6 research outputs found
Quality Control of Motor Unit Number Index (MUNIX) Measurements in 6 Muscles in a Single-Subject âRound-Robinâ Setup
Background
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.
Objective
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.
Methods
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.
Results
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.
Conclusion
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