Plasma neurofilament light levels are associated with risk of disability in multiple sclerosis

Determinants and Biomarkers of Progression Independent of Relapses in Multiple Sclerosis

Clinical, pathological, and imaging evidence in multiple sclerosis (MS) suggests that a smoldering inflammatory activity is present from the earliest stages of the disease and underlies the progression of disability, which proceeds relentlessly and independently of clinical and radiological relapses (PIRA). The complex system of pathological events driving "chronic" worsening is likely linked with the early accumulation of compartmentalized inflammation within the central nervous system as well as insufficient repair phenomena and mitochondrial failure. These mechanisms are partially lesion-independent and differ from those causing clinical relapses and the formation of new focal demyelinating lesions; they lead to neuroaxonal dysfunction and death, myelin loss, glia alterations, and finally, a neuronal network dysfunction outweighing central nervous system (CNS) compensatory mechanisms. This review aims to provide an overview of the state of the art of neuropathological, immunological, and imaging knowledge about the mechanisms underlying the smoldering disease activity, focusing on possible early biomarkers and their translation into clinical practice. ANN NEUROL 2024;96:1-20.

Neuroaxonal damage in natalizumab-treated MS patients: The role of JCV antibody titres

BACKGROUND

While John Cunningham virus (JCV) is known to cause neuronal damage in progressive multifocal leukoencephalopathy (PML) among natalizumab-treated MS patients, its association with axonal loss in non-PML conditions remains unclear.

METHODS

In a cohort of 128 natalizumab-treated MS patients, serum neurofilament (sNfL) levels and JCV antibody titres were measured.

RESULTS

Among 128 patients (mean age = 38.4 years, 71.9% female), 51 (40%) were JCV positive. NfL levels increased by 15.3% for JCV index <0.7 (95% confidence interval [CI] = 0.963-1.381), by 18.6% for index 0.7-1.5 (95% CI = 1.009-1.394) and by 21.1% for index >1.5 (95% CI = 1.040-1.409) compared to JCV negative patients.

CONCLUSION

These findings indicate a potential link between JCV burden and neuroaxonal degeneration in natalizumab-treated MS patients.

Optical coherence tomography angiography suggests different retinal pathologies in multiple sclerosis and Sjögren's syndrome

BACKGROUND

While retinal vessel changes are evident in the eyes of patients with relapsing-remitting multiple sclerosis (RRMS), changes in the vasculature of possible MS mimics such as primary Sjögren's syndrome (pSS) remain to be determined. We investigated the potential of retinal optical coherence tomography (OCT) angiography (OCTA) as diagnostic tool to differentiate between patients with RRMS and pSS.

METHODS

This cross-sectional study included patients with RRMS (n = 36), pSS (n = 36) and healthy controls (n = 30). Participants underwent clinical examination, assessment of visual acuity, retinal OCT, OCTA, and serum markers of glial and neuronal damage. We investigated the associations between OCTA parameters, visual functions, and serum markers. Eyes with a history of optic neuritis (ON) were excluded from analysis.

RESULTS

We observed a significant thinning of the combined ganglion cell and inner plexiform layer in the eyes of patients with RRMS but not with pSS, when compared to healthy controls. Retinal vessel densities of the superficial vascular complex (SVC) were reduced in both patients with RRMS and pSS. However, retinal vessel rarefication of the deep vascular complex (DVC) was only evident in patients with pSS but not RRMS. Using multivariate regression analysis, we found that DVC vessel loss in pSS patients was associated with worse visual acuity.

CONCLUSIONS

Compared to patients with RRMS, rarefication of deep retinal vessels is a unique characteristic of pSS and associated with worse visual function. Assuming a disease-specific retinal vessel pathology, these data are indicative of a differential affliction of the gliovascular complex in the retina of RRMS and pSS patients.

Serum NfL and EGFR/NfL ratio mRNAs as biomarkers for phenotype and disease severity of myelin oligodendrocyte glycoprotein IgG-associated disease

Background and purpose

Myelin oligodendrocyte glycoprotein (MOG) IgG is frequently elevated in pediatric patients with acquired demyelinating syndrome (ADS). However, no specific biomarkers exist for phenotype classification, symptom severity, prognosis, and treatment guidance of MOG-IgG-associated disease (MOGAD). This study evaluated neurofilament light chain (NfL) and endothelial growth factor receptor (EGFR) mRNA expression levels in serum and cerebrospinal fluid (CSF) as potential biomarkers for MOGAD in Chinese children.

Methods

This was a cross-sectional and single-center study. We enrolled 22 consecutive pediatric patients hospitalized with MOGAD and 20 control pediatric patients hospitalized for noninflammatory neurological diseases in Hebei Children's Hospital. Serum and CSF were collected from MOGAD patients within 3 days before immunotherapy. The mRNA levels of NfL and EGFR in serum and CSF were measured by real-time polymerase chain reaction (qPCR), and the EGFR/NfL ratio mRNA was calculated. These measurement values were then compared between disease groups and among MOGAD phenotypes. In addition, the correlations between the mRNAs of three markers (NfL, EGFR, EGFR/NfL ratio), extended disability status scale (EDSS) scores, and clinical phenotypes were analyzed.

Results

Serum and CSF NfL mRNA levels were significantly higher of acute-stage MOGAD patients than those of control patients (p< 0.05 and p< 0.01, respectively), while the mRNA levels of serum EGFR and EGFR/NfL ratio were significantly lower of MOGAD patients than those of controls (p < 0.05, p < 0.0001). Serum NfL mRNA was significantly correlated with mRNA of serum EGFR (r =0.480, p < 0.05). Serum and CSF NfL mRNA levels in MOGAD patients with the ADEM-like phenotype were also significantly higher than those in control patients (p < 0.01, p < 0.01) and optic neuritis (ON) phenotype (p < 0.05, p < 0.05). Both mRNAs of NfL in CSF and EGFR/NfL ratio in serum were correlated with EDSS scores (p < 0.05, r = 0.424; p < 0.05, r= -0.521).

Conclusion

The mRNA levels of elevated NfL in serum and CSF as well as lower EGFR and EGFR/NfL ratio in serum could help distinguish acute-phase MOGAD. Higher mRNA levels of NfL in serum and CSF of MOGAD patients help distinguish ADEM-like phenotype. In addition, serum EGFR/NfL mRNA ratio is indicative of disease severity in pediatric patients with MOGAD. Further investigations are warranted to elucidate the pathological mechanisms underlying these associations.

Baseline serum neurofilament light chain levels differentiate aggressive from benign forms of relapsing-remitting multiple sclerosis: a 20-year follow-up cohort

BACKGROUND AND OBJECTIVES

Serum biomarkers are emerging as useful prognostic tools for multiple sclerosis (MS); however, long-term studies are lacking. We aimed to evaluate the long-term prognostic value of the serum levels of neurofilament light chain (NfL), total tau, glial fibrillary acidic protein (GFAP), and chitinase 3-like-1 (CHI3L1) measured close to the time of MS onset.

METHODS

In this retrospective, exploratory, observational, case and controls study, patients with relapsing-remitting MS (RRMS) with available baseline serum samples and prospectively follow-up in our MS unit for a long time were selected based on their clinical evolution to form two groups: (1) a benign RRMS (bRRMS) group, defined as patients with an Expanded Disability Status Scale (EDSS) score of ≤ 3 at ≥ 10 years of follow-up; (2) an aggressive RRMS (aRRMS) group, defined as patients with an EDSS score of ≥ 6 at ≤ 15 years of follow-up. An age-matched healthy control (HC) group was selected. NfL, total tau, and GFAP serum levels were quantified using a single-molecule array (SIMOA), and CHI3L1 was quantified using ELISA.

RESULTS

Thirty-one patients with bRRMS, 19 with aRRMS, and 10 HC were included. The median follow-up time from sample collection was 17.74 years (interquartile range, 14.60-20.37). Bivariate and multivariate analyses revealed significantly higher NfL and GFAP levels in the aRRMS group than in the bRRMS group. A receiver operating characteristic curve analysis identified serum NfL level as the most efficient marker for distinguishing aRRMS from bRRMS.

DISCUSSION

This proof-of-concept study comparing benign and aggressive RRMS groups reinforces the potential role of baseline NfL serum levels as a promising long-term disability prognostic marker. In contrast, serum GFAP, total tau, and CHI3L1 levels demonstrated a lower or no ability to differentiate between the long-term outcomes of RRMS.

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

BACKGROUND

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

METHODS

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

RESULTS

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

DISCUSSION

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

HIGHLIGHTS

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

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.

Recent Advances in Diagnostic, Prognostic, and Disease-Monitoring Biomarkers in Multiple Sclerosis

Multiple sclerosis (MS) is a highly heterogeneous disease. Currently, a combination of clinical features, MRI, and cerebrospinal fluid markers are used in clinical practice for diagnosis and treatment decisions. In recent years, there has been considerable effort to develop novel biomarkers that better reflect the pathologic substrates of the disease to aid in diagnosis and early prognosis, evaluation of ongoing inflammatory activity, detection and monitoring of disease progression, prediction of treatment response, and monitoring of disease-modifying treatment safety. In this review, the authors provide an overview of promising recent developments in diagnostic, prognostic, and disease-monitoring/treatment-response biomarkers in MS.

