Why averaging multiple MUNIX measures in the longitudinal assessment of patients with ALS?

Objective: To assess the impact of averaging multiple MUNIX trials on the follow-up of patients with amyotrophic lateral sclerosis (ALS).

Methods: We determined the percent relative change (%RC) of MUNIX, in healthy subjects and patients with ALS, by subtracting the MUNIX value in the second visit from the first. Both the mean of a set of three MUNIX (mean-MUNIX) and the first MUNIX sample (single-MUNIX) were evaluated. Then, we studied the sensitivity to detect relative changes over time and the statistical dispersion of the %RC from these two parameters.

Results: We found that the mean-MUNIX %RC has lower mean coefficient of variation than the single-MUNIX %RC in all muscles. The mean-MUNIX also resulted in more ALS patients with significant %RC, i.e., outside reference limits.

Conclusion: The mean-MUNIX resulted in less dispersed values of %RC in patients with ALS and thus, increased the precision of the technique. The mean-MUNIX resulted also in an increase in the sensitivity to track changes over time in these patients.

Significance: The mean-MUNIX should be considered in any ALS follow-up study as a more reliable approach and as a way of potentially reducing the sample size needed for the study.