Plasma neurofilament light chain (NfL) reference interval determination in an Age-stratified cognitively unimpaired cohort

Evidence that minocycline treatment confounds the interpretation of neurofilament as a biomarker

Neurofilament light (NfL) concentration in CSF and blood serves as an important biomarker in neurology drug development. Changes in NfL are generally assumed to reflect changes in neuronal damage, while little is known about the clearance of NfL from biofluids. In a study of asymptomatic individuals at risk for prion disease, both blood and CSF NfL spiked in one participant following a 6-week course of minocycline, absent any other biomarker changes and without subsequent onset of symptoms. We subsequently observed high NfL after minocycline treatment in discarded clinical plasma samples from inpatients, in mouse plasma and in conditioned media from neuron-microglia co-cultures. The specificity and kinetics of NfL response lead us to hypothesize that minocycline does not cause or exacerbate neuronal damage, but instead affects NfL by inhibiting its clearance, posing a potential confounder for the interpretation of this important biomarker.

Short- and long-term natural history of three neurodegenerative biomarkers among middle-aged and older adults

BACKGROUND

Little is known about the longitudinal trajectories of novel neurodegenerative biomarkers including neurofilament light (NfL), tau, and glial fibrillary acidic protein (GFAP).

OBJECTIVES

We aimed to investigate the short- and long-term natural history of these biomarkers measured longitudinally among healthy adults.

METHODS

In this cohort study from the Physicians' Health Study (PHS), VITamin D and OmegA-3 TriaL (VITAL), and COcoa Supplement and Multivitamin Outcomes Study (COSMOS), we included 1299 adults with bloods collected 2 years (VITAL and COSMOS) or 14 years (PHS) apart and without diagnosed neurodegenerative diseases before baseline or during follow-up through two years after the final blood collection. Associations between baseline characteristics and changes in NfL, tau, and GFAP were evaluated.

RESULTS

Mean (SD) age at baseline was 49.8 (6.8), 67.5 (6.2), and 70.3 (5.7) in PHS, VITAL, and COSMOS, respectively. PHS enrolled only men while ∼50% of the VITAL and COSMOS populations in this study were men. Median percent changes (IQR) of NfL were 40.6% (2.4, 58.2) increase over 14 years (PHS) and 8.5% (-6.6, 28.6) over 2 years (VITAL and COSMOS); increases in tau were 101% (10.7, 285) over 14 years and 11.8% (-35.2, 106) over 2 years; and increases in GFAP were 25.1% (-1.7, 23.8) over 14 years and 5.6% (-12.8, 28.6) over 2 years. In multivariable models, age was most strongly and robustly associated with 14-year changes in NfL and GFAP (adjusted p<0.001), and increases in levels accelerated at older ages. No baseline variables were associated with changes in tau.

CONCLUSION

Increases in NfL and GFAP accelerated with age, highlighting the need to improve our understanding of the clinical relevance of short- and long-term changes in these neurodegenerative biomarkers in large-scale, long-term cohorts.

Reference range for serum neurofilament light chain: findings from healthy Thai adults

