Reference interval and preanalytical properties of serum neurofilament light chain in Scandinavian adults

Serum glial fibrillary acidic protein and neurofilament light chain in patients with early treated phenylketonuria

To pave the way for healthy aging in early treated phenylketonuria (ETPKU) patients, a better understanding of the neurological course in this population is needed, requiring easy accessible biomarkers to monitor neurological disease progression in large cohorts. The objective of this pilot study was to investigate the potential of glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) as blood biomarkers to indicate changes of the central nervous system in ETPKU. In this single-center cross-sectional study, GFAP and NfL concentrations in serum were quantified using the Simoa^® multiplex technology in 56 ETPKU patients aged 6–36 years and 16 age matched healthy controls. Correlation analysis and hierarchical linear regression analysis were performed to investigate an association with disease-related biochemical parameters and retinal layers assessed by optical coherence tomography. ETPKU patients did not show significantly higher GFAP concentrations (mean 73 pg/ml) compared to healthy controls (mean 60 pg/ml, p = 0.140). However, individual pediatric and adult ETPKU patients had GFAP concentrations above the healthy control range. In addition, there was a significant association of GFAP concentrations with current plasma tyrosine concentrations (r = −0.482, p = 0.036), a biochemical marker in phenylketonuria, and the retinal inner nuclear layer volume (r = 0.451, p = 0.04). There was no evidence of NfL alterations in our ETPKU cohort. These pilot results encourage multicenter longitudinal studies to further investigate serum GFAP as a complementary tool to better understand and monitor neurological disease progression in ETPKU. Follow-up investigations on aging ETPKU patients are required to elucidate the potential of serum NfL as biomarker.

Serum GFAP - reference interval and preanalytical properties in Danish adults

OBJECTIVES

Glial fibrillary acidic protein (GFAP) is a promising biomarker that could potentially contribute to diagnosis and prognosis in neurological diseases. The biomarker is approaching clinical use but the reference interval for serum GFAP remains to be established, and knowledge about the effect of preanalytical factors is also limited.

METHODS

Serum samples from 371 apparently healthy reference subjects, 21-90 years of age, were measured by a single-molecule array (Simoa) assay. Continuous reference intervals were modelled using non-parametric quantile regression and compared with traditional age-partitioned non-parametric reference intervals established according to the Clinical and Laboratory Standards Institute (CLSI) guideline C28-A3. The following preanalytical conditions were also examined: stability in whole blood at room temperature (RT), stability in serum at RT and -20 °C, repeated freeze-thaw cycles, and haemolysis.

RESULTS

The continuous reference interval showed good overall agreement with the traditional age-partitioned reference intervals of 25-136 ng/L, 34-242 ng/L, and 5-438 ng/L for the age groups 20-39, 40-64, and 65-90 years, respectively. Both types of reference intervals showed increasing levels and variability of serum GFAP with age. In the preanalytical tests, the mean changes from baseline were 2.3% (95% CI: -2.4%, 6.9%) in whole blood after 9 h at RT, 3.1% (95% CI: -4.5%, 10.7%) in serum after 7 days at RT, 10.4% (95% CI: -6.0%, 26.8%) in serum after 133 days at -20 °C, and 10.4% (95% CI: 9.5%, 11.4%) after three freeze-thaw cycles.

CONCLUSIONS

The study establishes age-dependent reference ranges for serum GFAP in adults and demonstrates overall good stability of the biomarker.

Short-term biological variation of serum glial fibrillary acidic protein

OBJECTIVES

Serum glial fibrillary acidic protein (GFAP) is an emerging biomarker for intracerebral diseases and is approved for clinical use in traumatic brain injury. GFAP is also being investigated for several other applications, where the GFAP changes are not always outstanding. It is thus essential for the interpretation of GFAP to distinguish clinical relevant changes from natural occurring biological variation. This study aimed at estimating the biological variation of serum GFAP.

METHODS

Apparently healthy subjects (n=33) had blood sampled for three consecutive days. On the second day, blood was also drawn every third hour from 9 AM to 9 PM. Serum GFAP was measured by Single Molecule Array (Simoa™). Components of biological variation were estimated in a linear mixed-effects model.

RESULTS

The overall median GFAP value was 92.5 pg/mL (range 34.4-260.3 pg/mL). The overall within- (CV_I) and between-subject variations (CV_G) were 9.7 and 39.5%. The reference change value was 36.9% for an increase. No day-to-day variation was observed, however semidiurnal variation was observed with increasing GFAP values between 9 AM and 12 PM (p<0.00001) and decreasing from 12 to 9 PM (p<0.001).

CONCLUSIONS

Serum GFAP exhibits a relatively low CV_I but a considerable CV_G and a marked semidiurnal variation. This implies caution on the timing of blood sampling and when interpreting GFAP in relation to reference intervals, especially in conditions where only small GFAP differences are observed.

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

The recent development of assays that accurately quantify neurofilament light, a neuronal cytoskeleton protein, in plasma has generated a vast literature supporting that it is a sensitive, dynamic, and robust biomarker of neuroaxonal damage. As a result, efforts are now made to introduce plasma neurofilament light into clinical routine practice, making it an easily accessible complement to its cerebrospinal fluid counterpart. An increasing literature supports the use of plasma neurofilament light in differentiating neurodegenerative diseases from their non-neurodegenerative mimics and suggests it is a valuable biomarker for the evaluation of the effect of putative disease-modifying treatments (e.g. in multiple sclerosis). More contexts of use will likely emerge over the coming years. However, to assist clinical interpretation of laboratory test values, it is crucial to establish normal reference intervals. In this study, we sought to derive reliable cut-offs by pooling quantified plasma neurofilament light in neurologically healthy participants (5–90 years) from eight cohorts. A strong relationship between age and plasma neurofilament light prompted us to define the following age-partitioned reference limits (upper 95th percentile in each age category): 5–17 years = 7 pg/mL; 18–50 years = 10 pg/mL; 51–60 years = 15 pg/mL; 61–70 years = 20 pg/mL; 70 + years = 35 pg/mL. The established reference limits across the lifespan will aid the introduction of plasma neurofilament light into clinical routine, and thereby contribute to diagnostics and disease-monitoring in neurological practice.

