-0.090; p-tau-181: 3-<12y = 1.4-5.6 pg/ml, 12-<60y = 0.8-3.1 pg/ml, 60-<80y = 0.9-4.0 pg/ml; NfL: 3-<40y = 2.6-11.3 pg/ml, 40-<60y = 4.6-17.7 pg/ml, 60-<80y = 8.1-47.1 pg/ml; GFAP; 3-<10y = 47.0-226 pg/ml, 10-<60y = 21.2-91.9 pg/ml, 60-<80y = 40.7-228 pg/ml. Continuous RIs produced smooth centile curves across the age range, from which point estimates for each year of age were calculated.

CONCLUSIONS

Discrete and continuous RIs for neurological plasma biomarkers will help refine normative cut-offs across the lifespan and improve the precision of interpretating biomarker levels. Continuous RIs are recommended for use in age groups, such as pediatrics and older adults, that experience rapid concentration changes by age.

Neurofilament light chain: serum reference intervals in Danish children aged 0-17 years

Elevated levels of neurofilament light chain (NfL) in the blood is an unspecific biomarker for damage to neuronal axons. The measurement of NfL levels in the blood can provide useful information for monitoring and prognostication of various neurological disorders in children, but a reference interval (RI) is needed before the clinical implementation of the biomarker. We aimed to establish a RI for children aged 0-17 years. Serum samples from 292 healthy reference subjects aged 0.4-17.9 years were analysed by a single-molecule array (Simoa®) established for routine clinical use. Non-parametric quantile regression was used to model a continuous RI, and a traditional age-partitioned non-parametric RI was established according to Clinical and Laboratory Standard Institute (CLSI) guideline C28-A3. Furthermore, we investigated the effect of hemolysis on assay performance. The traditional age-partitioned non-parametric RI for the age group <3 years was 3.5-16.6 ng/L and 2.1-13.9 ng/L in the age group ≥3 years, respectively. The continuous RI showed an age-dependent decrease in median NfL levels in the first three years of life which was also evident in the age-partitioning of the traditional RI. We found no difference between sexes and no impact of hemolysis on the NfL test results. This study establishes a pediatric RI for serum NfL and lays the groundwork for its future use in clinical practice.

Serum neurofilament light chain reference database for individual application in paediatric care: a retrospective modelling and validation study

BACKGROUND

Neurological conditions represent an important driver of paediatric disability burden worldwide. Measurement of serum neurofilament light chain (sNfL) concentrations, a specific marker of neuroaxonal injury, has the potential to contribute to the management of children with such conditions. In this context, the European Medicines Agency recently declared age-adjusted reference values for sNfL a top research priority. We aimed to establish an age-adjusted sNfL reference range database in a population of healthy children and adolescents, and to validate this database in paediatric patients with neurological conditions to affirm its clinical applicability.

METHODS

To generate a paediatric sNfL reference dataset, sNfL values were measured in a population of healthy children and adolescents (aged 0-22 years) from two large cohorts in Europe (the Coronavirus Antibodies in Kids from Bavaria study, Germany) and North America (a US Network of Paediatric Multiple Sclerosis Centers paediatric case-control cohort). Children with active or previous COVID-19 infection or SARS-CoV-2 antibody positivity at the time of sampling, or a history of primary systemic or neurological conditions were excluded. Linear models were used to restrospectively study the effect of age and weight on sNfL concentrations. We modelled the distribution of sNfL concentrations as a function of age-related physiological changes to derive reference percentile and Z score values via a generalised additive model for location, scale, and shape. The clinical utility of the new reference dataset was assessed in children and adolescents (aged 1-19 years) with neurological diseases (epilepsy, traumatic brain injury, bacterial CNS infections, paediatric-onset multiple sclerosis, and myelin oligodendrocyte glycoprotein antibody-associated disease) from the paediatric neuroimmunology clinic at the University of California San Francisco (San Francisco, CA, USA) and the Children's Hospital of the University of Regensburg (Regensburg, Germany).

