Qualiveen, a urinary-disorder specific instrument: 0.5 corresponds to the minimal important difference

This study assessed the interpretability of changes in Qualiveen, a specific health-related quality-of-life (HRQOL) questionnaire for urinary disorders (UD) in multiple sclerosis (MS) patients. Qualiveen has 30 items focusing on four aspects of patients' lives related to their urinary problems: bother with limitations (nine items), frequency of limitations (eight items), fears (eight items), and feelings (five items). Response options are framed as 5-point Likert-type scales, and scores on each domain range from 0 to 4.

One hundred twenty-one MS patients with UD completed Qualiveen at baseline and 2-10 weeks later. At the second visit, patients also made global ratings of change in urinary HRQOL (GRC) with a 15-point scale from -7 to +7. We addressed the validity of GRC by examining its relationships with pre- and post-Qualiveen scores and determined the mean change in score on each Qualiveen domain associated with small, moderate, and large changes in the corresponding GRC.

The correlation of the change score with the corresponding GRC was substantially stronger than the correlation with either pre- or post-Qualiveen score, establishing the validity of the GRC. In all domains, a within-patient change in Qualiveen score of approximately 0.5 (range: 0.36-0.72) represents the minimal important difference. A change in score of approximately 0.7 corresponds to a moderate change in quality of life (range: 0.55-0.86).

These estimates will help in interpreting the results of subsequent studies that use Qualiveen to examine the impact of interventions designed to improve urinary-specific HRQOL.