Serum Phosphorylated Neurofilament Heavy subunit levels and its association with the Risk for Catastrophic Injury in Thoroughbred Racehorses

Neurofilaments are structural proteins that are concentrated in the body and axons of neurons. Damage to the neurons or axons as a result of trauma or infectious diseases leads to the release of neurofilaments into blood and cerebrospinal fluid (CSF). This case-control study was carried out to compare serum levels of phosphorylated neurofilament heavy chain (pNF-H) between clinically healthy Thoroughbred (TB) horses and TB horses that suffered catastrophic musculoskeletal injuries (cMSI), and to investigate the correlation between putative risk factors and serum concentrations of pNF-H in injured horses. Blood samples were collected from clinically healthy horses and from horses that suffered cMSI. The concentration of pNF-H in serum samples was determined using the Phosphorylated Neurofilament H Sandwich enzyme-linked immunosorbent assay kit. A total of 343 horses were enrolled in the study (148 cases and 195 controls). The median serum concentration of pNF-H for controls was 0.0 ng/ml and for cases was 0.07 ng/ml. No significant difference was observed between the two groups in racing. The number of lifetime starts was correlated with serum pNF-H concentration in case horses. The serum concentration of pNF-H was higher in case horses that experienced cMSI while training than while racing. The number of lifetime starts is a proxy measure for several risk factors related to cumulative exercise load during the career of racehorses. Measurement of serum concentrations of pNF-H in TB racehorses does not support the hypothesis that subclinical neurologic injury or conditions are associated with catastrophic injury of TB racehorses.

A Method to Combine Neurofilament Light Measurements From Blood Serum and Plasma in Clinical and Population-Based Studies

Introduction

Neurofilament light (NfL) can be detected in blood of healthy individuals and at elevated levels in those with different neurological diseases. We investigated if the choice of biological matrix can affect results when using NfL as biomarker in epidemiological studies.

Method

We obtained paired serum and EDTA-plasma samples of 299 individuals aged 37–67 years (BiDirect study) and serum samples of 373 individuals aged 65–83 years (MEMO study). In BiDirect, Passing–Bablok analyses were performed to assess proportional and systematic differences between biological matrices. Associations between serum or EDTA-plasma NfL and renal function (serum creatinine, serum cystatin C, glomerular filtration rate, and kidney disease) were investigated using linear or logistic regression, respectively. All regression coefficients were estimated (1) per one ng/L increase and (2) per one standard deviation increase (standardization using z-scores). In MEMO, regression coefficients were estimated (1) per one ng/L increase of serum or calculated EDTA-plasma NfL and (2) per one standard deviation increase providing a comparison to the results from BiDirect.

Results

We found proportional and systematic differences between paired NfL measurements in BiDirect, i.e., serum NfL [ng/L] = −0.33 [ng/L] + 1.11 × EDTA-plasma NfL [ng/L]. Linear regression coefficients for the associations between NfL and renal function did not vary between the different NfL measurements. In MEMO, one standard deviation increase in serum NfL was associated with greater changes in the outcomes than in BiDirect.

Conclusion

Although there are differences between serum and EDTA-plasma NfL, results can be used interchangeably if standardized values are used.

Association Between EEG Patterns and Serum Neurofilament Light After Cardiac Arrest

Background and Objectives

EEG is widely used for prediction of neurologic outcome after cardiac arrest. To better understand the relationship between EEG and neuronal injury, we explored the association between EEG and neurofilament light (NfL) as a marker of neuroaxonal injury, evaluated whether highly malignant EEG patterns are reflected by high NfL levels, and explored the association of EEG backgrounds and EEG discharges with NfL.

Methods

We performed a post hoc analysis of the Target Temperature Management After Out-of-Hospital Cardiac Arrest trial. Routine EEGs were prospectively performed after the temperature intervention ≥36 hours postarrest. Patients who awoke or died prior to 36 hours postarrest were excluded. EEG experts blinded to clinical information classified EEG background, amount of discharges, and highly malignant EEG patterns according to the standardized American Clinical Neurophysiology Society terminology. Prospectively collected serum samples were analyzed for NfL after trial completion. The highest available concentration at 48 or 72 hours postarrest was used.

Results

A total of 262/939 patients with EEG and NfL data were included. Patients with highly malignant EEG patterns had 2.9 times higher NfL levels than patients with malignant patterns and NfL levels were 13 times higher in patients with malignant patterns than those with benign patterns (95% CI 1.4–6.1 and 6.5–26.2, respectively; effect size 0.47; p < 0.001). Both background and the amount of discharges were independently strongly associated with NfL levels (p < 0.001). The EEG background had a stronger association with NfL levels than EEG discharges (R² = 0.30 and R² = 0.10, respectively). NfL levels in patients with a continuous background were lower than for any other background (95% CI for discontinuous, burst-suppression, and suppression, respectively: 2.26–18.06, 3.91–41.71, and 5.74–41.74; effect size 0.30; p < 0.001 for all). NfL levels did not differ between suppression and burst suppression. Superimposed discharges were only associated with higher NfL levels if the EEG background was continuous.

Discussion

Benign, malignant, and highly malignant EEG patterns reflect the extent of brain injury as measured by NfL in serum. The extent of brain injury is more strongly related to the EEG background than superimposed discharges. Combining EEG and NfL may be useful to better identify patients misclassified by single methods.

Trial Registration Information

ClinicalTrials.gov NCT01020916.

Effects of Fish Oil on Biomarkers of Axonal Injury and Inflammation in American Football Players: A Placebo-Controlled Randomized Controlled Trial

There are limited studies on neuroprotection from repeated subconcussive head impacts (RSHI) following docosahexaenoic acid (DHA) + eicosapentaenoic acid (EPA) supplementation in contact sports athletes. We performed a randomized, placebo-controlled, double-blinded, parallel-group design trial to determine the impact of 26 weeks of DHA+EPA supplementation (n = 12) vs. placebo (high-oleic safflower oil) (n = 17) on serum concentrations of neurofilament light (NfL), a biomarker of axonal injury, and inflammatory cytokines (interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-a)) in National Collegiate Athletic Association Division I American football athletes. DHA+EPA supplementation increased (p < 0.01) plasma DHA and EPA concentrations throughout the treatment period. NfL concentrations increased from baseline to week 26 in both groups (treatment (<0.001); placebo (p < 0.05)), with starting players (vs. non-starters) showing significant higher circulating concentrations at week 26 (p < 0.01). Fish oil (DHA+EPA) supplementation did not mitigate the adverse effects of RSHI, as measured by NfL levels; however, participants with the highest plasma DHA+EPA concentrations tended to have lower NfL levels. DHA+EPA supplementation had no effects on inflammatory cytokine levels at any of the timepoints tested. These findings emphasize the need for effective strategies to protect American football participants from the effects of RSHI.

