Exploring the Stability of Communicative Participation and Level of Daily Speech Usage Among Individuals With Hypophonia and Parkinson's Disease.

Purpose: This exploratory study evaluated the test-retest stability of three participation-based patient-reported outcome measures (PROMs) rated by individuals with Parkinson's disease (IWPD), primary communication partners (PCPs) serving as proxy raters, and control participants over three study visits spanning approximately 1 month.

Method: Twenty-three IWPD and hypophonia, 23 PCPs, and 30 control participants attended three non-intervention experimental visits. During each visit, all participants completed three participation-based PROMs: Communicative Participation Item Bank (CPIB), Voice Activity and Participation Profile (VAPP), and Levels of Speech Usage Scale (LSUS). Proxy ratings for each PROM were completed by PCPs.

Results: Results indicated significant differences between IWPD and control participants on all PROMs. IWPD exhibited lower scores on the CPIB and LSUS and higher scores on the VAPP compared to control participants. There was relative agreement in ratings between IWPD and their PCPs on all PROMs. Finally, there were relatively stable test-retest scores on all three PROMs over the three study visits, both within and between IWPD and PCPs. An exception was a statistically, but not clinically significant, decrease in CPIB scores between Visit 1 and Visit 3 for IWPD.

Conclusions: This study has contributed to our understanding of the measurement properties of the CPIB, VAPP, and LSUS related to the test-retest stability of these measures over three time points in IWPD, proxy raters, and control participants. These findings provide additional context in the interpretation of participation-based PROMs in this clinical population and may prove to be useful in interpreting changes to participation-based PROM scores.