The Performance Scales disability measure for multiple sclerosis: use and sensitivity to clinically important differences

BACKGROUND: In 1993, the Performance Scales© was created to assess multi-dimensional disability in multiple sclerosis (MS). This tool has been used in a variety of settings and study designs internationally. The present work provides an overview of the history and psychometric characteristics of the Performance Scales©, reviews its use over the past two decades, and summarizes its responsiveness to subgroup differences. METHODS: A Google Scholar and Ovid search yielded 230 articles citing the Performance Scales©, of which 82 studies used the tool in empirical research. Twelve articles provided sufficient information to enable computation of effect sizes. Forest plots were used to show effect sizes for the overall summary score and by domain by patient demographics, MS disease trajectory, and treatment adherence. RESULTS: The Performance Scales© evidenced sensitivity to clinically important differences by disease trajectory and age (for selected domains). In contrast, groups distinguished by patient adherence to disease-modifying therapies and ethnicity were relatively small. CONCLUSIONS: The Performance Scales© has been used in a large number of studies since its development, suggesting that this psychometrically sound tool is acknowledged to be a useful tool for MS clinical research. It is recommended that future work include the entire measure, so that the whole-person impact of MS can be characterized and considered in MS outcome research.