Evaluation of serum neurofilament light in the early management of mTBI patients

OBJECTIVES

Serum S100B allows a one-third reduction of computed tomography (CT) scans performed for mild traumatic brain injury (mTBI) patients. In this study, we evaluated the diagnostic performance of serum NF-L in the detection of intracranial lesions induced by mTBI.

METHODS

One hundred seventy-nine adult mTBI patients presenting to the emergency department of Clermont-Ferrand University Hospital with a Glasgow Coma Scale (GCS) score of 14-15 were included. S100B assays were performed for clinical routine while NF-L samples were stored at -80 °C until analysis. CT scans were performed for patients with S100B levels above the decision threshold of 0.10 μg/L. Later, NF-L and S100B levels were compared to CT scan findings to evaluate the biomarkers' performances.

RESULTS

The area under the ROC curve (AUC) evaluating the diagnostic ability in the prediction of intracranial lesions was 0.72 (95% CI; 0.58-0.87) for S100B and 0.58 (95% CI; 0.45-0.71) for NF-L, the specificities (at a threshold allowing a 100% sensitivity) were 35.7% for S100B, and 28% for NF-L (p=0.096). AUCs of NF-L and S100B for the identification of patients with neurological disorders were statistically different (p<0.001). The AUCs were 0.87 (95% CI; 0.82-0.93) for NF-L and 0.57 (95% CI; 0.48-0.66) for S100B. There was a poor correlation between NF-L and S100B, and NF-L levels were correlated to patients' age (Spearman coefficient of 0.79).

CONCLUSIONS

NF-L showed poor performances in the early management of mTBI patients. NF-L levels are strongly correlated to neurodegeneration, whether physiological, age-related, or pathological.

Blood biomarkers for Alzheimer's disease and related disorders

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the single commonest cause of dementia. Many other diseases can, however, cause dementia, and differential diagnosis can be challenging, especially in early disease stages. For most neurodegenerative dementias, accumulation of brain pathologies starts many years before clinical onset; the ability to detect these pathologies paves the way for targeted disease-modifying prevention trials. AD is associated with β-amyloid and tau pathologies, which can be quantified using cerebrospinal fluid and imaging biomarkers and, more recently, using highly sensitive blood tests. While for the most part, specific biomarkers of non-AD neurodegenerative dementias are lacking, non-specific biomarkers of neurodegeneration are available. This review summarizes recent advances in the neurodegenerative dementia blood biomarker research and discusses the next steps required for clinical implementation.

Prospectively Assessing Serum Neurofilament Light Chain Levels As A Biomarker Of Paclitaxel-Induced Peripheral Neurotoxicity In Breast Cancer Patients

Our aim was to assess the significance of measuring serum neurofilament light chain (sNfL) levels as biomarker of paclitaxel-induced peripheral neurotoxicity (PIPN). We longitudinally measured sNfL in breast cancer patients, scheduled to receive the 12-weekly paclitaxel-based regimen. Patients were clinically examined by means of the Total Neuropathy Score-clinical version (TNSc), while sNfL were quantified, using the highly-sensitive Simoa technique, before starting chemotherapy (Baseline), after 2 (week-2) and 3 (week-3) weekly courses, and at the end of chemotherapy (week-12). Among 59 included patients (mean age: 53.1±11.5 years), 33 (56%) developed grade 0-1 and 26 (44%) grade 2-3 PIPN at week-12. A significant longitudinal increase of sNfL levels from baseline to week-12 was determined, whereas patients wth TNSc grade 2-3 PIPN had significantly increased sNfL levels at week-12, compared to those with grade 0-1. ROC analysis defined a value of NfL of >85 pg/mL at week-3 as the best discriminative determination to predict the development of grade 2-3 PIPN at week-12 (sensitivity 46.2%, specificity 84.8%). The logistic binary regression analysis revealed that age >50 years and the cutoff of >85 pg/mL of sNfL levels at week-3 independently predicted the development of grade 2-3 PIPN at week-12 with a sensitivity of 46%, a specificity of 91%, and a positive and negative predictive values of 75% and 67%, respectively. sNfL levels seem to be a valuable biomarker of neuro-axonal injury in PIPN. Early increase of this biomarker after a 3 weekly chemotherapy course can be a predictive marker of final PIPN severity. This article is protected by copyright. All rights reserved.

Pre-analytical stability of serum biomarkers for neurological disease: neurofilament-light, glial fibrillary acidic protein and contactin-1

OBJECTIVES

Neurofilament-light (NfL), glial fibrillary acidic protein (GFAP) and contactin-1 (CNTN1) are blood-based biomarkers that could contribute to monitoring and prediction of disease and treatment outcomes in neurological diseases. Pre-analytical sample handling might affect results, which could be disease-dependent. We tested common handling variations in serum of volunteers as well as in a defined group of patients with multiple sclerosis (pwMS).

METHODS

Sample sets from 5 pwMS and 5 volunteers at the outpatient clinic were collected per experiment. We investigated the effect of the following variables: collection tube type, delayed centrifugation, centrifugation temperature, delayed storage after centrifugation and freeze-thawing. NfL and GFAP were measured by Simoa and CNTN1 by Luminex. A median recovery of 90-110% was considered stable.

RESULTS

For most pre-analytical variables, serum NfL and CNTN1 levels remained unaffected. In the total group, NfL levels increased (121%) after 6 h of delay at 2-8 °C until centrifugation, while no significant changes were observed after 24 h delay at room temperature (RT). In pwMS specifically, CNTN1 levels increased from additional freeze-thaw cycles number 2 to 4 (111%-141%), whereas volunteer levels remained stable. GFAP showed good stability for all pre-analytical variables.

CONCLUSIONS

Overall, the serum biomarkers tested were relatively unaffected by variations in sample handling. For serum NfL, we recommend storage at RT before centrifugation at 2-8 °C up to 6 h or at RT up to 24 h. For serum CNTN1, we advise a maximum of two freeze-thaw cycles. Our results confirm and expand on recently launched consensus standardized operating procedures.

Type of serum collection tube does not impact neurofilament light chain levels

Blood neurofilament light chain (NfL) has been reported to be a promising biomarker of neurological disease. NfL is predominantly measured in serum (sNfL), but there is a lack of reports regarding the effects of collection tubes on sNfL levels. We assessed sNfL levels using a novel immunoassay in 18 participants using 3 different types of serum collection tubes (no additive, with silica clot activator, and serum separator tubes). Variation observed in sNfL levels between samples from different collection tubes was similar to that observed in duplicate runs from the same tube. These findings support a lack of effect of type of serum collection tube on sNfL levels.

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.