Serum neurofilament light chain is a notable biomarker for detecting axonal injury and has shown significant potential for clinical applications. Establishing a reference interval and cut-off level is a critical step towards implementing a serum neurofilament light chain in routine clinical practice. In this study, we aimed to establish a reference range of serum neurofilament light chains for the Thai population. Blood samples were collected from healthy Thai adults without a history of neurological diseases and screened at the Siriraj Hospital. The relationship between age, sex and log10-transformed serum neurofilament light chain levels was analysed using linear regression. A crude reference interval was calculated as the 2.5-97.5th percentile values. An age-normative percentile curve for serum neurofilament light chain was derived using the generalized additive model for location, scale and shape. A total of 223 subjects (96 males and 127 females) aged 18-70 years were recruited. Male sex (P = 0.008) and older age (P  < 0.001) were significantly associated with higher serum neurofilament light chain levels. A median of the observed serum neurofilament light chain values was 5.8 pg/ml (95% confidence interval 5.4-6.2), ranging from 1.0 to 18.4 pg/ml, with a crude reference interval of 2.3-15.9 pg/ml. The 2.5-97.5th percentile intervals for serum neurofilament light chain by age group were as follows: 20-29 years (n = 57): 1.7-8.7 pg/ml; 30-39 years (n = 58): 2.5-10.6 pg/ml; 40-49 years (n = 59): 3.5-14.3 pg/ml; 50-59 years (n = 37): 4.7-15.8 pg/ml and 60-69 years (n = 12): 4.2-18.2 pg/ml. The age-normative serum neurofilament light chain curve predicted the 97.5th percentile of 8.2, 9.9, 11.7, 14.6 and 19.9 pg/ml for ages 20, 30, 40, 50 and 60, respectively. This study is the first to establish reference values for serum neurofilament light chains in Thailand. The age-normative upper reference curve is closely aligned with observed values and those previously reported in other studies, providing a robust framework for clinical implementation. However, further validation in larger cohorts and among individuals with neurological diseases is warranted.

A review of laboratory practices for CSF oligoclonal banding and associated tests

Multiple sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system, often emerging in early adulthood and representing a leading cause of neurological disability in young adults. Diagnosing MS involves a combination of clinical assessment, imaging and laboratory tests, with cerebrospinal fluid (CSF)-specific immunoglobulin G (IgG) oligoclonal bands (OCB) being an important marker for fulfilling the dissemination in time criteria. A recent survey of Canadian clinical laboratories highlighted considerable variation in OCB reporting practices nationwide, spanning quality control (QC) practices, acceptable time limits between paired CSF and serum sample collections, protocols for reporting band counts, interpretation and reporting of mirrored patterns, testing panels, and interpretive thresholds. These inconsistencies impact patient care and the comparability of laboratory results across different laboratories. The Harmonized CSF Analysis for MS Investigation (hCAMI) subcommittee of the Canadian Society of Clinical Chemists Reference Interval Harmonization Working Group was established to generate recommendations for laboratory processes and reporting of CSF OCB and associated tests supporting MS diagnosis. This review serves as a foundation for these efforts, summarizing the available evidence in areas where practice variations have been noted. This review begins by examining current practices and guidelines for standardized quality assurance, including optimal QC materials, frequency, documentation, and participation in external quality assurance programs. The disparity between paired CSF and serum sample acceptability time limits was further examined by reviewing current practices and recommendations as well as compiling evidence on IgG synthesis, turnover rate, biological variation, and stability in CSF and serum samples. Additionally, this review addresses the lack of consensus on reporting the number of CSF-specific and CSF-serum matched bands, focusing on interpreter variability and clinical utility. Contributing factors and clinical implications of mirror patterns, including discussion on monoclonal gammopathies and cases of matched bands of differing staining intensity, is provided. Testing panel components including adjunctive CSF tests, such as the IgG index, to support MS investigations despite their absence from clinical guidelines is also discussed. This review also provides a comprehensive analysis of current practices, guidelines, and the evidence surrounding different cutoffs for IgG index and CSF-specific bands.

Finally, the review considers emerging biomarkers, such as the kappa free light chain index and serum neurofilament light chain, which show promise for MS diagnosis and management. This comprehensive review of current practices, guidelines, and evolving evidence will guide the hCAMI subcommittee's efforts to harmonize CSF OCB analysis and improve MS diagnosis.

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.

