title: A highly sensitive electrochemiluminescence immunoassay for the neurofilament heavy chain protein.
abstract: BACKGROUND
  The loss of neurological function is closely related to axonal damage. Neurofilament subunits are concentrated in neurons and axons and have emerged as promising biomarkers for neurodegeneration. Electrochemiluminescence (ECL) based assays are known to be of superior sensitivity and require less sample volume than conventional ELISAs.
  
  
  METHODS
  We developed an ECL based solid-phase sandwich immunoassay to measure the neurofilament heavy chain protein (NfH(SMI35)) in CSF. We employed commercially available antibodies as previously used in a conventional ELISA (Petzold et al., 2003; Petzold and Shaw, 2007). The optimised and validated assay was applied in a reference cohort and defined patient groups.
  
  
  RESULTS
  Analytical sensitivity (background plus three SD) of our assay was 2.4 pg/ml. The mean intra-assay coefficient of variation (CV) was 4.8% and the inter-assay CV 8.4%. All measured control and patient samples produced signals well above background. Patients with multiple sclerosis (MS) (median 46.2 pg/ml, n=95), amyotrophic lateral sclerosis (ALS) (160.1 pg/ml, n=50), mild cognitive impairment/Alzheimer's disease (MCI/AD) (65.6 pg/ml, n=20), Guillain-Barre syndrome (GBS) (91.0 pg/ml, n=20) or subarachnoid hemorrhage (SAH) (345.0 pg/ml, n=20) had higher CSF NfH(SMI35) values than the reference cohort (27.1 pg/ml, n=73, p<0.0001 for each comparison).
  
  
  CONCLUSIONS
  The new ECL based assay for NfH(SMI35) in CSF is superior in terms of sensitivity, precision and accuracy to previously published methods (Petzold et al., 2003; Shaw et al., 2005; Teunissen et al., 2009). The improved performance and small sample volume requirement qualify this method in experimental settings and clinical trials designed to perform a number of tests on limited amounts of material.
authors.affiliation: Clinical Neuroimmunology, Neurology and Department of Biomedicine, University Hospital Basel, Switzerland. kuhlej@uhbs.ch
authors.forename: Jens
authors.initials: J
authors.lastname: Kuhle
authors.forename: Axel
authors.initials: A
authors.lastname: Regeniter
authors.forename: David
authors.initials: D
authors.lastname: Leppert
authors.forename: Matthias
authors.initials: M
authors.lastname: Mehling
authors.forename: Ludwig
authors.initials: L
authors.lastname: Kappos
authors.forename: Raija L P
authors.initials: RL
authors.lastname: Lindberg
authors.forename: Axel
authors.initials: A
authors.lastname: Petzold
mesh_terms: D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000503:physiopathology; D000690:Amyotrophic Lateral Sclerosis / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000503:physiopathology; D015415:Biomarkers / Q000032:analysis / Q000134:cerebrospinal fluid; D055664:Electrochemical Techniques / Q000379:methods; D005260:Female; D020275:Guillain-Barre Syndrome / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000503:physiopathology; D009410:Nerve Degeneration / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000503:physiopathology; D019636:Neurodegenerative Diseases / Q000134:cerebrospinal fluid* / Q000175:diagnosis* / Q000503:physiopathology; D016900:Neurofilament Proteins / Q000032:analysis* / Q000134:cerebrospinal fluid*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000503:physiopathology
chemical_list: D015415:Biomarkers; D016900:Neurofilament Proteins; C051774:neurofilament protein H