Neurofilament proteins as potential biomarker in chemotherapy-induced polyneuropathy

BACKGROUND

Paclitaxel chemotherapy frequently induces dose-limiting sensory axonal polyneuropathy. As sensory symptoms are challenging to assess objectively in clinical routine, an easily accessible biomarker for chemotherapy-induced polyneuropathy (CIPN) holds the potential to improve early diagnosis. Here, we describe neurofilament light chain (NFL), a marker for neuroaxonal damage, as translational surrogate marker for CIPN.

METHODS

NFL concentrations were measured in an in vitro model of CIPN, exposing induced pluripotent stem cell-derived sensory neurons (iPSC-DSN) to paclitaxel. Breast and ovarian cancer patients undergoing paclitaxel chemotherapy, breast cancer control patients without chemotherapy and healthy controls were recruited in a cohort study and examined before chemotherapy (V1) and after 28 weeks (V2, after chemotherapy). CIPN was assessed by the validated Total Neuropathy Score reduced, which combines patient-reported symptoms with data from clinical examinations. Serum NFL (NFLs) concentrations were measured at both visits with single molecule array technology (SIMOA).

RESULTS

NFL is released from iPSC-DSN upon paclitaxel incubation in a dose- and time-dependent manner and inversely correlates with iPSC-DSN viability. NFLs strongly increased in paclitaxel-treated patients with CIPN, but not in chemotherapy patients without CIPN or controls, resulting in an 86 % sensitivity and 87 % specificity. A NFLs increase of +36 pg/ml from baseline was associated with a predicted CIPN probability of >0.5.

CONCLUSION

NFLs correlates with CIPN development and severity, which may guide neurotoxic chemotherapy in the future.

TRIAL REGISTRATION

NCT02753036FUNDING. DFG (EXC 257 NeuroCure), BMBF (01 EO 0801), AnimalFreeResearch Organization, EU Horizon 2020 Innovative Medicines Initiative 2 Joint Undertaking (TransBioLine, 821283).

The wearing-off phenomenon of ocrelizumab in patients with multiple sclerosis

BACKGROUND

Patients with multiple sclerosis (MS) who are treated with monoclonal antibodies frequently report an increase of MS-related symptoms prior to the next dose known as the wearing-off phenomenon. The objective of this study was to assess the prevalence and predicting factors of the wearing-off phenomenon in patients with MS using ocrelizumab.

METHODS

This was a prospective cohort study in patients with MS receiving ocrelizumab ≥1 year. Most participants received B-cell guided personalized extended interval dosing to limit ocrelizumab exposure and hospital visits during the COVID-19 pandemic (cut-off ≥ 10 cells/µL). Participants completed questionnaires during ocrelizumab infusion and 2 weeks thereafter. Demographics, clinical and radiological characteristics, CD19 B-cell counts, and serum neurofilament light (sNfL) levels were collected. Data were analyzed using logistic regression analyses.

RESULTS

Seventy-one (61%) out of 117 participants reported the wearing-off phenomenon during ocrelizumab treatment. The most frequently reported symptoms were fatigue, cognitive disability and sensory symptoms. Wearing-off symptoms started < 1 week (11%), 1-4 weeks (49%) or more than 4 weeks (37%) before ocrelizumab infusion. Fifty participants (43%) reported a current wearing-off phenomenon at the first questionnaire. Higher body mass index (threshold BMI ≥ 25) increased the odds of reporting a current wearing-off phenomenon (OR 2.70, 95% CI 1.26 to 5.80, p = .011). Infusion interval, EDSS score, MRI disease activity, clinical relapses, CD19 B-cell counts, and sNfL levels were no predictors. Disappearance of the wearing-off phenomenon occurred in the first week after ocrelizumab infusion in most participants. Participants with a current wearing-off phenomenon significantly improved in self-reported physical and psychological functioning after ocrelizumab infusion. Reporting the wearing-off phenomenon did not influence treatment satisfaction. Forty of 109 participants (37%) reported post-infusion symptoms, such as fatigue, flu-like symptoms or walking difficulties. These post-infusion symptoms started directly or in the first week after ocrelizumab infusion and disappeared within 2 weeks.

CONCLUSIONS

The wearing-off phenomenon is reported by more than half of patients with MS using ocrelizumab. Only BMI was identified as a predicting factor. The wearing-off phenomenon was not elicited by extending infusion intervals or higher B-cell counts. The wearing-off phenomenon of ocrelizumab therefore does not seem to reflect suboptimal control of MS disease activity.

Diffusely abnormal white matter in clinically isolated syndrome is associated with parenchymal loss and elevated neurofilament levels

We characterized the frequency of diffusely abnormal white matter (DAWM) across a broad spectrum of multiple sclerosis (MS) participants. 35% of clinically isolated syndrome (CIS), 57% of relapsing remitting and 64% of secondary progressive MS participants demonstrated DAWM. CIS with DAWM had decreased cortical thickness, higher lesion load and a higher concentration of serum neurofilament light chain compared to CIS without DAWM. DAWM may be useful in identifying CIS patients with greater injury to their brains. Larger and longitudinal studies are warranted.

Serum neurofilament light chain levels as biomarker of paclitaxel-induced cognitive impairment in patients with breast cancer: a prospective study

OBJECTIVE

To prospectively assess the utility of serum neurofilament light chain (sNfL) levels in identifying the risk to develop chemotherapy-induced cognitive impairment (CICI) in cancer patients. We also examined if sNfL can be identified as an early biomarker of CICI development.

METHODS

We longitudinally measured sNfL levels in 20 female patients with breast cancer, scheduled to receive the 12 weekly paclitaxel-based regimen. An equal number of age-matched female heathy subjects was incuded as control group. CICI was graded by means of the Montreal Cognitive Assessment scale (MOCA); peripheral neurotoxicity (PN) was graded using the neurosensory Common Criteria for Adverse Events (CTCAE)v5.0, while sNfL levels were quantified using a high-sensitive technique (Quanterix, Simoa) before the administration of chemotherapy (T0), after 3 courses (T1), and at the end of chemotherapy (T2).

RESULTS

Pre-treatment sNfL levels were comparable in patients and controls (p = 0.103). At T2, 5/20 patients (mean age 61.4 ± 5.0 years) developed CICI. These 5 patients also had clinically-significant PN. Patients with and without CICI had comparable sNfL values at T2 (p = 0.1). In addition, at T2, sNfL levels did not correlate significantly with MOCA score in CICI patients (p = 0.604). The difference of sNfL levels between T1 and T0 failed to predict independently the occurrence of CICI at T2.

CONCLUSION

Our findings do not support the utility of measuring sNfL levels as a biomarker of CICI. Grade 2-3 PN most strongly confounded our outcomes. Considering the small sample size, which might have prevented the results from being extrapolated, further testing in larger studies is warranted.