Prevalence and Clinical Correlates of Cerebrovascular Alterations in Fabry Disease: A Cross-Sectional Study

Background/Objectives: Fabry disease (FD) is an inborn error of the glycosphingolipid metabolism with variable kidney, heart, and central nervous system (CNS) involvement. CNS-related FD manifestations include early ischemic stroke and white matter lesions (WMLs) related to cerebral small-vessel disease (CSVD), possibly resulting in cognitive impairment. We studied 40 adult FD patients (17 male) to assess: (i) prevalence of cerebrovascular and cognitive manifestations in FD and their correlation with heart and renal involvement; and (ii) the potential value of serum neurofilament light chain (NfL) levels as an indicator of WMLs in FD. Methods: Patients underwent detailed diagnostic assessment related to FD, also including Mainz Severity Score Index (MSSI), neuropsychological tests, brain MRI to assess WMLs by the modified Fazekas score (mFS), and NfL determination by single-molecule array (SiMoA) (n = 22 FD patients vs. 15 healthy controls). Results: Overall, 4 FD patients had a history of ischemic stroke and 13/32 patients (40.6%) had an mFS ≥ 1. Almost two-thirds of FD patients (27/39, 69.2%) showed impairment on at least one cognitive test. On univariate analysis, only a reduction in estimated glomerular filtration rate was associated with an increased likelihood of having WMLs on brain MRI. Serum NfL levels were higher in FD patients vs. controls, with a trend toward significance (p = 0.08). Conclusions: Mild-to-moderate CSVD is a characteristic brain "signature" in FD patients. Both cardiac and renal involvement correlate with WML load, but only renal involvement appears to be predictive of CNS damage. Brain microvascular damage is associated with mild cognitive impairment in FD, and serum NfL might represent a potential biomarker of CSVD in FD.

Elevated neurofilament light chain associated with cobalt/chromium metal neurotoxicity in a patient with a failed hip implant

BACKGROUND

It is known that the heavy metals cobalt and chromium are associated with neurotoxicity. Chromium (Cr) and Cobalt (Co) are both components of metal-on-metal (MoM) implants which can be degraded/fragmented and released into the bloodstream. Neurofilament Light Chain (NfL) is a neuron-specific protein that increases in serum following axonal damage. Here, we report a novel case of a patient with neurotoxic concentrations of serum Co and Cr stemming from fragments of a Metal on Metal (MoM) hip implant exhibiting elevated serum NfL concentrations.

CASE PRESENTATION

A 56-year-old female patient with ceramic and metal fragments left in her body after hip arthroplasty revision presented with symptoms consistent with Co/Cr neurotoxicity. Serum Co, Cr and NfL concentrations were measured to assess metal ion exposure and its potential link to her neurological symptoms. Over four months following two revision surgeries, her serum Co and Cr concentrations decreased significantly from their peak levels, along with a concomitant decrease in NfL concentrations. During this period, the patient's pathological neurological symptoms gradually resolved, with serum Co, Cr, and NfL concentrations approaching normal ranges.

CONCLUSION

Serum NfL is elevated in a patient exhibiting neurotoxicity from Co/Cr implant exposure. The potential utility of serum NfL as a biomarker for metal associated neurotoxicity should be further explored.

Association of plasma biomarkers of Alzheimer's pathology and neurodegeneration with gait performance in older adults

BACKGROUND

Declining gait performance is seen in aging individuals, due to neural and systemic factors. Plasma biomarkers provide an accessible way to assess evolving brain changes; non-specific neurodegeneration (NfL, GFAP) or evolving Alzheimer's disease (Aβ 42/40 ratio, P-Tau181).

METHODS

In a population-based cohort of older adults, we evaluate the hypothesis that plasma biomarkers of neurodegeneration and Alzheimer's Disease pathology are associated with worse gait performance. A sample of 2641 Mayo Clinic Study of Aging participants with measurements of plasma biomarkers and gait parameters was analyzed in this cross-sectional study. Linear regression models using plasma biomarkers as predictors of gait parameters and adjusted for age, sex, BMI, Charlson Comorbidity Index, and cognitive diagnosis were evaluated.

