The minimal important difference (MID) on patient-reported outcome measures can indicate how much of a change on that scale is meaningful.Objective
To use an anchor-based approach to estimate MID in the Voice Handicap Index–10 (VHI-10) total score.Design, Setting, and Participants
In this cohort study, a volunteer sample of adult patients visiting the voice clinic at the University of Minnesota from April 7, 2013, through July 3, 2016, completed the VHI-10 (range, 0-40, with higher scores indicating greater voice-related handicap) at baseline and 2 weeks later in conjunction with a global rating of change. An anchor-based approach was used to identify an MID. The association between the global change score and change in VHI-10 score was analyzed using Pearson rank correlation. A distribution-based method was used to corroborate the findings.Main Outcome and Measures
Global rating of change on the VHI-10.Results
Of the 273 participants, 183 (67.0%) were women and 90 (33.0%) were men (mean [SD] age, 54.3 [15.6] years); 259 (94.9%) were white. Participants had a variety of voice disorders, most commonly muscle tension dysphonia, irritable larynx, benign vocal fold lesions, and motion abnormalities. Among patients reporting no change on the global change score, the mean (SD) change in VHI-10 score was 1 (5). Among those reporting a small change, the mean (SD) change in VHI-10 was also 1 (5). Among those reporting a moderate change in voice symptoms, the mean (SD) change in VHI-10 score was 6 (8). Among those with a large change, the mean (SD) change in VHI-10 score was 9 (13). The correlation between the global change score and the change in VHI-10 score was 0.32 (95% CI, 0.12-0.49). Distribution-based analyses identified effect sizes comparable to those of the anchor-based categories.Conclusions and Relevance
These findings suggest that a difference of 6 on the VHI-10 may represent an MID. This difference was associated with a moderate change on the global rating scale, and the small-change and no-change categories were indistinguishable. Given the lack of differentiation between small and no change and the modest correlation between the global change score and change in the VHI-10 score, additional studies are needed.