Neurofilament Proteins as Biomarkers to Monitor Neurological Diseases and the Efficacy of Therapies

Biomarkers of neurodegeneration and neuronal injury have the potential to improve diagnostic accuracy, disease monitoring, prognosis, and measure treatment efficacy. Neurofilament proteins (NfPs) are well suited as biomarkers in these contexts because they are major neuron-specific components that maintain structural integrity and are sensitive to neurodegeneration and neuronal injury across a wide range of neurologic diseases. Low levels of NfPs are constantly released from neurons into the extracellular space and ultimately reach the cerebrospinal fluid (CSF) and blood under physiological conditions throughout normal brain development, maturation, and aging. NfP levels in CSF and blood rise above normal in response to neuronal injury and neurodegeneration independently of cause. NfPs in CSF measured by lumbar puncture are about 40-fold more concentrated than in blood in healthy individuals. New ultra-sensitive methods now allow minimally invasive measurement of these low levels of NfPs in serum or plasma to track disease onset and progression in neurological disorders or nervous system injury and assess responses to therapeutic interventions. Any of the five Nf subunits - neurofilament light chain (NfL), neurofilament medium chain (NfM), neurofilament heavy chain (NfH), alpha-internexin (INA) and peripherin (PRPH) may be altered in a given neuropathological condition. In familial and sporadic Alzheimer's disease (AD), plasma NfL levels may rise as early as 22 years before clinical onset in familial AD and 10 years before sporadic AD. The major determinants of elevated levels of NfPs and degradation fragments in CSF and blood are the magnitude of damaged or degenerating axons of fiber tracks, the affected axon caliber sizes and the rate of release of NfP and fragments at different stages of a given neurological disease or condition directly or indirectly affecting central nervous system (CNS) and/or peripheral nervous system (PNS). NfPs are rapidly emerging as transformative blood biomarkers in neurology providing novel insights into a wide range of neurological diseases and advancing clinical trials. Here we summarize the current understanding of intracellular NfP physiology, pathophysiology and extracellular kinetics of NfPs in biofluids and review the value and limitations of NfPs and degradation fragments as biomarkers of neurodegeneration and neuronal injury.

Serum markers of brain injury can predict good neurological outcome after out-of-hospital cardiac arrest

PURPOSE

The majority of unconscious patients after cardiac arrest (CA) do not fulfill guideline criteria for a likely poor outcome, their prognosis is considered "indeterminate". We compared brain injury markers in blood for prediction of good outcome and for identifying false positive predictions of poor outcome as recommended by guidelines.

METHODS

Retrospective analysis of prospectively collected serum samples at 24, 48 and 72 h post arrest within the Target Temperature Management after out-of-hospital cardiac arrest (TTM)-trial. Clinically available markers neuron-specific enolase (NSE) and S100B, and novel markers neurofilament light chain (NFL), total tau, ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) and glial fibrillary acidic protein (GFAP) were analysed. Normal levels with a priori cutoffs specified by reference laboratories or defined from literature were used to predict good outcome (no to moderate disability, Cerebral Performance Category scale 1-2) at 6 months.

RESULTS

Seven hundred and seventeen patients were included. Normal NFL, tau and GFAP had the highest sensitivities (97.2-98% of poor outcome patients had abnormal serum levels) and NPV (normal levels predicted good outcome in 87-95% of patients). Normal S100B and NSE predicted good outcome with NPV 76-82.2%. Normal NSE correctly identified 67/190 (35.3%) patients with good outcome among those classified as "indeterminate outcome" by guidelines. Five patients with single pathological prognostic findings despite normal biomarkers had good outcome.

CONCLUSION

Low levels of brain injury markers in blood are associated with good neurological outcome after CA. Incorporating biomarkers into neuroprognostication may help prevent premature withdrawal of life-sustaining therapy.

Serum neurofilament light chain as a surrogate of cognitive decline in sporadic and familial frontotemporal dementia

BACKGROUND AND PURPOSE

Neurofilament light chain (NfL) has recently been proposed as a promising biomarker in frontotemporal dementia (FTD). We investigated the correlation of both cerebrospinal fluid (CSF) and serum NfL with detailed neuropsychological data and cognitive decline in a cohort of sporadic and familial FTD.

METHODS

CSF and serum NfL, as well as conventional CSF Alzheimer's disease (AD) biomarkers (Aβ42, t-Tau, p-Tau181), were determined in 63 FTD patients (30 sporadic-FTD, 20 with progranulin (GRN) mutations [FTD-GRN], 13 with chromosome 9 open reading frame 72 [C9orf72] expansions [C9orf72-FTD]), 37 AD patients, and 31 neurologic controls. Serum NfL was also quantified in 37 healthy individuals. Correlations between baseline CSF and serum NfL levels, standardized neuropsychological tests, and the rate of cognitive decline in FTD patients were assessed.

RESULTS

CSF and serum NfL presented with significantly higher levels in FTD than in AD patients and both control groups. Within FTD subtypes, genetic cases, and particularly FTD-GRN, had higher CSF and serum NfL levels. Significant correlations between NfL levels and overall cognitive function, abstract reasoning (CSF and serum), executive functions, memory, and language (serum) were found. A relationship between increased baseline CSF and serum NfL and a decay in cognitive performance over time was also observed.

CONCLUSIONS

Our findings highlight the potential of serum NfL as a useful surrogate end point of disease severity in upcoming targeted treatments.

Neurological symptoms and axonal damage in COVID-19 survivors: are there sequelae?

The persistence of neurological symptoms after SARS-CoV-2 infection, as well as the presence of late axonal damage, is still unknown. We performed extensive systemic and neurological follow-up evaluations in 107 out of 193 consecutive patients admitted to the COVID-19 medical unit, University Hospital of Verona, Italy between March and June 2020. We analysed serum neurofilament light chain (NfL) levels in all cases including a subgroup (n = 29) of patients with available onset samples. Comparisons between clinical and biomarker data were then performed. Neurological symptoms were still present in a significant number (n = 49) of patients over the follow-up. The most common reported symptoms were hyposmia (n = 11), fatigue (n = 28), myalgia (n = 14), and impaired memory (n = 11) and were more common in cases with severe acute COVID-19. Follow-up serum NfL values (15.2 pg/mL, range 2.4–62.4) were within normal range in all except 5 patients and did not differentiate patients with vs without persistent neurological symptoms. In patients with available onset and follow-up samples, a significant (p < 0.001) decrease of NfL levels was observed and was more evident in patients with a severe acute disease. Despite the common persistence of neurological symptoms, COVID-19 survivors do not show active axonal damage, which seems a peculiar feature of acute SARS-CoV-2 infection.