RESULTS

In this study multiple statistically significant relationships are observed for GFAP, NfL, and P-Tau181 with gait parameters. Each standard deviation increase in GFAP, NfL, and P-Tau181 is associated with a reduction in velocity of 2.100 (95% CI: -3.004, -1.196; p = 5.4 × 10-6), 4.400 (-5.292, -3.507; p = 9.5 × 10-22), and 2.617 (-3.414, -1.819; p = 1.5 × 10-10) cm/sec, respectively. Overall, NfL has the strongest associations with poor gait performance. Models with age interactions show that the strength of associations between the plasma biomarkers and the gait parameters became stronger with increasing age. There are no specific gait parameters that associate with individual plasma biomarkers.

CONCLUSION

Plasma biomarkers of neurodegeneration and Alzheimer's Disease pathology are not only markers of cognitive decline but also indicate motor decline in the aging population.

Neurofilament light chain as a biomarker for hereditary ATTR amyloidosis - correlation between neurofilament light chain and nerve conduction study

BACKGROUND

Neurofilament light chain (NfL) is a biomarker of neuronal injury in hereditary ATTR (ATTRv) amyloidosis. However, the correlation between NfL and nerve conduction study (NCS), the standard test for ATTRv neuropathy, has not been investigated.

OBJECTIVE

Elucidate the correlation between NfL and NCS parameters.

METHODS

227 serum NfL measurements were performed in 45 ATTRv patients, 5 asymptomatic carriers, and 12 controls. Among them, 177 simultaneous analyses of NCS and NfL were conducted in 45 ATTRv patients.

RESULTS

NfL levels of symptomatic patients were significantly higher than those of asymptomatic carriers and controls. Serum NfL levels were correlated with NCS parameters, especially compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes, indicators of axonal damage. CMAP and/or SNAP amplitudes were undetectable in 9 patients (no-amplitude group) due to advanced neuropathy. NfL levels in the no-amplitude group were significantly higher than those in patients with detectable CMAP/SNAP. NfL levels significantly decreased with patisiran, although no significant changes were observed in CMAP and SNAP.

CONCLUSIONS

NfL levels are found to be correlated with CMAP/SNAP amplitudes. Compared with NCS, NfL can be a more sensitive biomarker for detecting treatment response and active nerve damage even in patients with advanced neuropathy.

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.

Impact of Permissive Hypercapnia on Postoperative Early Plasma Neurofilament Light Chain in Elderly Patients Undergoing Laparoscopic Surgery: A Prospective, Randomized Controlled Trial

Background

The effects of intraoperative permissive hypercapnia (PaCO2 of 45-55 mmHg) on the central nervous system remain unclear. Neurofilament light chain (NfL, a protein found in the axons and nerve fibers of neurons) has been associated with central nervous system disorders. This study investigated the effect of intraoperative permissive hypercapnia on plasma NfL concentration 1 day postoperatively, and in turn on the central nervous system, during laparoscopic surgery.

Methods

This investigation was a prospective, single-blind randomized controlled trial. Eighty-four individuals aged above 60 years were randomly allocated to either the normocapnia group with an PaCO2 of 35-45 mmHg (n=42) or the hypercapnia group with a PaCO2 of 45-55 mmHg (n=42). The primary outcome was the 1-day postoperative plasma NfL concentration. Secondary outcomes included the area under the curve (AUC) values for PaCO2 and regional cerebral oxygen saturation (rSO2). The Mann-Whitney U-test was mainly used to analyze the outcomes.

Results

The final analysis included 38 and 40 patients in the normocapnia and hypercapnia groups, respectively. There was no statistically significant difference observed between the groups regarding the preoperative and 1-day postoperative plasma NfL concentration (14.0 [11.1, 19.9] vs 16.3 [9.06, 19.9] pg/mL, P>0.05; 23.4 [16.8, 32.3] vs 21.5 [15.6, 29.9] pg/mL, P>0.05, respectively). However, in both groups, the postoperative plasma concentration of NfL showed a significant increase when compared with the preoperative levels (both P < 0.001). The AUCs of PaCO2 and rSO2 from the beginning to the end of the pneumoperitoneum were significantly higher in the hypercapnia group compared with the normocapnia group (both P<0.05).