Plasma glial fibrillary acidic protein levels correlate with paramagnetic rim lesions in people with radiologically isolated syndrome

BACKGROUND

There are no specific, evidence-based recommendations for the management of individuals with radiologically isolated syndrome. Imaging and blood biomarkers may have prognostic utility.

OBJECTIVE

To determine whether plasma neurofilament light protein (NfL) or glial fibrillary acidic protein (GFAP) levels in people with radiologically isolated syndrome correlate with imaging measures that have been shown to be associated with negative clinical outcomes in people with multiple sclerosis.

METHODS

Cross-sectional analysis of people with radiologically isolated syndrome. Participants underwent magnetic resonance imaging (MRI) of the brain and cervical spinal cord, and plasma was collected. Plasma NfL and GFAP levels were measured with a single-molecule array, and correlations with MRI measures were assessed, including the number of: T1-black holes, white-matter lesions demonstrating the central vein sign, paramagnetic rim lesions, cervical spinal cord lesions and infratentorial lesions.

RESULTS

Plasma GFAP levels, but not NfL levels, showed correlations with the number of T1-black holes, white matter lesions demonstrating the central vein sign and paramagnetic rim lesions (all p < 0.05).

CONCLUSION

We found correlations between plasma GFAP levels and imaging measures associated with poor clinical outcomes and chronic inflammation in individuals with radiologically isolated syndrome. Plasma GFAP may have prognostic utility in clinical trials and clinical practice.

Association of magnetic resonance imaging phenotypes and serum biomarker levels with treatment response and long-term disease outcomes in multiple sclerosis patients

BACKGROUND AND PURPOSE

The aim was to evaluate whether magnetic resonance imaging (MRI) phenotypes defined by inflammation and neurodegeneration markers correlate with serum levels of neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in relapsing-remitting multiple sclerosis (RRMS) patients; and to explore the role of radiological phenotypes and biomarker levels on treatment response and long-term prognostic outcomes.

METHODS

Magnetic resonance imaging scans from 80 RRMS patients were classified at baseline of interferon-beta (IFNβ) treatment into radiological phenotypes defined by high and low inflammation and high and low neurodegeneration, based on the number of contrast-enhancing lesions, brain parenchymal fraction and the relative volume of non-enhancing black holes on T1-weighted images. Serum levels of NfL and GFAP were measured at baseline with single molecule array (Simoa) assays. MRI phenotypes and serum biomarker levels were investigated for their association with IFNβ response, and times to second-line therapies, secondary-progressive MS (SPMS) conversion and Expanded Disability Status Scale (EDSS) 6.0.

RESULTS

Mean (SD) follow-up was 17 (2.9) years. Serum NfL levels and GFAP were higher in the high inflammation (p = 0.04) and high neurodegeneration phenotypes (p = 0.03), respectively. The high inflammation phenotype was associated with poor response to IFNβ treatment (p = 0.04) and with shorter time to second-line therapies (p = 0.04). In contrast, the high neurodegeneration phenotype was associated with shorter time to SPMS (p = 0.006) and a trend towards shorter time to EDSS 6.0 (p = 0.09). High serum NfL levels were associated with poor response to IFNβ treatment (p = 0.004).

CONCLUSIONS

Magnetic resonance imaging phenotypes defined by inflammation and neurodegeneration correlate with serum biomarker levels, and both have prognostic implications in treatment response and long-term disease outcomes.

Normative Values for Serum Neurofilament Light Chain in US Adults

BACKGROUND AND PURPOSE

Neurofilament light chain (NfL) levels serve as a marker of neuroaxonal injury and can be measured in both cerebrospinal fluid and serum. Although serum NfL (sNfL) levels have been shown to increase with the progression of various neurological conditions, normative values for healthy individuals have not yet been established. This study was undertaken to determine age-specific normative values for sNfL and evaluate the associations between sNfL and sociodemographic characteristics.

METHODS

A retrospective analysis was conducted using population-based data collected by the National Health and Nutrition Examination Survey between 2013 and 2014. The sera of 2071 adult participants were collected. General linear models were used to examine the associations between sNfL levels and sample characteristics.

RESULTS

The data analysis revealed a significant positive association between age and sNfL levels (p<0.001). Sex was also associated with sNfL levels (p=0.04) after controlling for age. The mean sNfL levels for males and females were 17.99 pg/mL (95% confidence interval [CI]=15.43-20.17) and 15.78 pg/mL (95% CI=13.00-18.55) respectively, after controlling for age.

CONCLUSIONS

These results suggest that sNfL levels increase with age and are affected by sex. The findings of this study provide a useful baseline for comparing sNfL levels in clinical practice and future research.

Neurofilament Light Chain in Adult and Pediatric Multiple Sclerosis: A Promising Biomarker to Better Characterize Disease Activity and Personalize MS Treatment

Many biological markers have been explored in multiple sclerosis (MS) to better quantify disease burden and better evaluate response to treatments, beyond clinical and MRI data. Among these, neurofilament light chain (Nf-L), although non-specific for this disease and found to be increased in other neurological conditions, has been shown to be the most promising biomarker for assessing axonal damage in MS, with a definite role in predicting the development of MS in patients at the first neurological episode suggestive of MS, and also in a preclinical phase. There is strong evidence that Nf-L levels are increased more in relapsing versus stable MS patients, and that they predict future disease evolution (relapses, progression, MRI measures of activity/progression) in MS patients, providing information on response to therapy, helping to anticipate clinical decisions in patients with an apparently stable evolution, and identifying patient non-responders to disease-modifying treatments. Moreover, Nf-L can contribute to the better understanding of the mechanisms of demyelination and axonal damage in adult and pediatric MS. A fundamental requirement for its clinical use is the accurate standardization of normal values, corrected for confounding factors, in particular age, sex, body mass index, and presence of comorbidities. In this review, a guide is provided to update clinicians on the use of Nf-L in clinical activity.

Association between serum multi-protein biomarker profile and real-world disability in multiple sclerosis

Few studies examined blood biomarkers informative of patient-reported outcome (PRO) of disability in people with multiple sclerosis (MS). We examined the associations between serum multi-protein biomarker profiles and patient-reported MS disability. In this cross-sectional study (2017-2020), adults with diagnosis of MS (or precursors) from two independent clinic-based cohorts were divided into a training and test set. For predictors, we examined seven clinical factors (age at sample collection, sex, race/ethnicity, disease subtype, disease duration, disease-modifying therapy [DMT], and time interval between sample collection and closest PRO assessment) and 19 serum protein biomarkers potentially associated with MS disease activity endpoints identified from prior studies. We trained machine learning (ML) models (Least Absolute Shrinkage and Selection Operator regression [LASSO], Random Forest, Extreme Gradient Boosting, Support Vector Machines, stacking ensemble learning, and stacking classification) for predicting Patient Determined Disease Steps (PDDS) score as the primary endpoint and reported model performance using the held-out test set. The study included 431 participants (mean age 49 years, 81% women, 94% non-Hispanic White). For binary PDDS score, combined feature input of routine clinical factors and the 19 proteins consistently outperformed base models (comprising clinical features alone or clinical features plus one single protein at a time) in predicting severe (PDDS ≥ 4) versus mild/moderate (PDDS < 4) disability across multiple machine learning approaches, with LASSO achieving the best area under the curve (AUCPDDS = 0.91) and other metrics. For ordinal PDDS score, LASSO model comprising combined clinical factors and 19 proteins as feature input (R2PDDS = 0.31) again outperformed base models. The two best-performing LASSO models (i.e., binary and ordinal PDDS score) shared six clinical features (age, sex, race/ethnicity, disease subtype, disease duration, DMT efficacy) and nine proteins (cluster of differentiation 6, CUB-domain-containing protein 1, contactin-2, interleukin-12 subunit-beta, neurofilament light chain [NfL], protogenin, serpin family A member 9, tumor necrosis factor superfamily member 13B, versican). By comparison, LASSO models with clinical features plus one single protein at a time as feature input did not select either NfL or glial fibrillary acidic protein (GFAP) as a final feature. Forcing either NfL or GFAP as a single protein feature into models did not improve performance beyond clinical features alone. Stacking classification model using five functional pathways to represent multiple proteins as meta-features implicated those involved in neuroaxonal integrity as significant contributors to predictive performance. Thus, serum multi-protein biomarker profiles improve the prediction of real-world MS disability status beyond clinical profile alone or clinical profile plus single protein biomarker, reaching clinically actionable performance.