Prediction of Neurological Recovery After Cardiac Arrest Using Neurofilament Light Chain is Improved by a Proteomics-Based Multimarker Panel

BACKGROUND

Continuous advances in resuscitation care have increased survival, but the rate of favorable neurological outcome remains low. We have shown the usefulness of proteomics in identifying novel biomarkers to predict neurological outcome. Neurofilament light chain (NfL), a marker of axonal damage, has since emerged as a promising single marker. The aim of this study was to assess the predictive value of NfL in comparison with and in addition to our established model.

METHODS

NfL was measured in plasma samples drawn at 48 h after cardiac arrest using single-molecule assays. Neurological function was recorded on the cerebral performance category (CPC) scale at discharge from the intensive care unit and after 6 months. The ability to predict a dichotomized outcome (CPC 1-2 vs. 3-5) was assessed with receiver operating characteristic (ROC) curves.

RESULTS

Seventy patients were included in this analysis, of whom 21 (30%) showed a favorable outcome (CPC 1-2), compared with 49 (70%) with an unfavorable outcome (CPC 3-5) at discharge. NfL increased from CPC 1 to 5 (16.5 pg/ml to 641 pg/ml, p < 0.001). The addition of NfL to the existing model improved it significantly (Wald test, p < 0.001), and the combination of NfL with a multimarker model showed high areas under the ROC curve (89.7% [95% confidence interval 81.7-97.7] at discharge and 93.7% [88.2-99.2] at 6 months) that were significantly greater than each model alone.

CONCLUSIONS

The combination of NfL with other plasma and clinical markers is superior to that of either model alone and achieves high areas under the ROC curve in this relatively small sample.

Chronic fatigue syndrome: an emerging sequela in COVID-19 survivors?

SARS-CoV-2 survivors may report persistent symptoms that resemble myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We explored (a) ME/CFS-like symptom prevalence and (b) whether axonal, inflammatory, and/or lung changes may contribute to ME/CFS-like symptoms in SARS-CoV-2 survivors through clinical, neuropsychiatric, neuropsychological, lung function assessment, and serum neurofilament light chain, an axonal damage biomarker. ME/CFS-like features were found in 27% of our sample. ME/CFS-like group showed worse sleep quality, fatigue, pain, depressive symptoms, subjective cognitive complaints, Borg baseline dyspnea of the 6-min walking test vs. those without ME/CFS-like symptoms. These preliminary findings raise concern on a possible future ME/CFS-like pandemic in SARS-CoV-2 survivors.

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.

Serum neurofilament light chain levels in healthy individuals: A proposal of cut-off values for use in multiple sclerosis clinical practice

BACKGROUND

Serum Neurofilament Light (sNFL) is the most promising marker for patient's monitoring in Multiple Sclerosis (MS). However, operating reference values for use in clinical practice are still lacking. Here, we defined sNFL reference cut-off values in a cohort of healthy controls (HC) and assessed their performance in Multiple Sclerosis (MS) patients, as well as the intra-individual sNFL variability.

METHODS

We measured sNFL by single molecule array (Simoa) assay in 79 HC assessing their correlation with age. Changes of sNFL levels were evaluated during a short-term follow-up (median 67 days between consecutive samples) in a subgroup of 27 participants. sNFL were tested in 23 untreated MS patients, at both diagnostic time and start of therapy (median 80 days after), considering disease activity.

RESULTS

Findings confirmed a correlation between sNFL levels and age in HC, thus cut-off values specific for age decades were calculated. sNFL did not vary significantly with time during short-term follow-up (median CV 13%). sNFL levels in MS patients were higher and demonstrated a higher variability between diagnostic time and treatment start (median CV 39%). According to cut-off values, "pathologic" sNFL levels were found in 57% of MS patients at diagnostic time, and in 30% of samples at treatment start. In particular, "pathologic" sNFL levels were found in 80% of samples (16/20) obtained during a phase of disease activity, while a total of 85% of samples (22/26) associated with inactive disease showed sNFL in the normal range.

CONCLUSION

This study demonstrates an overall intra-individual stability of sNFL values in the short-term in HC and suggests age-dependent reference cut-off values that could be beneficial for sNFL implementation in clinical practice.

Seven day pre-analytical stability of serum and plasma neurofilament light chain

Neurofilament light chain (NfL) has emerged as a biomarker of neuroaxonal damage in several neurologic conditions. With increasing availability of fourth-generation immunoassays detecting NfL in blood, aspects of pre-analytical stability of this biomarker remain unanswered. This study investigated NfL concentrations in serum and plasma samples of 32 patients with neurological diagnoses using state of the art Simoa technology. We tested the effect of delayed freezing of up to 7 days and statistically determined stability and validity of measured concentrations. We found concentrations of NfL in serum and plasma to remain stable at room temperature when processing of samples is delayed up to 7 days (serum: mean absolute difference 0.9 pg/mL, intraindividual variation 1.2%; plasma: mean absolute difference 0.5 pg/mL, intraindividual variation 1.3%). Consistency of these results was nearly perfect for serum and excellent for plasma (intraclass correlation coefficients 0.99 and 0.94, respectively). In conclusion, the soluble serum and plasma NfL concentration remains stable when unprocessed blood samples are stored up to 7 days at room temperature. This information is essential for ensuring reliable study protocols, for example, when shipment of fresh samples is needed.

Serum Neurofilament Light Chain Measurement in MS: Hurdles to Clinical Translation

Measurement of serum neurofilament light chain concentration (sNfL) promises to become a convenient, cost effective and meaningful adjunct for multiple sclerosis (MS) prognostication as well as monitoring disease activity in response to treatment. Despite the remarkable progress and an ever-increasing literature supporting the potential role of sNfL in MS over the last 5 years, a number of hurdles remain before this test can be integrated into routine clinical practice. In this review we highlight these hurdles, broadly classified by concerns relating to clinical validity and analytical validity. After setting out an aspirational roadmap as to how many of these issues can be overcome, we conclude by sharing our vision of the current and future role of sNfL assays in MS clinical practice.

Biological variation of serum neurofilament light chain

OBJECTIVES

The neurofilament light chain (NfL) has emerged as a versatile biomarker for CNS-diseases and is approaching clinical use. The observed changes in NfL levels are frequently of limited magnitude and in order to make clinical decisions based on NfL measurements, it is essential that biological variation is not confused with clinically relevant changes. The present study was designed to evaluate the biological variation of serum NfL.