FINDINGS

Samples from 2667 healthy children and adolescents (1336 [50·1%] girls and 1331 [49·9%] boys; median age 8·0 years [IQR 4·0-12·0]) were used to generate the reference database covering neonatal age to adolescence (target age range 0-20 years). In the healthy population, sNfL concentrations decreased with age by an estimated 6·8% per year until age 10·3 years (estimated multiplicative effect per 1 year increase 0·93 [95% CI 0·93-0·94], p<0·0001) and was mostly stable thereafter up to age 22 years (1·00 [0·52-1·94], p>0·99). Independent of age, the magnitude of the effect of weight on sNfL concentrations was marginal. Samples from 220 children with neurological conditions (134 [60·9%] girls and 86 [39·1%] boys; median age 14·7 years [IQR 10·8-16·5]) were used to validate the clinical utility of the reference Z scores. In this population, age-adjusted sNfL Z scores were higher than in the reference population of healthy children and adolescents (p<0·0001) with higher effect size metrics (Cohen's d=1·56) compared with the application of raw sNfL concentrations (d=1·28).

INTERPRETATION

The established normative sNfL values in children and adolescents provide a foundation for the clinical application of sNfL in the paediatric population. Compared with absolute sNfL values, the use of sNfL Z score was associated with higher effect size metrics and allowed for more accurate estimation of the extent of ongoing neuroaxonal damage in individual patients.

FUNDING

Swiss National Science Foundation, US National Institutes of Health, and the National Multiple Sclerosis Society.

Prediabetes is associated with a higher serum neurofilament light chain level in adolescents

Objective

Serum neurofilament light chain (sNfL) level, which is a biomarker indicative of neuroaxonal damage and cognitive impairment, has been reported in several neurological diseases. There has been a lack of studies on the association between sNfL levels and prediabetes in adolescents. This study investigated whether sNfL levels were higher in adolescents with prediabetes undergoing elective orthopedic surgery.

Methods

The sNfL level was measured in 149 adolescents aged from 12 to 18 years who underwent elective orthopedic surgery at the Hunan Children's Hospital (18 with and 131 without prediabetes). We evaluated the association between prediabetes and sNfL level after adjusting for age, sex, and triglycerides using a multivariable linear regression model.

Results

The prevalence of prediabetes in adolescents was 12.08%. Univariate logistic regression analysis showed that prediabetes was related to sNfL. In multivariate logistic regression analysis, the association between prediabetes with sNfL levels remained significant after adjustment for age, sex, and triglyceride. The relationship between the two was further visualized by a smoothed curve.

Conclusions

Prediabetes is associated with a higher sNfL. Further large-scale and prospective studies are needed to verify the clinical application of sNfL as a monitoring biomarker for adolescent prediabetes in adolescents and to evaluate the performance of sNfL in predicting the incidence of neuropathy and cognitive dysfunction in adolescents with prediabetes.

Neurofilament light chains to assess sepsis-associated encephalopathy: Are we on the track toward clinical implementation?

Sepsis is the most common cause of admission to intensive care units worldwide. Sepsis patients frequently suffer from sepsis-associated encephalopathy (SAE) reflecting acute brain dysfunction. SAE may result in increased mortality, extended length of hospital stay, and long-term cognitive dysfunction. The diagnosis of SAE is based on clinical assessments, but a valid biomarker to identify and confirm SAE and to assess SAE severity is missing. Several blood-based biomarkers indicating neuronal injury have been evaluated in sepsis and their potential role as early diagnosis and prognostic markers has been studied. Among those, the neuroaxonal injury marker neurofilament light chain (NfL) was identified to potentially serve as a prognostic biomarker for SAE and to predict long-term cognitive impairment. In this review, we summarize the current knowledge of biomarkers, especially NfL, in SAE and discuss a possible future clinical application considering existing limitations.

Prognostic performance of blood neurofilament light chain protein in hospitalized COVID-19 patients without major central nervous system manifestations: an individual participant data meta-analysis

BACKGROUND AND AIMS

To investigate the prognostic value of blood neurofilament light chain protein (NfL) levels in the acute phase of coronavirus disease 2019 (COVID-19).