Serum levels of neurofilament light chains in pediatric multiple sclerosis: a systematic review and meta-analysis

BACKGROUND

Multiple sclerosis is a neuro-inflammatory disease that affects adults and children and causes somatic and cognitive symptoms. Diagnosis after the first clinical symptoms is challenging, involves laboratory and magnetic resonance imaging work-up and is often inconclusive unless subsequent clinical attacks occur. Neurofilament light chains are structural proteins within neurons. Levels of this marker in cerebrospinal fluid, plasma and serum are consistently higher in patients with an initial clinical demyelinating attack that later go on to develop multiple sclerosis. Evidence concerning serum levels of this biomarker in children with multiple sclerosis is scarce. Our aim is to review and analyze the evidence available for patients with multiple sclerosis, under the age of 18.

METHODS

We conducted a systematic search of PubMed/Medline, Embase, Cochrane Database, and ProQuest. Human studies that provided data on serum levels of Neurofilament light chains in pediatric patients with MS, measured at the time of the first demyelinating attack and before treatment were included in meta-analysis.

RESULTS

Three studies satisfied the inclusion criteria. 157 pediatric patients with multiple sclerosis and 270 hospital-based controls that did not present with this condition were included in the analysis. A fixed effects meta-analysis showed that the standardized mean difference between patients and controls is 1.82, with a 95% confidence interval of [1.56-2.08].

CONCLUSION

Pediatric patients with multiple sclerosis show higher levels of serum neurofilament light chains at their first clinical demyelinating attack compared to pediatric hospital-based controls.

Teriflunomide and Epstein-Barr virus in a Spanish multiple sclerosis cohort: in vivo antiviral activity and clinical response

Background

Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6) have been associated with multiple sclerosis (MS). Teriflunomide is an oral disease-modifying therapy approved for treatment of relapsing forms of MS. In the preclinical Theiler's murine encephalitis virus model of MS, the drug demonstrated an increased rate of viral clearance versus the vehicle placebo. Furthermore, teriflunomide inhibits lytic EBV infection in vitro.

Objective

1. To evaluate the humoral response against EBV and HHV-6 prior to teriflunomide treatment and 6 months later. 2. To correlate the variation in the humoral response against EBV and HHV-6 with the clinical and radiological response after 24 months of treatment with teriflunomide. 3. To analyze the utility of different demographic, clinical, radiological, and environmental data to identify early biomarkers of response to teriflunomide.

Methods

A total of 101 MS patients (62 women; mean age: 43.4 years) with one serum prior to teriflunomide onset and another serum sample 6 months later were recruited. A total of 80 had been treated for at least 24 months, 13 had stopped teriflunomide before 24 months, and 8 were currently under teriflunomide therapy but with less than 24 months of follow-up. We analyzed the levels of the viral antibodies titers abovementioned in serum samples with ELISA commercial kits, and the levels of serum neurofilament light chain (Nf-L).

Results

Antiviral antibody titers decreased for EBNA-1 IgG (74.3%), VCA IgG (69%), HHV-6 IgG (60.4%), and HHV-6 IgM (73.3%) after 6 months of teriflunomide. VCA IgG titers at baseline correlated with Nf-L levels measured at the same time (r = 0.221; p = 0.028) and 6 months later (r = 0.240; p = 0.017). We found that higher EBNA-1 titers (p = 0.001) and a higher age (p = 0.04) at baseline were associated with NEDA-3 conditions. Thus, 77.8% of patients with EBNA-1 >23.0 AU and >42.8 years (P50 values) were NEDA-3.

Conclusion

Treatment with teriflunomide was associated with a reduction of the levels of IgG antibody titers against EBV and HHV-6. Furthermore, higher EBNA-1 IgG titers prior to teriflunomide initiation were associated with a better clinical response.

Emerging imaging and liquid biomarkers in multiple sclerosis

The advent of highly effective disease modifying therapy has transformed the landscape of multiple sclerosis (MS) care over the last two decades. However, there remains a critical, unmet need for sensitive and specific biomarkers to aid in diagnosis, prognosis, treatment monitoring, and the development of new interventions, particularly for people with progressive disease. This review evaluates the current data for several emerging imaging and liquid biomarkers in people with MS. MRI findings such as the central vein sign and paramagnetic rim lesions may improve MS diagnostic accuracy and evaluation of therapy efficacy in progressive disease. Serum and cerebrospinal fluid levels of several neuroglial proteins, such as neurofilament light chain and glial fibrillary acidic protein, show potential to be sensitive biomarkers of pathologic processes such as neuro-axonal injury or glial-inflammation. Additional promising biomarkers, including optical coherence tomography, cytokines and chemokines, microRNAs, and extracellular vesicles/exosomes, are also reviewed, among others. Beyond their potential integration into MS clinical care and interventional trials, several of these biomarkers may be informative of MS pathogenesis and help elucidate novel targets for treatment strategies.

Clinical validation of a multi-protein, serum-based assay for disease activity assessments in multiple sclerosis

An 18-protein multiple sclerosis (MS) disease activity (DA) test was validated based on associations between algorithm scores and clinical/radiographic assessments (N = 614 serum samples; Train [n = 426; algorithm development] and Test [n = 188; evaluation] subsets). The multi-protein model was trained based on presence/absence of gadolinium-positive (Gd+) lesions and was also strongly associated with new/enlarging T2 lesions, and active versus stable disease (composite of radiographic and clinical evidence of DA) with improved performance (p < 0.05) compared to the neurofilament light single protein model. The odds of having ≥1 Gd + lesions with a moderate/high DA score were 4.49 times that of a low DA score, and the odds of having ≥2 Gd + lesions with a high DA score were 20.99 times that of a low/moderate DA score. The MSDA Test was clinically validated with improved performance compared to the top-performing single-protein model and can serve as a quantitative tool to enhance the care of MS patients.

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

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

Association of Serum Neurofilament Light Chain Levels at Disease Onset With Disability Worsening in Patients With a First Demyelinating Multiple Sclerosis Event Not Treated With High-Efficacy Drugs

Importance

The value of serum neurofilament light chain (sNfL) levels for predicting long-term disability in patients with multiple sclerosis (MS) remains controversial.

Objective

To assess whether high sNfL values are associated with disability worsening in patients who underwent their first demyelinating MS event.

Design, Setting, and Participants

This multicenter cohort study included patients who underwent their first demyelinating event suggestive of MS at Hospital Universitario Ramón y Cajal (development cohort; June 1, 1994, to September 31, 2021, with follow-up until August 31, 2022) and 8 Spanish hospitals (validation cohort; October 1, 1995, to August 4, 2020, with follow-up until August 16, 2022).

Exposures

Clinical evaluations at least every 6 months.

Main Outcomes and Measures

The main outcomes were 6-month confirmed disability worsening (CDW) and an Expanded Disability Status Scale (EDSS) score of 3. Levels of sNfL were measured in blood samples obtained within 12 months after disease onset using a single molecule array kit. The cutoffs used were sNfL level of 10 pg/mL and a standardized score (z score) of 1.5. Multivariable Cox proportional hazards regression models were used to evaluate outcomes.

Results

Of the 578 patients included in the study, 327 were in the development cohort (median age at sNfL analysis, 34.1 years [IQR, 27.2-42.7 years]; 226 female [69.1%]) and 251 patients were in the validation cohort (median age at sNfL analysis, 33.3 years [IQR, 27.4-41.5 years]; 184 female [73.3%]). The median follow-up was 7.10 years (IQR, 4.18-10.0 years). Levels of sNfL greater than 10 pg/mL were independently associated with higher risk of 6-month CDW and an EDSS of 3 in the development cohort (6-month CDW: hazard ratio [HR], 2.39; 95% CI, 1.39-4.12; P = .002; EDSS of 3: HR, 4.12; 95% CI, 2.18-7.77; P < .001) and the validation cohort (6-month CDW: HR, 1.61; 95% CI, 1.07-2.42; P = .02; EDSS of 3: HR, 2.03; 95% CI, 1.23-3.33; P = .005). Highly effective disease-modifying treatments were associated with lower risks of 6-month CDW and an EDSS of 3 in patients with high baseline sNfL values.

Conclusions and Relevance

This cohort study found that high sNfL values obtained within the first year of disease were associated with long-term disability worsening in MS, suggesting that sNfL level measurement may help identify optimal candidates for highly effective disease-modifying treatments.

Serum Glial Fibrillary Acidic Protein Compared With Neurofilament Light Chain as a Biomarker for Disease Progression in Multiple Sclerosis

Importance

There is a lack of validated biomarkers for disability progression independent of relapse activity (PIRA) in multiple sclerosis (MS).

Objective

To determine how serum glial fibrillary acidic protein (sGFAP) and serum neurofilament light chain (sNfL) correlate with features of disease progression vs acute focal inflammation in MS and how they can prognosticate disease progression.

Design, Setting, and Participants

Data were acquired in the longitudinal Swiss MS cohort (SMSC; a consortium of tertiary referral hospitals) from January 1, 2012, to October 20, 2022. The SMSC is a prospective, multicenter study performed in 8 centers in Switzerland. For this nested study, participants had to meet the following inclusion criteria: cohort 1, patients with MS and either stable or worsening disability and similar baseline Expanded Disability Status Scale scores with no relapses during the entire follow-up; and cohort 2, all SMSC study patients who had initiated and continued B-cell-depleting treatment (ie, ocrelizumab or rituximab).