METHODS

Apparently healthy individuals (n=33) were submitted to blood draws for three days in a row. On the second day, blood draws were performed every third hour for 12 h. NfL was quantified in serum using the Simoa™ HD-1 platform. The within-subject variation (CV_I) and between-subject variation (CV_G) were calculated using linear mixed-effects models.

RESULTS

The overall median value of NfL was 6.3 pg/mL (range 2.1-19.1). The CV_I was 3.1% and the CV_G was 35.6%. An increase in two serial measurements had to exceed 24.3% to be classified as significant at the 95% confidence level. Serum NfL levels remained stable during the day (p=0.40), whereas a minute variation (6.0-6.6 pg/mL) was observed from day-to-day (p=0.02).

CONCLUSIONS

Serum NfL is subject to tight homeostatic regulation with none or neglectable semidiurnal and day-to-day variation, but considerable between-subject variation exists. This emphasizes serum NfL as a well-suited biomarker for disease monitoring, but warrants caution when interpreting NfL levels in relation to reference intervals in a diagnosis setting. Furthermore, NfL's tight regulation requires that the analytical variation is kept at a minimum.

Blood neurofilament light in remote settings: Alternative protocols to support sample collection in challenging pre-analytical conditions

INTRODUCTION

This study investigated alternative pre-analytical handling of blood for neurofilament light (NfL) analysis where resources are limited.

METHOD

Plasma NfL was measured with single molecule array after alternative blood processing procedures: dried plasma spots (DPS), dried blood spots (DBS), and delayed 48-hour centrifugation. These were compared to standardized plasma processing (reference standard [RS]). In a discovery cohort (n = 10) and a confirmatory cohort (n = 21), whole blood was obtained from individuals with unknown clinical etiology. In the confirmatory cohort, delayed centrifugation protocol was paired with either 37°C incubation or sample shaking to test the effect of these parameters.

RESULTS

Delayed centrifugation (R2 = 0.991) and DPS (discovery cohort, R2 = 0.954; confirmatory cohort, DPS: R2 = 0.961) methods were strongly associated with the RS. Delayed centrifugation with higher temperatures (R2 = 0.995) and shaking (R2 = 0.975) did not affect this association. DPS (P < 0.001) returned concentrations considerably lower than the RS.

DISCUSSION

DPS or delayed centrifugation are viable pre-analytical procedures for the accurate quantification of plasma NfL.

Plasma neurofilament light chain as a potential biomarker in Charcot-Marie-Tooth disease

BACKGROUND AND PURPOSE

Charcot-Marie-Tooth (CMT) disease is a chronic, slowly progressing disorder. The lack of specific disease progression biomarkers limits the execution of clinical trials. However, neurofilament light chain (NfL) has been suggested as a potential biomarker for peripheral nervous system disorders.

METHODS

Ninety-six CMT disease patients and 60 healthy controls were enrolled in the study. Disease severity assessment included clinical evaluation with CMT Neuropathy Score version 2 (CMTNSv2). Blood plasma NfL concentrations were measured using the single-molecule array NfL assay.

RESULTS

The NfL concentration was significantly higher in the CMT disease patient group than in the controls (p < 0.001). Of the CMT disease patients, those with type CMTX1 had a higher NfL level than those in the two other analysed subgroups (CMT1A and other CMT disease types) (p = 0.0498). The NfL concentration had a significant but weak correlation with the CMTNSv2 (r_s  = 0.25, p = 0.012). In one CMT disease patient with an extremely elevated NfL level, overlap with chronic inflammatory demyelinating polyneuropathy was suspected. Receiver operating characteristic analysis showed that an NfL concentration of 8.9 pg/ml could be used to discriminate CMT disease patients from controls, with an area under the curve of 0.881.

CONCLUSIONS

Our study confirmed that the plasma NfL concentration is significantly higher in CMT disease patients than in controls. Plasma NfL concentration was found to significantly, albeit weakly, reflect the clinical severity of CMT disease. In the future, NfL may be used, either individually or collaboratively, as a biomarker in the clinical context of suspected CMT disease; however, several issues need to be addressed first.

Renal function is associated with blood neurofilament light chain level in older adults

Neurofilament light chain (NfL) is a novel biomarker of neurodegenerative diseases. It is detectable in the peripheral blood, allowing low-invasive assessment of early signs of neurodegeneration. The level of NfL gradually increases with age; however, what other factors affect it remains unclear. The present study examined the association between blood NfL level and renal function among healthy participants undergoing a health check (n = 43, serum NfL) and patients with diabetes mellitus (n = 188, plasma NfL). All participants were 60 years of age or older; none were diagnosed with dementia. In each group, levels of blood NfL and serum creatinine significantly correlated (coefficient r = 0.50, 0.56). These associations remained statistically significant even after adjustment for age, sex, and body mass index. These findings indicate that blood NfL level might be partially affected by renal function. We recommend measuring renal function for a more precise evaluation of neuroaxonal damage, in particular, among older adults.

Serum neurofilament light chain withstands delayed freezing and repeated thawing

Serum neurofilament light chain (sNfL) and its ability to expose axonal damage in neurologic disorders have solicited a considerable amount of attention in blood biomarker research. Hence, with the proliferation of high-throughput assay technology, there is an imminent need to study the pre-analytical stability of this biomarker. We recruited 20 patients with common neurological diagnoses and 10 controls (i.e. patients without structural neurological disease). We investigated whether a variation in pre-analytical variables (delayed freezing up to 24 h and repeated thawing/freezing for up to three cycles) affects the measured sNfL concentrations using state of the art Simoa technology. Advanced statistical methods were applied to expose any relevant changes in sNfL concentration due to different storing and processing conditions. We found that sNfL concentrations remained stable when samples were frozen within 24 h (mean absolute difference 0.2 pg/ml; intraindividual variation below 0.1%). Repeated thawing and re-freezing up to three times did not change measured sNfL concentration significantly, either (mean absolute difference 0.7 pg/ml; intraindividual variation below 0.2%). We conclude that the soluble sNfL concentration is unaffected at 4–8 °C when samples are frozen within 24 h and single aliquots can be used up to three times. These observations should be considered for planning future studies.

