Psychometric performance of the Primary Mitochondrial Myopathy Symptom Assessment (PMMSA) in a randomized, double-blind, placebo-controlled crossover study in subjects with mitochondrial disease.

Upon evaluation of its psychometric properties, the PMMSA, specifically the 4FS domain, demonstrated strong reliability and construct-related validity. The PMMSA can be used to evaluate treatment benefit in clinical trials with individuals with PMM. Trial registration ClinicalTrials.gov identifier, NCT02805790; registered June 20, 2016; https://clinicaltrials.gov/ct2/show/NCT02805790 .