Exposures

Patients received standard immunotherapies or were untreated.

Main Outcomes and Measures

In cohort 1, sGFAP and sNfL levels were measured longitudinally using Simoa assays. Healthy control samples served as the reference. In cohort 2, sGFAP and sNfL levels were determined cross-sectionally.

Results

This study included a total of 355 patients (103 [29.0%] in cohort 1: median [IQR] age, 42.1 [33.2-47.6] years; 73 female patients [70.9%]; and 252 [71.0%] in cohort 2: median [IQR] age, 44.3 [33.3-54.7] years; 156 female patients [61.9%]) and 259 healthy controls with a median [IQR] age of 44.3 [36.3-52.3] years and 177 female individuals (68.3%). sGFAP levels in controls increased as a function of age (1.5% per year; P < .001), were inversely correlated with BMI (-1.1% per BMI unit; P = .01), and were 14.9% higher in women than in men (P = .004). In cohort 1, patients with worsening progressive MS showed 50.9% higher sGFAP levels compared with those with stable MS after additional sNfL adjustment, whereas the 25% increase of sNfL disappeared after additional sGFAP adjustment. Higher sGFAP at baseline was associated with accelerated gray matter brain volume loss (per doubling: 0.24% per year; P < .001) but not white matter loss. sGFAP levels remained unchanged during disease exacerbations vs remission phases. In cohort 2, median (IQR) sGFAP z scores were higher in patients developing future confirmed disability worsening compared with those with stable disability (1.94 [0.36-2.23] vs 0.71 [-0.13 to 1.73]; P = .002); this was not significant for sNfL. However, the combined elevation of z scores of both biomarkers resulted in a 4- to 5-fold increased risk of confirmed disability worsening (hazard ratio [HR], 4.09; 95% CI, 2.04-8.18; P < .001) and PIRA (HR, 4.71; 95% CI, 2.05-9.77; P < .001).

Conclusions and Relevance

Results of this cohort study suggest that sGFAP is a prognostic biomarker for future PIRA and revealed its complementary potential next to sNfL. sGFAP may serve as a useful biomarker for disease progression in MS in individual patient management and drug development.

Recent Progress in the Identification of Early Transition Biomarkers from Relapsing-Remitting to Progressive Multiple Sclerosis

Despite extensive research into the pathophysiology of multiple sclerosis (MS) and recent developments in potent disease-modifying therapies (DMTs), two-thirds of relapsing-remitting MS patients transition to progressive MS (PMS). The main pathogenic mechanism in PMS is represented not by inflammation but by neurodegeneration, which leads to irreversible neurological disability. For this reason, this transition represents a critical factor for the long-term prognosis. Currently, the diagnosis of PMS can only be established retrospectively based on the progressive worsening of the disability over a period of at least 6 months. In some cases, the diagnosis of PMS is delayed for up to 3 years. With the approval of highly effective DMTs, some with proven effects on neurodegeneration, there is an urgent need for reliable biomarkers to identify this transition phase early and to select patients at a high risk of conversion to PMS. The purpose of this review is to discuss the progress made in the last decade in an attempt to find such a biomarker in the molecular field (serum and cerebrospinal fluid) between the magnetic resonance imaging parameters and optical coherence tomography measures.

Serum GFAP and NfL Levels Differentiate Subsequent Progression and Disease Activity in Patients With Progressive Multiple Sclerosis

Background and Objectives

Neurodegeneration and astrocytic activation are pathologic hallmarks of progressive multiple sclerosis (MS) and can be quantified by serum neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP). We investigated sNfL and sGFAP as tools for stratifying patients with progressive MS based on progression and disease activity status.

Methods

We leveraged our Comprehensive Longitudinal Investigation of MS at the Brigham and Women's Hospital (CLIMB) natural history study, which includes clinical, MRI data and serum samples collected over more than 20 years. We included patients with MS with a confirmed Expanded Disability Status Scale (EDSS) score ≥3 that corresponds with our classifier for patients at high risk of underlying progressive pathology. We analyzed sNfL and sGFAP within 6 months from the confirmed EDSS score ≥3 corresponding with our baseline visit. Patients who further developed 6-month confirmed disability progression (6mCDP) were classified as progressors. We further stratified our patients into active/nonactive based on new brain/spinal cord lesions or relapses in the 2 years before baseline or during follow-up. Statistical analysis on log-transformed sGFAP/sNfL assessed the baseline association with demographic, clinical, and MRI features and associations with future disability.

Results

We included 257 patients with MS who had an average EDSS score of 4.0 and a median follow-up after baseline of 7.6 years. sNfL was higher in patients with disease activity in the 2 years before baseline (adjusted β = 1.21; 95% CI 1.04–1.42;p= 0.016), during the first 2 years of follow-up (adjusted β = 1.17; 95% CI = 1.01–1.36;p= 0.042). sGFAP was not increased in the presence of disease activity. Higher sGFAP levels, but not sNfL levels, were associated with higher risk of 6mCDP (adjusted hazard ratio [HR] = 1.71; 95% CI = 1.19–2.45;p= 0.004). The association was stronger in patients with low sNfL (adjusted HR = 2.44; 95% CI 1.32–4.52;p= 0.005) and patients who were nonactive in the 2 years prior or after the sample.

Discussion

Higher levels of sGFAP correlated with subsequent progression, particularly in nonactive patients, whereas sNfL reflected acute disease activity in patients with MS at high risk of underlying progressive pathology. Thus, sGFAP and sNfL levels may be used to stratify patients with progressive MS for clinical research studies and clinical trials and may inform clinical care.

Diagnosis and treatment of progressive multiple sclerosis: A position paper

BACKGROUND AND PURPOSE

Multiple sclerosis (MS) is an unpredictable disease characterised by a highly variable disease onset and clinical course. Three main clinical phenotypes have been described. However, distinguishing between the two progressive forms of MS can be challenging for clinicians. This article examines how the diagnostic definitions of progressive MS impact clinical research, the design of clinical trials and, ultimately, treatment decisions.

METHODS

We carried out an extensive review of the literature highlighting differences in the definition of progressive forms of MS, and the importance of assessing the extent of the ongoing inflammatory component in MS when making treatment decisions.

RESULTS

Inconsistent results in phase III clinical studies of treatments for progressive MS, may be attributable to differences in patient characteristics (e.g., age, clinical and radiological activity at baseline) and endpoint definitions. In both primary and secondary progressive MS, patients who are younger and have more active disease will derive the greatest benefit from the available treatments.

CONCLUSIONS

We recommend making treatment decisions based on the individual patient's pattern of disease progression, as well as functional, clinical and imaging parameters, rather than on their clinical phenotype. Because the definition of progressive MS differs across clinical studies, careful selection of eligibility criteria and study endpoints is needed for future studies in patients with progressive MS.

Neuroaxonal and Glial Markers in Patients of the Same Age With Multiple Sclerosis

BACKGROUND AND OBJECTIVES

The specificity of novel blood biomarkers for multiple sclerosis (MS)-related neurodegeneration is unclear because neurodegeneration also occurs during normal aging. To understand which aspects of neurodegeneration the serum biomarkers neurofilament light (sNfL), serum glial fibrillary acidic protein (sGFAP), and serum contactin-1 (sCNTN1) reflect, we here explore their cross-sectional association with disability outcome measures and MRI volumes in a unique cohort of people with MS (PwMS) of the same age.

METHODS

sNfL, sGFAP (both singe-molecule array technology) and sCNTN1 (Luminex) were measured in serum samples of 288 PwMS and 125 healthy controls (HCs) of the Project Y cohort, a population-based cross-sectional study of PwMS born in the Netherlands in 1966 and age-matched HC.

RESULTS

sNfL (9.83 pg/mL [interquartile range {IQR}: 7.8-12.0]) and sGFAP (63.7 pg/mL [IQR: 48.5-84.5]) were higher in PwMS compared with HC (sNfL: 8.8 pg/mL [IQR: 7.0-10.5]; sGFAP: 51.7 pg/mL [IQR: 40.1-68.3]) (p < 0.001), whereas contactin-1 (7,461.3 pg/mL [IQR: 5,951.8-9,488.6]) did not significantly differ between PwMS compared with HC (7,891.2 pg/mL [IQR: 6,120.0-10,265.8]) (p = 0.068). sNfL and sGFAP levels were 1.2-fold higher in secondary progressive patients (SPMS) compared with relapsing remitting patients (p = 0.009 and p = 0.043). Stratified by MS subtype, no relations were seen for CNTN1, whereas sNfL and sGFAP correlated with the Expanded Disability Status Scale (ρ = 0.43 and ρ = 0.39), Nine-Hole Peg Test, Timed 25-Foot Walk Test, and Symbol Digit Modalities Test (average ρ = 0.38) only in patients with SPMS. Parallel to these clinical findings, correlations were only found for sNfL and sGFAP with MRI volumes. The strongest correlations were observed between sNfL and thalamic volume (ρ = -0.52) and between sGFAP with deep gray matter volume (ρ = - 0.56) in primary progressive patients.