Blood neurofilament light: a critical review of its application to neurologic disease

Neuronal injury is a universal event that occurs in disease processes that affect both the central and peripheral nervous systems. A blood biomarker linked to neuronal injury would provide a critical measure to understand and treat neurologic diseases. Neurofilament light chain (NfL), a cytoskeletal protein expressed only in neurons, has emerged as such a biomarker. With the ability to quantify neuronal damage in blood, NfL is being applied to a wide range of neurologic conditions to investigate and monitor disease including assessment of treatment efficacy. Blood NfL is not specific for one disease and its release can also be induced by physiological processes. Longitudinal studies in multiple sclerosis, traumatic brain injury, and stroke show accumulation of NfL over days followed by elevated levels over months. Therefore, it may be hard to determine with a single measurement when the peak of NfL is reached and when the levels are normalized. Nonetheless, measurement of blood NfL provides a new blood biomarker for neurologic diseases overcoming the invasiveness of CSF sampling that restricted NfL clinical application. In this review, we examine the use of blood NfL as a biologic test for neurologic disease.

Association of Serum Neurofilament Light Levels With Long-term Brain Atrophy in Patients With a First Multiple Sclerosis Episode

IMPORTANCE

Data are needed on the potential long-term prognostic association of serum neurofilament light in multiple sclerosis (MS).

OBJECTIVE

To evaluate serum neurofilament light as a biomarker associated with long-term disease outcomes in clinically isolated syndrome.

DESIGN, SETTING, AND PARTICIPANTS

This post hoc cohort study used data from the Controlled High-Risk Avonex Multiple Sclerosis Prevention Study, a 36-month, multicenter, placebo-controlled interferon β-1a randomized clinical trial conducted from April 1996 to March 2000, and its long-term (5- and 10-year) extension study from February 2001 to March 2009. Participants included individuals with a symptomatic initial demyelinating event and brain magnetic resonance imaging (MRI) lesions suggestive of MS. Data were analyzed from April 2017 through 2019.

EXPOSURE

The variable of interest was naturally occurring serum neurofilament light concentration.

MAIN OUTCOMES AND MEASURES

Gadolinium-enhancing (Gd+) lesion number, T2 lesion volume, and brain parenchymal fraction, a measure of brain atrophy were measured at baseline and 5 and 10 years. Multivariate regression models evaluated whether age, sex, and baseline covariates, including serum neurofilament light, brain parenchymal fraction, Expanded Disability Status Scale, Gd+ lesion count, and T2 lesion volume, were associated with brain parenchymal fraction changes over 5 and 10 years.

RESULTS

Among 308 included participants (mean [SD] age, 33.2 [7.6] years; 234 [76.0%] women), baseline serum neurofilament light concentrations were associated with Gd+ lesions (Spearman r = 0.41; P < .001) and T2 lesion volume (Spearman r = 0.42; P < .001). Among covariates for brain parenchymal fraction change, serum neurofilament light concentration had the greatest correlation with change in brain parenchymal fraction at 5 years (Spearman r = -0.38; P < .001) and was the only variable associated with brain parenchymal fraction at 10 years (Spearman r = -0.45; P < .001). Participants in the highest vs lowest baseline serum neurofilament light tertiles showed brain parenchymal fraction reduction at 5 years (-1.83% [95% CI, -1.49% to -2.18%] vs -0.95% [95% CI, -0.78% to -1.12%]; P < .001) and 10 years (-3.54% [95% CI, -2.90% to -4.17%] vs -1.90% [95% CI, -1.43% to -2.37%]; P < .001). At 5 years, 6 of 45 participants (13.3%) in the highest neurofilament tertile and 2 of 52 participants (3.8%) in the lowest neurofilament tertile achieved an Expanded Disability Status Scale score of 3.5 or greater.

CONCLUSIONS AND RELEVANCE

This cohort study found that higher baseline serum neurofilament light levels were associated with increased brain atrophy over 5 and 10 years. These findings suggest that serum neurofilament light could be a biomarker associated with disease severity stratification in early MS and may help to guide intervention.

Neurofilament light as an outcome predictor after cardiac arrest: a post hoc analysis of the COMACARE trial

Purpose

Neurofilament light (NfL) is a biomarker reflecting neurodegeneration and acute neuronal injury, and an increase is found following hypoxic brain damage. We assessed the ability of plasma NfL to predict outcome in comatose patients after out-of-hospital cardiac arrest (OHCA). We also compared plasma NfL concentrations between patients treated with two different targets of arterial carbon dioxide tension (PaCO₂), arterial oxygen tension (PaO₂), and mean arterial pressure (MAP).

Methods

We measured NfL concentrations in plasma obtained at intensive care unit admission and at 24, 48, and 72 h after OHCA. We assessed neurological outcome at 6 months and defined a good outcome as Cerebral Performance Category (CPC) 1–2 and poor outcome as CPC 3–5.

Results

Six-month outcome was good in 73/112 (65%) patients. Forty-eight hours after OHCA, the median NfL concentration was 19 (interquartile range [IQR] 11–31) pg/ml in patients with good outcome and 2343 (587–5829) pg/ml in those with poor outcome, p < 0.001. NfL predicted poor outcome with an area under the receiver operating characteristic curve (AUROC) of 0.98 (95% confidence interval [CI] 0.97–1.00) at 24 h, 0.98 (0.97–1.00) at 48 h, and 0.98 (0.95–1.00) at 72 h. NfL concentrations were lower in the higher MAP (80–100 mmHg) group than in the lower MAP (65–75 mmHg) group at 48 h (median, 23 vs. 43 pg/ml, p = 0.04). PaCO₂ and PaO₂ targets did not associate with NfL levels.

Conclusions

NfL demonstrated excellent prognostic accuracy after OHCA. Higher MAP was associated with lower NfL concentrations.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06218-9) contains supplementary material, which is available to authorized users.

Blood and cerebrospinal fluid neurofilament light differentially detect neurodegeneration in early Alzheimer's disease

Cerebrospinal fluid (CSF) neurofilament light (NfL) concentration has reproducibly been shown to reflect neurodegeneration in brain disorders, including Alzheimer's disease (AD). NfL concentration in blood correlates with the corresponding CSF levels, but few studies have directly compared the reliability of these 2 markers in sporadic AD. Herein, we measured plasma and CSF concentrations of NfL in 478 cognitively unimpaired (CU) subjects, 227 patients with mild cognitive impairment, and 113 patients with AD dementia. We found that the concentration of NfL in CSF, but not in plasma, was increased in response to Aβ pathology in CU subjects. Both CSF and plasma NfL concentrations were increased in patients with mild cognitive impairment and AD dementia. Furthermore, only NfL in CSF was associated with reduced white matter microstructure in CU subjects. Finally, in a transgenic mouse model of AD, CSF NfL increased before serum NfL in response to the development of Aβ pathology. In conclusion, NfL in CSF may be a more reliable biomarker of neurodegeneration than NfL in blood in preclinical sporadic AD.