METHODS

We conducted an individual participant data (IPD) meta-analysis after screening on MEDLINE and Scopus to May 23rd 2022. We included studies with hospitalized adult COVID-19 patients without major COVID-19-associated central nervous system (CNS) manifestations and with a measurement of blood NfL in the acute phase as well as data regarding at least one clinical outcome including intensive care unit (ICU) admission, need of mechanical ventilation (MV) and death. We derived the age-adjusted measures NfL Z scores and conducted mixed-effects modelling to test associations between NfL Z scores and other variables, encompassing clinical outcomes. Summary receiver operating characteristic curves (SROCs) were used to calculate the area under the curve (AUC) for blood NfL.

RESULTS

We identified 382 records, of which 7 studies were included with a total of 669 hospitalized COVID-19 cases (mean age 66.2 ± 15.0 years, 68.1% males). Median NfL Z score at admission was elevated compared to the age-corrected reference population (2.37, IQR: 1.13-3.06, referring to 99th percentile in healthy controls). NfL Z scores were significantly associated with disease duration and severity. Higher NfL Z scores were associated with a higher likelihood of ICU admission, need of MV, and death. SROCs revealed AUCs of 0.74, 0.80 and 0.71 for mortality, need of MV and ICU admission, respectively.

CONCLUSIONS

Blood NfL levels were elevated in the acute phase of COVID-19 patients without major CNS manifestations and associated with clinical severity and poor outcome. The marker might ameliorate the performance of prognostic multivariable algorithms in COVID-19.

Neurofilament light chain in cerebrospinal fluid as a novel biomarker in evaluating both clinical severity and therapeutic response in Niemann-Pick disease type C1

PURPOSE

Niemann-Pick disease type C1 (NPC1) is a neurodegenerative lysosomal disorder caused by pathogenic variants in NPC1. Disease progression is monitored using the NPC Neurological Severity Scale, but there are currently no established validated or qualified biomarkers. Neurofilament light chain (NfL) is being investigated as a biomarker in multiple neurodegenerative diseases.

METHODS

Cross-sectional and longitudinal cerebrospinal fluid (CSF) samples were obtained from 116 individuals with NPC1. NfL levels were measured using a solid-phase sandwich enzyme-linked immunosorbent assay and compared with age-appropriate non-NPC1 comparison samples.

RESULTS

Median levels of NfL were elevated at baseline (1152 [680-1840] pg/mL) in NPC1 compared with controls (167 [82-372] pg/mL; P < .001). Elevated NfL levels were associated with more severe disease as assessed by both the 17-domain and 5-domain NPC Neurological Severity Score. Associations were also observed with ambulation, fine motor, speech, and swallowing scores. Although treatment with the investigational drug 2-hydroxypropyl-β-cyclodextrin (adrabetadex) did not decrease CSF NfL levels, miglustat therapy over time was associated with a decrease (odds ratio = 0.77, 95% CI = 0.62-0.96).

CONCLUSION

CSF NfL levels are increased in individuals with NPC1, associated with clinical disease severity, and decreased with miglustat therapy. These data suggest that NfL is a biomarker that may have utility in future therapeutic trials.

Multiple sclerosis: Neuroimmune crosstalk and therapeutic targeting

Multiple sclerosis (MS) is a chronic inflammatory and degenerative disease of the central nervous system afflicting nearly three million individuals worldwide. Neuroimmune interactions between glial, neural, and immune cells play important roles in MS pathology and offer potential targets for therapeutic intervention. Here, we review underlying risk factors, mechanisms of MS pathogenesis, available disease modifying therapies, and examine the value of emerging technologies, which may address unmet clinical needs and identify novel therapeutic targets.