DISCUSSION

In our cohort of patients of the same age, we report consistent correlations of sNfL and sGFAP with a range of metrics, especially in progressive MS, whereas contactin-1 was not related to clinical or MRI measures. This demonstrates the potential of sNfL and sGFAP as complementary biomarkers of neurodegeneration, reflected by disability, in progressive MS.

Molecular models of multiple sclerosis severity identify heterogeneity of pathogenic mechanisms

While autopsy studies identify many abnormalities in the central nervous system (CNS) of subjects dying with neurological diseases, without their quantification in living subjects across the lifespan, pathogenic processes cannot be differentiated from epiphenomena. Using machine learning (ML), we searched for likely pathogenic mechanisms of multiple sclerosis (MS). We aggregated cerebrospinal fluid (CSF) biomarkers from 1305 proteins, measured blindly in the training dataset of untreated MS patients (N = 129), into models that predict past and future speed of disability accumulation across all MS phenotypes. Healthy volunteers (N = 24) data differentiated natural aging and sex effects from MS-related mechanisms. Resulting models, validated (Rho 0.40-0.51, p < 0.0001) in an independent longitudinal cohort (N = 98), uncovered intra-individual molecular heterogeneity. While candidate pathogenic processes must be validated in successful clinical trials, measuring them in living people will enable screening drugs for desired pharmacodynamic effects. This will facilitate drug development making, it hopefully more efficient and successful.

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.

Neurofilaments contribution in clinic: state of the art

Neurological biomarkers are particularly valuable to clinicians as they can be used for diagnosis, prognosis, or response to treatment. This field of neurology has evolved considerably in recent years with the improvement of analytical methods, allowing the detection of biomarkers not only in cerebrospinal fluid (CSF) but also in less invasive fluids like blood. These advances greatly facilitate the repeated quantification of biomarkers, including at asymptomatic stages of the disease. Among the various informative biomarkers of neurological disorders, neurofilaments (NfL) have proven to be of particular interest in many contexts, such as neurodegenerative diseases, traumatic brain injury, multiple sclerosis, stroke, and cancer. Here we discuss these different pathologies and the potential value of NfL assay in the management of these patients, both for diagnosis and prognosis. We also describe the added value of NfL compared to other biomarkers currently used to monitor the diseases described in this review.

Neurofilament light chain in blood as a diagnostic and predictive biomarker for multiple sclerosis: A systematic review and meta-analysis

Background

Neurofilament light chain (NfL) in cerebrospinal fluid (CSF) is a biomarker of multiple sclerosis (MS). However, CSF sampling is invasive and has limited the clinical application. With the development of highly sensitive single-molecule assay, the accurate quantification of the very low NfL levels in blood become feasible. As evidence being accumulated, we performed a meta-analysis to evaluate the diagnostic and predictive value of blood NfL in MS patients.

Methods

We performed literature search on PubMed, EMBASE, Web of Science and Cochrane Library from inception to May 31, 2022. The blood NfL differences between MS vs. controls, MS vs. clinically isolated syndrome (CIS), progressive MS (PMS) vs. relapsing-remitting MS (RRMS), and MS in relapse vs. MS in remission were estimated by standard mean difference (SMD) and corresponding 95% confidence interval (CI). Pooled hazard ratio (HR) and 95%CI were calculated to predict time to reach Expanded Disability Status Scale (EDSS) score≥4.0 and to relapse.

Results

A total of 28 studies comprising 6545 MS patients and 2477 controls were eligible for meta-analysis of diagnosis value, and 5 studies with 4444 patients were synthesized in analysis of predictive value. Blood NfL levels were significantly higher in MS patients vs. age-matched controls (SMD = 0.64, 95%CI 0.44–0.85, P<0.001), vs. non-matched controls (SMD = 0.76, 95%CI 0.56–0.96, P<0.001) and vs. CIS patients (SMD = 0.30, 95%CI 0.18–0.42, P<0.001), in PMS vs. RRMS (SMD = 0.56, 95%CI 0.27–0.85, P<0.001), and in relapsed patients vs. remitted patients (SMD = 0.54, 95%CI 0.16–0.92, P = 0.005). Patients with high blood NfL levels had shorter time to reach EDSS score≥4.0 (HR = 2.36, 95%CI 1.32–4.21, P = 0.004) but similar time to relapse (HR = 1.32, 95%CI 0.90–1.93, P = 0.155) compared to those with low NfL levels.

Conclusion

As far as we know, this is the first meta-analysis evaluating the diagnosis and predictive value of blood NfL in MS. The present study indicates blood NfL may be a useful biomarker in diagnosing MS, distinguishing MS subtypes and predicting disease worsening in the future.

Neurofilaments in neurologic disorders and beyond

Many neurologic diseases can initially present as a diagnostic challenge and even when a diagnosis is made, monitoring of disease activity, progression and response to therapy may be limited with existing clinical and paraclinical assessments. As such, the identification of disease specific biomarkers provides a promising avenue by which diseases can be effectively diagnosed, monitored and used as a prognostic indicator for long-term outcomes. Neurofilaments are an integral component of the neuronal cytoskeleton, where assessment of neurofilaments in the blood, cerebrospinal fluid (CSF) and diseased tissue has been shown to have value in providing diagnostic clarity, monitoring disease activity, tracking progression and treatment efficacy, as well as lending prognostic insight into long-term outcomes. As such, this review attempts to provide a glimpse into the structure and function of neurofilaments, their role in various neurologic and non-neurologic disorders, including uncommon conditions with recent knowledge of neurofilament-related pathology, as well as their applicability in future clinical practice.

Focus on the Role of the NLRP3 Inflammasome in Multiple Sclerosis: Pathogenesis, Diagnosis, and Therapeutics

Neuroinflammation is initiated with an aberrant innate immune response in the central nervous system (CNS) and is involved in many neurological diseases. Inflammasomes are intracellular multiprotein complexes that can be used as platforms to induce the maturation and secretion of proinflammatory cytokines and pyroptosis, thus playing a pivotal role in neuroinflammation. Among the inflammasomes, the nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3 (NLRP3) inflammasome is well-characterized and contributes to many neurological diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD), and ischemic stroke. MS is a chronic autoimmune disease of the CNS, and its hallmarks include chronic inflammation, demyelination, and neurodegeneration. Studies have demonstrated a relationship between MS and the NLRP3 inflammasome. To date, the pathogenesis of MS is not fully understood, and clinical studies on novel therapies are still underway. Here, we review the activation mechanism of the NLRP3 inflammasome, its role in MS, and therapies targeting related molecules, which may be beneficial in MS.

Plasma glial fibrillary acidic protein and neurofilament light chain in relation to disability worsening in multiple sclerosis

Background:

Predicting disability worsening in multiple sclerosis (MS) remains an important challenge. Glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) seem promising biomarkers. Studies investigating blood GFAP in relation to longitudinal outcome measures in MS are scarce.

Objective:

To compare plasma-GFAP (p-GFAP) and plasma-NfL (p-NfL) levels in relation to sustained disability worsening.

Methods:

We measured baseline p-GFAP and p-NfL in a prospective cohort of 115 individuals with MS and 30 matched controls, using Single Molecule Array (Simoa). Disability worsening was defined as an increase in at least one of three measures (Expanded Disability Status Scale, Timed 25-foot walk, 9-Hole Peg test), confirmed after 6 months and persistent upon data closure.

Results:

In a multivariable Cox proportional-hazards model, p-GFAP was not significantly associated with sustained disability worsening after 4.40 ± 0.82 years, while p-NfL (HR = 1.046, p = 0.001), EDSS (HR = 1.24, p = 0.039), and disease duration (HR = 1.048, p = 0.017) were. Area under the curve of ROC curves in relation to worsening was 0.61 for p-GFAP ( p = 0.031) and 0.63 for p-NfL ( p = 0.015). Kaplan–Meier curves showed similar patterns for both proteins.

Conclusion:

p-NfL emerged as a significant explanatory variable for worsening in Cox regression analysis, and p-GFAP did not. Both p-GFAP and p-NfL were related to worsening based on ROC curves.

Serum-Based Biomarkers in Neurodegeneration and Multiple Sclerosis

Multiple Sclerosis (MS) is a debilitating disease with typical onset between 20 and 40 years of age, so the disability associated with this disease, unfortunately, occurs in the prime of life. At a very early stage of MS, the relapsing-remitting mobility impairment occurs in parallel with a progressive decline in cognition, which is subclinical. This stage of the disease is considered the beginning of progressive MS. Understanding where a patient is along such a subclinical phase could be critical for therapeutic efficacy and enrollment in clinical trials to test drugs targeted at neurodegeneration. Since the disease course is uneven among patients, biomarkers are needed to provide insights into pathogenesis, diagnosis, and prognosis of events that affect neurons during this subclinical phase that shapes neurodegeneration and disability. Thus, subclinical cognitive decline must be better understood. One approach to this problem is to follow known biomarkers of neurodegeneration over time. These biomarkers include Neurofilament, Tau and phosphotau protein, amyloid-peptide-β, Brl2 and Brl2-23, N-Acetylaspartate, and 14-3-3 family proteins. A composite set of these serum-based biomarkers of neurodegeneration might provide a distinct signature in early vs. late subclinical cognitive decline, thus offering additional diagnostic criteria for progressive neurodegeneration and response to treatment. Studies on serum-based biomarkers are described together with selective studies on CSF-based biomarkers and MRI-based biomarkers.