Conclusion

Our results indicate that intraoperative permissive hypercapnia targeting a PaCO2 of 45-55 mmHg does not significantly influence postoperative early plasma NfL elevation levels in elderly patients undergoing laparoscopic surgery. During general anesthesia, intraoperative permissive hypercapnia might not significantly impact the central nervous system.

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

BACKGROUND AND PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

METHODS

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

FINDINGS

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

INTERPRETATION

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

FUNDING

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

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Evidence that minocycline treatment confounds the interpretation of neurofilament as a biomarker

Neurofilament light (NfL) concentration in cerebrospinal fluid (CSF) and blood serves as an important biomarker in neurology drug development. Changes in NfL are generally assumed to reflect changes in neuronal damage, while little is known about the clearance of NfL from biofluids. We observed an NfL increase of 3.5-fold in plasma and 5.7-fold in CSF in an asymptomatic individual at risk for genetic prion disease following 6 weeks' treatment with oral minocycline for a dermatologic indication. Other biomarkers remained normal, and proteomic analysis of CSF revealed that the spike was exquisitely specific to neurofilaments. NfL dropped nearly to normal levels 5 weeks after minocycline cessation, and the individual remained free of disease 2 years later. Plasma NfL in dermatology patients was not elevated above normal controls. Dramatically high plasma NfL (>500 pg/mL) was variably observed in some hospitalized individuals receiving minocycline. In mice, treatment with minocycline resulted in variable increases of 1.3- to 4.0-fold in plasma NfL, with complete washout 2 weeks after cessation. In neuron-microglia co-cultures, minocycline increased NfL concentration in conditioned media by 3.0-fold without any visually obvious impact on neuronal health. We hypothesize that minocycline does not cause or exacerbate neuronal damage, but instead impacts the clearance of NfL from biofluids, a potential confounder for interpretation of this biomarker.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Translatable plasma and CSF biomarkers for use in mouse models of Huntington's disease

Huntington's disease is an inherited neurodegenerative disorder for which a wide range of disease-modifying therapies are in development and the availability of biomarkers to monitor treatment response is essential for the success of clinical trials. Baseline levels of neurofilament light chain in CSF and plasma have been shown to be effective in predicting clinical disease status, subsequent clinical progression and brain atrophy. The identification of further sensitive prognostic fluid biomarkers is an active research area, and total-Tau and YKL-40 levels have been shown to be increased in CSF from Huntington's disease mutation carriers. The use of readouts with clinical utility in the preclinical assessment of potential therapeutics should aid in the translation of new treatments. Here, we set out to determine how the concentrations of these three proteins change in plasma and CSF with disease progression in representative, well-established mouse models of Huntington's disease. Plasma and CSF were collected throughout disease progression from R6/2 transgenic mice with CAG repeats of 200 or 90 codons (R6/2:Q200 and R6/2:Q90), zQ175 knock-in mice and YAC128 transgenic mice, along with their respective wild-type littermates. Neurofilament light chain and total-Tau concentrations were quantified in CSF and plasma using ultrasensitive single-molecule array (Quanterix) assays, and a novel Quanterix assay was developed for breast regression protein 39 (mouse homologue of YKL-40) and used to quantify breast regression protein 39 levels in plasma. CSF levels of neurofilament light chain and plasma levels of neurofilament light chain and breast regression protein 39 increased in wild-type biofluids with age, whereas total-Tau remained constant. Neurofilament light chain and breast regression protein 39 were elevated in the plasma and CSF from Huntington's disease mouse models, as compared with wild-type littermates, at presymptomatic stages, whereas total-Tau was only increased at the latest disease stages analysed. Levels of biomarkers that had been measured in the same CSF or plasma samples taken at the latest stages of disease were correlated. The demonstration that breast regression protein 39 constitutes a robust plasma biomarker in Huntington's disease mouse models supports the further investigation of YKL-40 as a CSF biomarker for Huntington's disease mutation carriers. Neurofilament light chain and Tau are considered markers of neuronal damage, and breast regression protein 39 is a marker of inflammation; the similarities and differences in the levels of these proteins between mouse models may provide future insights into their underlying pathology. These data will facilitate the use of fluid biomarkers in the preclinical assessment of therapeutic agents for Huntington's disease, providing readouts with direct relevance to clinical trials.

