The goal attainment scale in primary mitochondrial disease: Construct validity and lessons learned from a randomized controlled trial

GAS demonstrated some construct validity in relation to fatigue and depressive symptoms, showed limited overlap with conventional outcome measures and suffered from suboptimal implementation. Although exploratory, these findings suggest GAS may capture patient-relevant change in individuals with PMD. To realize its potential, standardized methodology and further validation are essential for its use as a robust outcome measure in future PMD trials.