Smoking Attributable Risk in Multiple Sclerosis

Tobacco smoke is an important modifiable environmental risk factor for multiple sclerosis (MS) risk. The population attributable fraction (AF) of MS due to smoking can be used to assess the contribution of smoking to the risk of MS development. We conducted a matched case-control study, including individuals with MS and population-based controls. Overall, sex- and genetic risk score-stratified AF due to smoking were calculated by fitting logistic regression models. We included 9,419 individuals with MS and 9,419 population-based matched controls. At the time of MS onset 44.1% of persons with MS and 35.9% of controls ever regularly smoked of which 38.1% and 29.2% were still smoking. The overall AF was 13.1% (95%CI: 10.7 to 15.4). The AF was 10.6% (95%CI: 7.4 to 13.7) in females and 19.1% (95%CI: 13.1 to 25.1) in males. The AF was 0.6% (95%CI: 0.0 to 2) in ex-smokers. In those having human leucocyte antigen (HLA) and non-HLA risk scores above the median levels of controls, the AF was 11.4% (95%CI: 6.8 to 15.9) and 12% (95%CI: 7.7 to 16.3), respectively. The AF was 17.6% (95%CI: 10.2 to 24.9) and 18.6% (95%CI: 5.5 to 31.6) in those with HLA and non-HLA risk scores below the median levels in controls, respectively. We noticed a decline in AF in recent birth cohorts. This study indicates that at least 13% of cases of MS could be prevented through the avoidance of tobacco smoking. Considering the prevalence of MS, this represents a very large group of people in absolute number.

SARS-CoV-2 and Multiple Sclerosis: Potential for Disease Exacerbation

While the respiratory tract is the primary route of entry for SARS-CoV-2, evidence shows that the virus also impacts the central nervous system. Intriguingly, case reports have documented SARS-CoV-2 patients presenting with demyelinating lesions in the brain, spinal cord, and optic nerve, suggesting possible implications in neuroimmune disorders such as multiple sclerosis (MS) and other related neuroimmune disorders. However, the cellular mechanisms underpinning these observations remain poorly defined. The goal of this paper was to review the literature to date regarding possible links between SARS-CoV-2 infection and neuroimmune demyelinating diseases such as MS and its related disorders, with the aim of positing a hypothesis for disease exacerbation. The literature suggests that SARS-CoV, SARS-CoV-2, and orthologous murine coronaviruses invade the CNS via the olfactory bulb, spreading to connected structures via retrograde transport. We hypothesize that a glial inflammatory response may contribute to damaged oligodendrocytes and blood brain barrier (BBB) breakdown, allowing a second route for CNS invasion and lymphocyte infiltration. Potential for molecular mimicry and the stimulation of autoreactive T cells against myelin is also described. It is imperative that further studies on SARS-CoV-2 neuroinvasion address the adverse effects of the virus on myelin and exacerbation of MS symptoms, as nearly 3 million people suffer from MS worldwide.

Blood Neurofilament Light in Progressive Multiple Sclerosis: Post Hoc Analysis of 2 Randomized Controlled Trials

OBJECTIVE

To investigate the potential of plasma neurofilament light (pNfL) as a biomarker of disease progression and treatment response in progressive multiple sclerosis (PMS) with and without acute disease activity.

METHODS

Post hoc blinded analysis of pNfL levels in two placebo-controlled, phase 3 studies in secondary progressive MS (SPMS; EXPAND) and primary progressive MS (PPMS; INFORMS) using siponimod and fingolimod, respectively, as active compounds. pNfL levels were quantified using a single molecule array ("Homebrew" Simoa) immunoassay from stored EDTA plasma samples of all patients who consented for exploratory biomarker analysis in either study; pNfL levels were divided into high (≥30 pg/mL) and low (<30 pg/mL) at baseline (BL). We investigated the association of pNfL levels with disability progression, cognitive decline and brain atrophy, and their sensitivity to indicate treatment response vis-à-vis clinical measures.

RESULTS

We analyzed pNfL in 4185 samples from 1452 SPMS patients and 1172 samples from 378 PPMS patients. BL pNfL levels were higher in SPMS (geomean 32.1pg/mL) than in PPMS (22.0pg/mL; p<0.0001) patients. In both studies, higher BL pNfL levels were associated with older age, higher EDSS score, more Gd⁺ lesions, and higher T2 lesion load (all p<0.05). Independent of treatment, high versus low BL pNfL levels were associated with significantly higher risks of confirmed 3-month (SPMS [32%], HR [95%CI]: 1.32 [1.09;1.61]; PPMS [49%], 1.49 [1.05;2.12]) and 6-month disability progression (SPMS [26%], 1.26 [1.01;1.57]; PPMS [48%], 1.48 [1.01;2.17]), earlier wheelchair dependence (SPMS [50%], 1.50 [0.96;2.34]; PPMS [197%], 2.97 [1.44;6.10]), cognitive decline (SPMS [41%], 1.41 [1.09;1.84]) and higher rates of brain atrophy (mean change at month [M]24: SPMS, -0.92; PPMS, -1.39). BL pNfL levels were associated with future disability progression and the degree of brain atrophy regardless of presence or absence of acute disease activity (gadolinium-enhancing lesions or recent occurrence of relapses before BL). pNfL levels were lower in patients treated with siponimod or fingolimod versus placebo-treated patients and higher in those having experienced disability progression.

CONCLUSION

pNfL was associated with future clinical and radiological disability progression features at the group level. pNfL was reduced by treatment and may be a meaningful outcome measure in PMS studies.

Development of an age-adjusted model for blood neurofilament light chain

OBJECTIVE

To develop an age-adjustment model for neurofilament light chain (NfL), an emerging injury marker in patients with a range of neurologic conditions including multiple sclerosis (MS).

METHODS

Serum and plasma samples were collected from a healthy donor (HD) cohort of 118 individuals aged 24 to 66 years, 90 patients with relapsing MS (RMS) and 22 patients with progressive MS (PMS). Serum and plasma samples were assessed for NfL using the SIMOA assay (Quanterix NfL Advantage Kit™). A log-linear model was used to evaluate the relationship between NfL and age and to calculate age-adjusted NfL levels.

RESULTS

Higher serum and plasma NfL levels were significantly associated with increasing HD age. Log-transformation of blood NfL levels reduced heteroscedasticity and skewness. A log-linear model enabled adjustment for age-related increase in serum and plasma NfL levels (2.3% [95% CI, 1.6-2.9] and 2.6% [95% CI, 1.3-3.3] per year, respectively). Following age adjustment, NfL did not show significant association with HD sex or ethnicity. While unadjusted serum NfL levels were elevated in patients with PMS (mean age 56 years) compared with those with RMS (mean age 37 years), age-adjusted NfL levels did not differ.

INTERPRETATION

A log-linear, age adjustment model was developed to enable comparison of NfL levels across populations with different ages. While additional data and evidence are needed for patient-level adoption, this could be a valuable tool for interpreting NfL levels across a range of patient groups with neurologic conditions.

Correlation between cerebrospinal fluid and plasma neurofilament light protein in treated HIV infection: results from the COBRA study

Cerebrospinal fluid (CSF) neurofilament light protein (NfL) is a marker of central nervous system neuro-axonal injury. A novel, ultra-sensitive assay can determine plasma NfL. In untreated people-with-HIV (PWH), CSF and plasma NfL are strongly correlated. We aimed to assess this correlation in PWH on suppressive antiretroviral treatment (ART) and lifestyle-similar HIV-negative individuals enrolled into the COmorBidity in Relation to AIDS (COBRA) study. Differences in paired CSF (sandwich ELISA, UmanDiagnostics) and plasma (Simoa digital immunoassay, Quanterix™) NfL between PWH and HIV-negative participants were tested using Wilcoxon's test; associations were assessed using Pearson's correlation. CSF and plasma NfL, standardised to Z-scores, were included as dependent variables in linear regression models to identify factors independently associated with values in PWH and HIV-negative participants. Overall, 132 PWH (all with plasma HIV RNA < 50 copies/mL) and 79 HIV-negative participants were included. Neither CSF (median 570 vs 568 pg/mL, p = 0.37) nor plasma (median 10.7 vs 9.9 pg/mL, p = 0.15) NfL differed significantly between PWH and HIV-negative participants, respectively. CSF and plasma NfL correlated moderately, with no significant difference by HIV status (PWH: rho = 0.52; HIV-negative participants: rho = 0.47, p (interaction) = 0.63). In multivariable regression analysis, higher CSF NfL Z-score was statistically significantly associated with older age and higher CSF protein, and higher plasma NfL Z-score with older age, higher serum creatinine and lower bodyweight. In conclusion, in PWH on ART, the correlation between CSF and plasma NfL is moderate and similar to that observed in lifestyle-similar HIV-negative individuals. Consideration of renal function and bodyweight may be required when utilising plasma NfL.