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.

Biological variation estimates for serum neurofilament light chain in healthy subjects

OBJECTIVES

Neurofilament light chain (NfL) is an emerging biomarker of neurodegeneration disorders. Knowledge of the biological variation (BV) can facilitate proper interpretation between serial measurements. Here BV estimates for serum NfL (sNfL) are provided.

METHODS

Serum samples were collected weekly from 24 apparently healthy subjects for 10 consecutive weeks and analyzed in duplicate using the Siemens Healthineers sNfL assay on the Atellica® IM Analyzer. Outlier detection, variance homogeneity analyses, and trend analysis were performed followed by CV-ANOVA to determine BV and analytical variation (CVA) estimates with 95%CI and the associated reference change values (RCV) and analytical performance specifications (APS).

RESULTS

Despite observed differences in sNfL concentrations between males and females, BV estimates remained consistent across genders. Both within-subject BV (CVI) for males (10.7%, 95%CI; 9.2-12.6) and females (9.1%, 95%CI; 7.8-10.9) and between-subject BV (CVG) for males (26.1%, 95%CI; 18.0-45.6) and females (30.2%, 95%CI; 20.9-53.5) were comparable. An index of individuality value of 0.33 highlights significant individuality, indicating the potential efficacy of personalized reference intervals in patient monitoring.

CONCLUSIONS

The established BV estimates for sNfL underscore its potential as a valuable biomarker for monitoring neurodegenerative diseases, offering a foundation for improved decision-making in clinical settings.

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.

The performance of plasma phosphorylated tau231 in detecting Alzheimer's disease: A systematic review with meta-analysis

Cerebrospinal fluid (CSF) phosphorylated tau231 (P-tau231) is associated with neuropathological outcomes of Alzheimer's disease (AD). The invasive access of cerebrospinal fluid has greatly stimulated interest in the identification of blood-based P-tau231, and the recent advent of single-molecule array assay for the quantification of plasma P-tau231 may provide a turning point to evaluate the usefulness of P-tau231 as an AD-related biomarker. Yet, in the plasma P-tau231 literature, findings with regard to its diagnostic utility have been inconsistent, and thus, we aimed to statistically investigate the potential of plasma P-tau231 in the context of AD via meta-analysis. Publications on plasma P-tau231 were systematically retrieved from PubMed, EMBASE, the Cochrane library and Web of Science databases. A total of 10 studies covering 2007 participants were included, and we conducted random-effect or fixed-effect meta-analysis, sensitivity analysis and publication bias analysis using the STATA SE 14.0 software. According to our quantitative integration, plasma P-tau231 increased from cognitively unimpaired (CU) populations to mild cognitive impairment to AD and showed significant changes in pairwise comparisons of AD, mild cognitive impairment and CU. Plasma P-tau231 level was significantly higher in CU controls with positive amyloid-β (Aβ) status compared with Aβ-negative CU group. Additionally, the excellent diagnostic accuracy of plasma P-tau231 for asymptomatic Aβ pathology was verified by the pooled value of area under the receiver operating characteristic curves (standard mean difference [95% confidence interval]: .75 [.69, .81], P < 0.00001). Overall, the increased plasma P-tau231 concentrations were found in relation to the early development and progression of AD.

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.