The multifaceted role of neurofilament light chain protein in non-primary neurological diseases

The advancing validation and exploitation of CSF and blood neurofilament light chain protein as a biomarker of neuroaxonal damage has deeply changed the current diagnostic and prognostic approach to neurological diseases. Further, recent studies have provided evidence of potential new applications of this biomarker also in non-primary neurological diseases. In the present review we summarize the state of the art, future perspectives, but also limitations, of neurofilament light chain protein as a CSF and blood biomarker in several medical fields, including intensive care medicine, surgery, internal medicine and psychiatry. In particular, neurofilament light chain protein is associated with the degree of neurological impairment and outcome in patients admitted to intensive care units or in the perioperative phase and it seems to be highly interconnected with cardiovascular risk factors. Beyond that, interesting diagnostic and prognostic insights have been provided by the investigation of neurofilament light chain protein in psychiatric disorders as well as in the current coronavirus disease-19 pandemic and in normal ageing. Altogether, current data outline a multifaceted applicability of CSF and blood neurofilament light chain protein ranging from the critical clinical setting to the development of precision medicine models suggesting a strict interplay between the nervous system pathophysiology and the health-illness continuum.

Plasma neurofilament light significantly decreases following treatment in Lyme neuroborreliosis and is not associated with persistent symptoms

BACKGROUND AND PURPOSE

Currently there is an unmet need for a highly standardized blood biomarker test to monitor treatment response in Lyme neuroborreliosis (LNB). Differentiating between active or past infection is challenged by the relatively high frequency of persistent symptoms after the end of antibiotic treatment (estimated 15%-20%), the variable clinical course and the long-lasting Borrelia burgdorferi antibodies. The aim was therefore to evaluate plasma neurofilament light chain (pNfL) as a marker for disease activity in LNB.

METHODS

This was a prospective cohort of definite LNB (N = 36) with blood samples and clinical evaluation including Glasgow Outcome Score at treatment initiation and 3 and 6 months' follow-up. Consecutive plasma was retrospectively analysed for the content of neurofilament light chain by Quanterix® kits (Simoa® NF-light Kit).

RESULTS

Plasma neurofilament light chain significantly decreased between treatment initiation and the 3-month follow-up (median 83 pg/ml vs. median 14 pg/ml (25 pairs), p < 0.0001). No significant change was observed between 3 and 6 months' follow-up (median 14 pg/ml vs. median 12 pg/ml (21 pairs), p = 0.33). At treatment initiation 90% had pNfL above the age-defined reference compared to only 23% and 7% respectively at 3 and 6 months' follow-up. Decreases in pNfL were mirrored by increasing Glasgow Outcome Score. Reporting persistent symptoms at the 6-month follow-up was not associated with pNfL (relative change from reference or actual values) at baseline or at 6 months' follow-up.

CONCLUSION

Plasma neurofilament light chain decreases following antibiotic treatment in LNB and is not associated with reporting persistent symptoms. It was therefore speculated that it may prove useful as a treatment response biomarker in LNB.

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.

Identifying Biomarkers of Spinal Muscular Atrophy for Further Development

BACKGROUND

Spinal muscular atrophy (SMA) is caused by bi-allelic, recessive mutations of the survival motor neuron 1 (SMN1) gene and reduced expression levels of the survival motor neuron (SMN) protein. Degeneration of alpha motor neurons in the spinal cord causes progressive skeletal muscle weakness. The wide range of disease severities, variable rates of decline, and heterogenous clinical responses to approved disease-modifying treatment remain poorly understood and limit the ability to optimize treatment for patients. Validation of a reliable biomarker(s) with the potential to support early diagnosis, inform disease prognosis and therapeutic suitability, and/or confirm response to treatment(s) represents a significant unmet need in SMA.

OBJECTIVES

The SMA Multidisciplinary Biomarkers Working Group, comprising 11 experts in a variety of relevant fields, sought to determine the most promising candidate biomarker currently available, determine key knowledge gaps, and recommend next steps toward validating that biomarker for SMA.

METHODS

The Working Group engaged in a modified Delphi process to answer questions about candidate SMA biomarkers. Members participated in six rounds of reiterative surveys that were designed to build upon previous discussions.