Iron Rims in Patients With Multiple Sclerosis as Neurodegenerative Marker? A 7-Tesla Magnetic Resonance Study

Introduction: Multiple sclerosis (MS) is a demyelinating and neurodegenerative disease of the central nervous system, characterized by inflammatory-driven demyelination. Symptoms in MS manifest as both physical and neuropsychological deficits. With time, inflammation is accompanied by neurodegeneration, indicated by brain volume loss on an MRI. Here, we combined clinical, imaging, and serum biomarkers in patients with iron rim lesions (IRLs), which lead to severe tissue destruction and thus contribute to the accumulation of clinical disability.

Objectives: Subcortical atrophy and ventricular enlargement using an automatic segmentation pipeline for 7 Tesla (T) MRI, serum neurofilament light chain (sNfL) levels, and neuropsychological performance in patients with MS with IRLs and non-IRLs were assessed.

Methods: In total 29 patients with MS [15 women, 24 relapsing-remitting multiple sclerosis (RRMS), and five secondary-progressive multiple sclerosis (SPMS)] aged 38 (22–69) years with an Expanded Disability Status Score of 2 (0–8) and a disease duration of 11 (5–40) years underwent neurological and neuropsychological examinations. Volumes of lesions, subcortical structures, and lateral ventricles on 7-T MRI (SWI, FLAIR, and MP2RAGE, 3D Segmentation Software) and sNfL concentrations using the Simoa SR-X Analyzer in IRL and non-IRL patients were assessed.

Results: (1) Iron rim lesions patients had a higher FLAIR lesion count (p = 0.047). Patients with higher MP2Rage lesion volume exhibited more IRLs (p <0.014) and showed poorer performance in the information processing speed tested within 1 year using the Symbol Digit Modalities Test (SDMT) (p <0.047). (2) Within 3 years, patients showed atrophy of the thalamus (p = 0.021) and putamen (p = 0.043) and enlargement of the lateral ventricles (p = 0.012). At baseline and after 3 years, thalamic volumes were lower in IRLs than in non-IRL patients (p = 0.045). (3) At baseline, IRL patients had higher sNfL concentrations (p = 0.028). Higher sNfL concentrations were associated with poorer SDMT (p = 0.004), regardless of IRL presence. (4) IRL and non-IRL patients showed no significant difference in the neuropsychological performance within 1 year.

Conclusions: Compared with non-IRL patients, IRL patients had higher FLAIR lesion counts, smaller thalamic volumes, and higher sNfL concentrations. Our pilot study combines IRL and sNfL, two biomarkers considered indicative for neurodegenerative processes. Our preliminary data underscore the reported destructive nature of IRLs.

Charting a global research strategy for progressive MS-An international progressive MS Alliance proposal

BACKGROUND

Progressive forms of multiple sclerosis (MS) affect more than 1 million individuals globally. Recent approvals of ocrelizumab for primary progressive MS and siponimod for active secondary progressive MS have opened the therapeutic door, though results from early trials of neuroprotective agents have been mixed. The recent introduction of the term 'active' secondary progressive MS into the therapeutic lexicon has introduced potential confusion to disease description and thereby clinical management.

OBJECTIVE

This paper reviews recent progress, highlights continued knowledge and proposes, on behalf of the International Progressive MS Alliance, a global research strategy for progressive MS.

METHODS

Literature searches of PubMed between 2015 and May, 2021 were conducted using the search terms "progressive multiple sclerosis", "primary progressive multiple sclerosis", "secondary progressive MS". Proposed strategies were developed through a series of in-person and virtual meetings of the International Progressive MS Alliance Scientific Steering Committee.

RESULTS

Sustaining and accelerating progress will require greater understanding of underlying mechanisms, identification of potential therapeutic targets, biomarker discovery and validation, and conduct of clinical trials with improved trial design. Encouraging developments in symptomatic and rehabilitative interventions are starting to address ongoing challenges experienced by people with progressive MS.

CONCLUSION

We need to manage these challenges and realise the opportunities in the context of a global research strategy, which will improve quality of life for people with progressive MS.

Serum Neurofilament Light Association With Progression in Natalizumab-Treated Patients With Relapsing-Remitting Multiple Sclerosis

BACKGROUND AND OBJECTIVES

To investigate the potential of serum neurofilament light (NfL) to reflect or predict progression mostly independent of acute inflammatory disease activity in patients with relapsing-remitting multiple sclerosis (RRMS) treated with natalizumab.

METHODS

Patients were selected from a prospective observational cohort study initiated in 2006 at the VU University Medical Center Amsterdam, the Netherlands, including patients with RRMS treated with natalizumab. Selection criteria included an age of 18 years or older and a minimum follow-up of 3 years from natalizumab initiation. Clinical and MRI assessments were performed on a yearly basis, and serum NfL was measured at 5 time points during the follow-up, including on the day of natalizumab initiation (baseline), 3 months, 1 year, and 2 years after natalizumab initiation, and on last follow-up visit. Using general linear regression models, we compared the longitudinal dynamics of NfL between patients with and without confirmed Expanded Disability Status Scale (EDSS) progression between year 1 visit and last follow-up, and between individuals with and without EDSS⁺ progression, a composite endpoint including the EDSS, 9-hole peg test, and timed 25-foot walk.

RESULTS

Eighty-nine natalizumab-treated patients with RRMS were included. Median follow-up time was 5.2 years (interquartile range [IQR] 4.3-6.7, range 3.0-11.0) after natalizumab initiation, mean age at time of natalizumab initiation was 36.9 years (SD 8.5), and median disease duration was 7.4 years (IQR 3.8-12.1). Between year 1 and the last follow-up, 28/89 (31.5%) individuals showed confirmed EDSS progression. Data for the EDSS⁺ endpoint was available for 73 out of the 89 patients and 35/73 (47.9%) showed confirmed EDSS⁺ progression. We observed a significant reduction in NfL levels 3 months after natalizumab initiation, which reached its nadir of close to 50% of baseline levels 1 year after treatment initiation. We found no difference in the longitudinal dynamics of NfL in progressors vs nonprogressors. NfL levels at baseline and 1 year after natalizumab initiation did not predict progression at last follow-up.

CONCLUSION

In our cohort of natalizumab-treated patients with RRMS, NfL fails to capture or predict progression that occurs largely independently of clinical or radiologic signs of acute focal inflammatory disease activity. Additional biomarkers may thus be needed to monitor progression in these patients.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that serum NfL levels are not associated with disease progression in natalizumab-treated patients with RRMS.

Prediagnostic Neurofilament Light Chain Levels in Amyotrophic Lateral Sclerosis

BACKGROUND AND OBJECTIVES

To assess whether plasma neurofilament light chain (NfL) levels are elevated before amyotrophic lateral sclerosis (ALS) diagnosis and to evaluate whether prediagnostic NfL levels are associated with metabolic alterations.

METHODS

We conducted a matched case-control study nested in 3 large prospective US cohorts (the Nurses' Health Study, the Health Professionals Follow-up Study, and the Multiethnic Cohort Study) and identified 84 individuals who developed ALS during follow-up and had available plasma samples prior to disease diagnosis. For each ALS case, we randomly selected controls from those who were alive at the time of the case diagnosis and matched on birth year, sex, race/ethnicity, fasting status, cohort, and time of blood draw. We measured NfL in the plasma samples and used conditional logistic regression to estimate rate ratios (RRs) and 95% confidence intervals (CIs) for ALS, adjusting for body mass index, smoking, physical activity, and urate levels.

RESULTS

Higher NfL levels were associated with a higher ALS risk in plasma samples collected within 5 years of the ALS diagnosis (RR per 1 SD increase 2.68, 95% CI 1.18-6.08), but not in samples collected further away from the diagnosis (RR per 1 SD increase 1.16, 95% CI 0.78-1.73). A total of 21 metabolites were correlated with prediagnostic NfL levels in ALS cases (p < 0.05), but none of these remained significant after multiple comparison adjustments.

DISCUSSION

Plasma NfL levels were elevated in prediagnostic ALS cases, indicating that NfL may be a useful biomarker already in the earliest stages of the disease.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that plasma NfL levels are elevated in prediagnostic ALS.