Effects of a 2-year exercise training on neuromuscular system health in older individuals with low muscle function

BACKGROUND

Ageing is accompanied by a progressive loss of skeletal muscle mass and strength, potentially determining the insurgence of sarcopenia. Evidence suggests that motoneuron and neuromuscular junction (NMJ) degeneration contribute to sarcopenia pathogenesis. Seeking for strategies able to slow down sarcopenia insurgence and progression, we investigated whether a 2-year mixed-model training involving aerobic, strength and balance exercises would be effective for improving or preserving motoneuronal health and NMJ stability, together with muscle mass, strength and functionality in an old, sarcopenic population.

METHODS

Forty-five sarcopenic elderly (34 females; 11 males) with low dual-energy X-ray absorptiometry (DXA) lean mass and Short Physical Performance Battery (SPPB) score <9 were randomly assigned to either a control group [Healthy Aging Lifestyle Education (HALE), n = 21] or an intervention group [MultiComponent Intervention (MCI), n = 24]. MCI trained three times per week for 2 years with a mix of aerobic, strength and balance exercises matched with nutritional advice. Before and after the intervention, ultrasound scans of the vastus lateralis (VL), SPPB and a blood sample were obtained. VL architecture [pennation angle (PA) and fascicle length (Lf)] and cross-sectional area (CSA) were measured. As biomarkers of neuronal health and NMJ stability status, neurofilament light chain (NfL) and C-terminal agrin fragment (CAF) concentrations were measured in serum. Differences in ultrasound parameters, NfL and CAF concentration and physical performance between baseline and follow-up were tested with mixed ANOVA or Wilcoxon test. The relationship between changes in physical performance and NfL or CAF concentration was assessed through correlation analyses.

RESULTS

At follow-up, MCI showed preserved VL architecture (PA, Lf) despite a reduced CSA (-8.4%, P < 0.001), accompanied by maintained CAF concentration and ameliorated overall SPPB performance (P = 0.007). Conversely, HALE showed 12.7% decrease in muscle CSA (P < 0.001), together with 5.1% and 5.5% reduction in PA and Lf (P < 0.001 and P = 0.001, respectively), and a 6.2% increase in CAF (P = 0.009) but improved SPPB balance score (P = 0.007). NfL concentration did not change in either group. In the population, negative correlations between changes in CAF concentration and SPPB total score were found (P = 0.047), whereas no correlation between NfL and SPPB variations was observed.

CONCLUSIONS

The present findings suggest that our 2-year mixed aerobic, strength and balance training seemed effective for preventing the age and sarcopenia-related increases in CAF concentration, preserving NMJ stability as well as muscle structure (PA and Lf) and improving physical performance in sarcopenic older individuals.

Review of Neurofilaments as Biomarkers in Sepsis-Associated Encephalopathy

Sepsis is a common and fatal disease, especially in critically ill patients. Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction with acute altered consciousness, permanent cognitive impairment, and even coma, accompanied by sepsis, without direct central nervous system infection. When managing SAE, early identification and quantification of axonal damage facilitate faster and more accurate diagnosis and prognosis. Although no specific markers for SAE have been identified, several biomarkers have been proposed. Neurofilament light chain (NFL) is a highly expressed cytoskeletal component of neurofilament (NF) proteins that can be found in blood and cerebrospinal fluid (CSF) after exposure to axonal injury. NFs can be used as diagnostic and prognostic biomarkers for sepsis-related brain injury. Phosphorylation of NFs contributes to the maturation and stabilization of cytoskeletal structures, especially axons, and facilitates axonal transport, including mitochondrial transport and energy transport. The stability of NF proteins can be assessed by monitoring the expression of NF genes. Furthermore, phosphorylation levels of NFs can be monitored to determine mitochondrial axonal transport associated with cellular energy metabolism at distal axons to assess progression during SAE treatment. This paper provides new insights into the biological characteristics, detection techniques, and scientific achievements of NFs, and discusses the underlying mechanisms and future research directions of NFs in SAE.

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.