• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • WTSSNH2Y - SSSNFL_H 2 year weights
  • SSSNFL - Serum neurofilament light chain (pg/ml)
  • SSNFLH - Serum neurofilament above detect limit
  • SSNFLL - Serum neurofilament below detect limit

National Health and Nutrition Examination Survey

2013-2014 Data Documentation, Codebook, and Frequencies

Serum Neurofilament Light Chain - Serum (SSSNFL_H)

Data File: SSSNFL_H.xpt

First Published: June 2022

Last Revised: NA

Component Description

Neurofilaments are neuron-specific type IV intermediate filament heteropolymers composed of light, medium, and heavy chains (Petzold, 2005). Neurofilaments are the dominant proteins of the neural cytoskeleton and are released into the extracellular space following neuro-axonal damage, and have thus been proposed as putative biomarkers of neuro-axonal injury in multiple neurological diseases (Petzold, 2005; Lépinoux-Chambaud and Eyer, 2013; Bacioglu et al., 2016). Neurofilament light chain (NfL) especially, has been shown to be a promising biomarker because of its high solubility, and increased NfL levels have been found in the blood and CSF in several neurological disorders with underlying neuro-axonal degeneration, including multiple sclerosis (MS), Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, motor neuron disease, stroke, inherited peripheral neuropathies, and traumatic brain injury (Gunnarsson et al., 2011; Disanto et al., 2016; Weydt et al., 2016; Byrne et al., 2017; De Marchis et al., 2018; Olsson et al., 2019). Elevated concentrations of NfL have also been associated with disease severity in these patient populations, including in MS and other neurologic conditions (Disanto et al., 2017; Preische et al., 2019). Importantly, serum neurofilament light chain (sNfL) has been shown to increase with age in healthy control cohorts; however, age-specific reference ranges have not been well-defined (Disanto et al., 2017). Taken together, higher sNfL values are observed in those with many neurological disorders; however, sNfL levels among those without neurological disorders tend to increase with age.This data will characterize sNfL levels across the age distribution in a representative sample of non-institutionalized US adults.

Eligible Sample

Participants aged 20-75 years in a half-sample from NHANES 2013-2014, who consented to storing their samples for future research and had stored surplus or pristine serum samples, were eligible.

Description of Laboratory Methodology

Siemens Healthineers has developed a highly sensitive NfL immunoassay that utilizes acridinium ester (AE) chemiluminescence and paramagnetic particles and may be run on an existing, high-throughput, automated platform (Attelica). Initially, the sample is incubated with acridinium-ester (AE) labeled antibodies, which bind to the NfL antigen. Following this step, paramagnetic particles (PMP) coated with capture antibody are added to the sample, forming complexes of antigen bound to AE-labeled antibodies and PMP. Unbound AE-labeled antibodies are then separated and removed, following which acid and base are added to initiate chemiluminescence and light emission is measured. All steps are performed on the fully automated Attelica immunoassay system.

Compared to other chemiluminescent technologies, AE features a number of advantages, including: 1) High quantum yields: high signal-to-noise ratio for improved sensitivity and low-end precision; 2) Rapid kinetics with light emission complete in 1-5 seconds: high throughput; 3) Hydrophilicity: improved efficacy of wash step for low non-specific binding; 4) Hydrolytic stability: long reagent shelf life and extended onboard stability; and 5) Small size: direct labeling with AE for use in a broad range of assays.

Laboratory Quality Assurance and Monitoring

The analytical measurements were conducted following strict quality control/quality assurance procedures. In addition to study samples, low, medium, and high concentration quality control (QC) samples were run each 8-hour shift as well as additional replicate samples to ensure accuracy and reliability of the derived data. We calculated the coefficient of variation (CV) and other relevant statistics to describe the QC samples across the spectrum of sNfL measures. In addition, as a part of a related study, sNfL measurement will be performed in spiked control samples and in a subset of participants (100 HC and 100 MS participants) with calculation of intra- and inter-assay coefficient of variation. These participants will be selected in part to have sNfL values that span the entire range of values observed in the overall cohort.

Data Processing and Editing

Data were received after all analyses were complete. The data were not edited. Data Access: All data are publicly available.