Neurofilament light chain as a biomarker for diagnosis of multiple sclerosis

The treatments for multiple sclerosis (MS) have improved over the past 25 years, but now the main question for physicians is deciding who should receive treatment, for how long, and when to switch to other options. These decisions are typically based on treatment tolerance and a reasonable expectation of long-term efficacy. A significant unmet need is the lack of accurate laboratory measurements for diagnosis, and monitoring of treatment response, including deterioration and disease progression. There are few validated biomarkers for MS, and in practice, physicians employ two biomarkers discovered fifty years ago for MS diagnosis, often in combination with MRI scans. These biomarkers are intrathecal IgG and oligoclonal bands in the CSF (cerebrospinal fluid). Neurofilament light chain (NfL) is a relatively new biomarker for MS diagnosis and follow up. Neurofilaments are neuron-specific cytoskeleton proteins that can be measured in various body compartments. NfL is a new biomarker for MS that can be measured in serum samples, but this still needs further study to specify the laboratory cut-off values in clinical practice. In the present review we discuss the evidence for NfL as a reliable biomarker for the early detection and management of MS. Moreover, we highlight the correlation between MRI and NfL, and ask whether they can be combined.

NfL predicts relapse-free progression in a longitudinal multiple sclerosis cohort study

Background

Easily accessible biomarkers enabling the identification of those patients with multiple sclerosis (MS) who will accumulate irreversible disability in the long term are essential to guide early therapeutic decisions. We here examine the utility of serum neurofilament light chain (sNfL) for forecasting relapse-free disability progression and conversion to secondary progressive MS (SPMS) in the prospective Neurofilamentandlongtermoutcome inMS (NaloMS) cohort.

Methods

The predictive ability of sNfL at Baseline and sNfL follow-up (FU)/ Baseline (BL) ratio with regard to disability progression was assessed within a development cohort (NaloMS, n=196 patients with relapsing-remitting MS (RRMS) or clinically isolated syndrome) and validated with an external independent cohort (Düsseldorf, Essen, n=204). Both relapse-free EDSS-progression (RFP: inflammatory-independent EDSS-increase 12 months prior to FU) and SPMS-transition (minimum EDSS-score of 3.0) were investigated.

Findings

During the study period, 17% (n=34) of NaloMS patients suffered from RFP and 14% (n=27) converted to SPMS at FU (validation cohort RFP n=42, SPMS-conversion n=24). sNfL at BL was increased in patients with RFP (10.8 pg/ml (interquartile range (IQR) 7.7-15.0) vs. 7.2 pg/ml (4.5-12.5), p<0.017). In a multivariable logistic regression model, increased sNfL levels at BL (Odds Ratio (OR) 1.02, 95% confidence interval (CI) 1.01-1.04, p=0.012) remained an independent risk factor for RFP and predicted individual RFP risk with an accuracy of 82% (NaloMS) and 83% (validation cohort) as revealed by support vector machine. In addition, the sNfL FU/BL ratio was increased in SPMS-converters (1.16 (0.89-1.70) vs. 0.96 (0.75-1.23), p=0.011). This was confirmed by a multivariable logistic regression model, as sNfL FU/BL ratio remained in the model (OR 1.476, 95%CI 1.078-2,019, p=0.015) and individual sNfL FU/BL ratios showed a predictive accuracy of 72% in NaloMS (63% in the validation cohort) as revealed by machine learning.

Interpretation

sNfL levels at baseline predict relapse-free disability progression in a prospective longitudinal cohort study 6 years later. While prediction was confirmed in an independent cohort, sNfL further discriminates patients with SPMS at follow-up and supports early identification of patients at risk for later SPMS conversion.

Funding

This work was supported by the German Research Council (CRC-TR-128), Else Kröner Fresenius Foundation and Hertie-Stiftung.

Exploring CSF neurofilament light as a biomarker for MS in clinical practice; a retrospective registry-based study

Background:

Neurofilament light (NFL) has been increasingly recognized for prognostic and therapeutic decisions.

Objective:

To validate the utility of cerebrospinal fluid NFL (cNFL) as a biomarker in clinical practice of relapsing-remitting multiple sclerosis (RRMS).

Methods:

RRMS patients (n = 757) who had cNFL analyzed as part of the diagnostic work-up in a single academic multiple sclerosis (MS) center, 2001–2018, were retrospectively identified. cNFL concentrations were determined with two different immunoassays and the ratio of means between them was used for normalization.

Results:

RRMS with relapse had 4.4 times higher median cNFL concentration (1134 [interquartile range (IQR) 499–2744] ng/L) than those without relapse (264 [125–537] ng/L, p < 0.001) and patients with gadolinium-enhancing lesions had 3.3 times higher median NFL (1414 [606.8–3210] ng/L) than those without (426 [IQR 221–851] ng/L, p < 0.001). The sensitivity and specificity of cNFL to detect disease activity was 75% and 98.5%, respectively. High cNFL at MS onset predicted progression to Expanded Disability Status Scale (EDSS) ⩾ 3 (p < 0.001, hazard ratios (HR) = 1.89, 95% CI = 1.44–2.65) and conversion to secondary progressive MS (SPMS, p = 0.001, HR = 2.5, 95% CI = 1.4–4.2).

Conclusions:

cNFL is a robust and reliable biomarker of disease activity, treatment response, and prediction of disability and conversion from RRMS to SPMS. Our data suggest that cNFL should be included in the assessment of patients at MS-onset.

Plasma neurofilament light chain concentrations as a biomarker of clinical and radiologic outcomes in relapsing multiple sclerosis: Post hoc analysis of Phase 3 ozanimod trials

Background and purpose

We investigated plasma neurofilament light chain concentration (pNfL) as a biomarker for neuroaxonal damage and disease activity using data from Phase 3 trials of ozanimod in relapsing multiple sclerosis (RMS).

Methods

pNfL was measured before and after ozanimod 0.46 mg or 0.92 mg daily or interferon β‐1a 30 µg weekly in the randomized, double‐blind SUNBEAM and RADIANCE trials. In these post hoc analyses, we investigated relationships between pNfL (at baseline and median percentage change from baseline to Month 12 [SUNBEAM] or 24 [RADIANCE]) and clinical and magnetic resonance imaging outcomes.

Results

Median (Q1, Q3) baseline pNfL, available in 1244 of 1346 SUNBEAM participants, was 14.70 (10.16, 23.26) pg/ml and in 1109 of 1313 RADIANCE participants was 13.35 (9.42, 20.41) pg/ml. Baseline gadolinium‐enhancing (GdE) and T2 lesion counts increased and brain volume decreased with increasing baseline pNfL. Baseline pNfL was higher in those with versus without on‐treatment relapse. Median percentage reduction in pNfL at 12 months in SUNBEAM (n = 1238) and 24 months in RADIANCE (n = 1088) was greater for ozanimod (20%–27%) than interferon β‐1a (13%–16%; p < 0.01). Greater pNfL reduction was associated with fewer GdE lesions, fewer new/enlarging T2 lesions per scan, less loss of brain volume, lower annualized relapse rate (ARR), and no evidence of disease activity. The following models predicted ARR: 0.5111 + 0.0116 × ΔNfL at 12 months (SUNBEAM) and 0.4079 + 0.0088 × ΔNfL at 24 months (RADIANCE).

Conclusions

pNfL was associated with clinical and radiologic measures of disease and treatment effects in RMS, supporting its use as a biomarker.

The blood biomarkers puzzle - A review of protein biomarkers in neurodegenerative diseases

Neurodegenerative diseases are heterogeneous in their cause and clinical presentation making clinical assessment and disease monitoring challenging. Because of this, there is an urgent need for objective tools such as fluid biomarkers able to quantitate different aspects of the disease. In the last decade, technological improvements and awareness of the importance of biorepositories led to the discovery of an evolving number of fluid biomarkers covering the main characteristics of neurodegenerative diseases such as neurodegeneration, protein aggregates and inflammation. The ability to quantitate each aspect of the disease at a high definition enables a more precise stratification of the patients at inclusion in clinical trials, hence reducing the noise that may hamper the detection of therapeutical efficacy and allowing for smaller but likewise powered studies, which particularly improves the ability to start clinical trials for rare neurological diseases. Moreover, the use of fluid biomarkers has the potential to support a targeted therapeutical intervention, as it is now emerging for the treatment of amyloid-beta deposition in patients suffering from Alzheimer's disease. Here we review the knowledge that evolved from the measurement of fluid biomarker proteins in neurodegenerative conditions.

Disease biomarkers in multiple sclerosis: current serum neurofilament light chain perspectives

The continuous neuroinflammatory and neurodegenerative pathology in multiple sclerosis (MS) results in irreversible accumulation of physical and cognitive disability. Reliable early detection of MS disease processes can aid in the diagnosis, monitoring and treatment management of MS patients. Recent assay technological advancements now allow reliable quantification of serum-based neurofilament light chain (sNfL) levels, which provide temporal information regarding the degree of neuroaxonal damage. The relationship and predictive value of sNfL with clinical and cognitive outcomes, other paraclinical measures and treatment response is reviewed. sNfL measurement is an emerging, noninvasive and disease-responsive MS biomarker that is currently utilized in research and clinical trial settings. Understanding sNfL confounders and further assay standardization will allow clinical implementation of this biomarker.