RESULTS

The Working Group reached a consensus that neurofilament (NF) is the candidate biomarker best poised for further development. Several important knowledge gaps were identified, and the next steps toward filling these gaps were proposed.

CONCLUSIONS

NF is a promising SMA biomarker with the potential for prognostic, predictive, and pharmacodynamic capabilities. The Working Group has identified needed information to continue efforts toward the validation of NF as a biomarker for SMA.

Association of neurofilament light chain with renal function: mechanisms and clinical implications

BACKGROUND

Blood-based neurofilament light chain (NfL) is a promising biomarker of neurodegeneration across multiple neurodegenerative diseases. However, blood-based NfL is highly associated with renal function in older adults, which leads to the concern that blood-based NfL levels may be influenced by renal function, rather than neurodegeneration alone. Despite growing interest in using blood-based NfL as a biomarker of neurodegeneration in research and clinical practices, whether renal function should always be accounted for in these settings remains unclear. Moreover, the mechanisms underlying this association between blood-based measures of NfL and renal function remain elusive. In this study, we first evaluated the effect of renal function on the associations of plasma NfL with other measures of neurodegeneration. We then examined the extent of genetic and environmental contributions to the association between plasma NfL and renal function.

METHODS

In a sample of 393 adults (mean age=75.22 years, range=54-90), we examined the associations of plasma NfL with cerebrospinal fluid (CSF) NfL and brain volumetric measures before and after adjusting for levels of serum creatinine (an index of renal function). In an independent sample of 969 men (mean age=67.57 years, range=61-73) that include monozygotic and dizygotic twin pairs, we replicated the same analyses and leveraged biometrical twin modeling to examine the genetic and environmental influences on the plasma NfL and creatinine association.

RESULTS

Plasma NfL's associations with cerebrospinal fluid NfL and brain volumetric measures did not meaningfully change after adjusting for creatinine levels. Both plasma NfL and creatinine were significantly heritable (h2=0.54 and 0.60, respectively). Their phenotypic correlation (r=0.38) was moderately explained by shared genetic influences (genetic correlation=0.46) and unique environmental influences (unique environmental correlation=0.27).

CONCLUSIONS

Adjusting for renal function is unnecessary when assessing associations between plasma NfL and other measures of neurodegeneration but is necessary if plasma NfL is compared to a cutoff for classifying neurodegeneration-positive versus neurodegeneration-negative individuals. Blood-based measures of NfL and renal function are heritable and share common genetic influences.

The 2022 Lady Estelle Wolfson lectureship on neurofilaments

Neurofilament proteins (Nf) have been validated and established as a reliable body fluid biomarker for neurodegenerative pathology. This review covers seven Nf isoforms, Nf light (NfL), two splicing variants of Nf medium (NfM), two splicing variants of Nf heavy (NfH), α -internexin (INA) and peripherin (PRPH). The genetic and epigenetic aspects of Nf are discussed as relevant for neurodegenerative diseases and oncology. The comprehensive list of mutations for all Nf isoforms covers Amyotrophic Lateral Sclerosis, Charcot-Marie Tooth disease, Spinal muscular atrophy, Parkinson Disease and Lewy Body Dementia. Next, emphasis is given to the expanding field of post-translational modifications (PTM) of the Nf amino acid residues. Protein structural aspects are reviewed alongside PTMs causing neurodegenerative pathology and human autoimmunity. Molecular visualisations of NF PTMs, assembly and stoichiometry make use of Alphafold2 modelling. The implications for Nf function on the cellular level and axonal transport are discussed. Neurofilament aggregate formation and proteolytic breakdown are reviewed as relevant for biomarker tests and disease. Likewise, Nf stoichiometry is reviewed with regard to in vitro experiments and as a compensatory mechanism in neurodegeneration. The review of Nf across a spectrum of 87 diseases from all parts of medicine is followed by a critical appraisal of 33 meta-analyses on Nf body fluid levels. The review concludes with considerations for clinical trial design and an outlook for future research.