Reference values for voluntary and stimulated single-fibre EMG using concentric needle electrodes: a multicentre prospective study

Abstract

Objective: The aim of this study is to establish reference values for single-fibre electromyography (SFEMG) using concentric needles in a prospective, multicentre study.

Methods: Voluntary or stimulated SFEMG at the extensor digitorum communis (EDC) or frontalis (FRO) muscles was conducted in 56-63 of a total of 69 normal subjects below the age of 60years at six Japanese institutes. The cut-off values for mean consecutive difference (MCD) of individual potentials were calculated using +2.5 SD or 95% prediction limit (one-tail) of the upper 10th percentile MCD value for individual subjects.

Results: The cut-off values for individual MCD (+2.5 SD) were 56.8μs for EDC-V (voluntary SFEMG for EDC), 58.8μs for EDC-S (stimulated SFEMG for EDC), 56.8μs for FRO-V (voluntary SFEMG for FRO) and 51.0μs for FRO-S (stimulated SFEMG for FRO). The false positive rates using these cut-off values were around 2%.

Conclusions: The +2.5 SD and 95% prediction limit might be two optimal cut-off values, depending on the clinical question. The obtained reference values were larger than those reported previously using concentric needles, but might better coincide with conventional values.

Significance: This is the first multicentre study reporting reference values for SFEMG using concentric needles. The way to determine cut-off values and the statistically correct definition of the percentile were discussed.