Analytic Notes

Subsample Weights

Subsample weights are required to analyze these data properly. Specific sample weights (WTSSNH2Y) for this subsample are included in this data file and should be used when analyzing these data. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

Detection Limits

The lower limit of quantification (LLOQ) of the assay is 3.9 pg/mL, which was determined by replicate testing (n=44) of low concentration NfL samples. The lower limit of quantification (LLOQ) was defined as the concentration at which the coefficient of variation (CV) was less than or equal to 20%.

The detection limits were constant for all of the analytes in the data set. Two variables are provided for each analyte. The variable name ending in “L” (ex., SSNFLL) indicates whether the result was below the LLOQ: the value “0” means that the result was at or above the LLOQ, “1” indicates that the result was below the LLOQ. A similar variable is ending in “H” indicates the result was above the upper limit of quantification (ULOQ) (ex., SSNFLH).

For analytes with analytic results below the LLOQ (ex., SSNFLL=1), an imputed fill value was placed in the analyte results field equal to the LLOQ divided by the √2. For analytes with analytic results above the ULOQ (ex., SSNFLH=1), an imputed fill value was placed in the analyte results field equal to the ULOQ multiplied by the √2.

The lower limit of quantification (LLOQ, in pg/mL) and upper limit of quantification (ULOQ, in pg/mL) for SSSNFL are:

Variable Name	SAS Label	LLOQ	ULOQ
SSSNFL	Serum neurofilament light chain (pg/mL)	3.9 pg/mL	500 pg/mL

Interferences:

Blanks in an analyte results field represent missing values in cases where sNfL assays did not succeed in obtaining a valid numeric result (e.g., sample quantity was not sufficient).

References

• Bacioglu M, Maia LF, Preische O, Schelle J, Apel A, Kaeser SA, et al. Neurofilament Light Chain in Blood and CSF as Marker of Disease Progression in Mouse Models and in Neurodegenerative Diseases. Neuron 2016; 91: 494–6.
• Byrne LM, Rodrigues FB, Blennow K, Durr A, Leavitt BR, Roos RAC, et al. Neurofilament light protein in blood as a potential biomarker of neurodegeneration in Huntington’s disease: a retrospective cohort analysis. Lancet Neurol 2017; 16: 601–9.
• De Marchis GM, Katan M, Barro C, Fladt J, Traenka C, Seiffge DJ, et al. Serum neurofilament light chain in patients with acute cerebrovascular events. Eur J Neurol 2018; 25: 562–8.
• Disanto G, Adiutori R, Dobson R, Martinelli V, Dalla Costa G, Runia T, et al. Serum neurofilament light chain levels are increased in patients with a clinically isolated syndrome. J Neurol Neurosurg Psychiatry 2016; 87: 126–9.
• Disanto G, Barro C, Benkert P, Naegelin Y, Schädelin S, Giardiello A, et al. Serum Neurofilament light: A biomarker of neuronal damage in multiple sclerosis. Ann Neurol 2017; 81: 857–70.
• Gunnarsson M, Malmeström C, Axelsson M, Sundström P, Dahle C, Vrethem M, et al. Axonal damage in relapsing multiple sclerosis is markedly reduced by natalizumab. Ann Neurol 2011; 69: 83–9.
• Lépinoux-Chambaud C, Eyer J. Review on intermediate filaments of the nervous system and their pathological alterations. Histochem Cell Biol 2013; 140: 13–22.
• Olsson B, Portelius E, Cullen NC, Sandelius Å, Zetterberg H, Andreasson U, et al. Association of Cerebrospinal Fluid Neurofilament Light Protein Levels With Cognition in Patients With Dementia, Motor Neuron Disease, and Movement Disorders. JAMA Neurol 2019; 76: 318–25.
• Petzold A. Neurofilament phosphoforms: surrogate markers for axonal injury, degeneration and loss. J Neurol Sci 2005; 233: 183–98.
• Preische O, Schultz SA, Apel A, Kuhle J, Kaeser SA, Barro C, et al. Serum neurofilament dynamics predicts neurodegeneration and clinical progression in presymptomatic Alzheimer’s disease. Nat Med 2019; 25: 277–83.
• Weydt P, Oeckl P, Huss A, Müller K, Volk AE, Kuhle J, et al. Neurofilament levels as biomarkers in asymptomatic and symptomatic familial amyotrophic lateral sclerosis. Ann Neurol 2016; 79: 152–8.

Codebook and Frequencies