title: Quality Control of Motor Unit Number Index (MUNIX) Measurements in 6 Muscles in a Single-Subject "Round-Robin" Setup.
abstract: Motor Unit Number Index (MUNIX) is a neurophysiological measure that provides an index of the number of lower motor neurons in a muscle. Its performance across centres in healthy subjects and patients with Amyotrophic Lateral Sclerosis (ALS) has been established, but inter-rater variability between multiple raters in one single subject has not been investigated.
  
  
  
  To assess reliability in a set of 6 muscles in a single subject among 12 examiners (6 experienced with MUNIX, 6 less experienced) and to determine variables associated with variability of measurements.
  
  
  
  Twelve raters applied MUNIX in six different muscles (abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps brachii (BB), tibialis anterior (TA), extensor dig. brevis (EDB), abductor hallucis (AH)) twice in one single volunteer on consecutive days. All raters visited at least one training course prior to measurements. Intra- and inter-rater variability as determined by the coefficient of variation (COV) between different raters and their levels of experience with MUNIX were compared.
  
  
  
  Mean intra-rater COV of MUNIX was 14.0% (±6.4) ranging from 5.8 (APB) to 30.3% (EDB). Mean inter-rater COV was 18.1 (±5.4) ranging from 8.0 (BB) to 31.7 (AH). No significant differences of variability between experienced and less experienced raters were detected.
  
  
  
  We provide evidence that quality control for neurophysiological methods can be performed with similar standards as in laboratory medicine. Intra- and inter-rater variability of MUNIX is muscle-dependent and mainly below 20%. Experienced neurophysiologists can easily adopt MUNIX and adequate teaching ensures reliable utilization of this method.
authors.affiliation: Neuromuscular Diseases Unit / ALS Clinic, Kantonsspital St.Gallen, St.Gallen, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Neuwirth
authors.affiliation: Neuromuscular Diseases Unit / ALS Clinic, Kantonsspital St.Gallen, St.Gallen, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Burkhardt
authors.affiliation: Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England.
authors.forename: James
authors.initials: J
authors.lastname: Alix
authors.affiliation: Department of Neurosciences, Hospital de Santa Maria, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Castro
authors.affiliation: Department of Neurosciences, Hospital de Santa Maria, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.
authors.forename: Mamede
authors.initials: M
authors.lastname: de Carvalho
authors.affiliation: Department of Neurology, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Gawel
authors.affiliation: Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, Utrecht, The Netherlands.
authors.forename: Stephan
authors.initials: S
authors.lastname: Goedee
authors.affiliation: Hans-Berger Department of Neurology, University Hospital Jena, Jena, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Grosskreutz
authors.affiliation: Département de Neurophysiologie, Groupe hospitalier Pitié-Salpêtrière, APHP, Paris, France.
authors.forename: Timothée
authors.initials: T
authors.lastname: Lenglet
authors.affiliation: ALS Center of Torino, Department of Neuroscience "Rita Levi Montalcini", University of Torino, Torino, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Moglia
authors.affiliation: Trinity College Biomedical Science Institute (TBSI) and Beaumont Hospital, Dublin, Ireland.
authors.forename: Taha
authors.initials: T
authors.lastname: Omer
authors.affiliation: Department of Neurology, University Hospital Leuven, Leuven, Belgium.
authors.forename: Maarten
authors.initials: M
authors.lastname: Schrooten
authors.affiliation: Neuromuscular Diseases Unit / ALS Clinic, Kantonsspital St.Gallen, St.Gallen, Switzerland.|Department of Neurology, University Hospital Basel, Basel, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Weber
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis; D004576:Electromyography / Q000379:methods* / Q000592:standards*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D009468:Neuromuscular Diseases / Q000175:diagnosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity