Abstract
BACKGROUND: This study aimed to evaluate clinically relevant improvement after conservative self-management of urinary incontinence via a mobile app. It further aimed to establish Minimum Important Differences (MIDs) based on the severity and type of urinary incontinence. METHODS: Data was collected in a prospective cohort study that evaluated the freely available app Tät®. The app provided pelvic floor muscle training (PFMT) and life-style advice. Non-pregnant, non-postpartum women (≥ 18 years) who downloaded the app to treat urinary incontinence were included, if they completed the Patient Global Impression of Improvement (PGI-I) question at the 3-month follow-up (n = 1,733). Participants answered the International Consultation on Incontinence Questionnaire (ICIQ-UI SF) at baseline and after 3 months. The score change was analysed for correlation (Spearman) with the PGI-I. We then analysed one-way ANOVAs to determine whether there were significant differences between the groups based on the answers to the PGI-I. The MID was set to the mean change of the group that selected the answer "a little better" to the PGI-I question. RESULTS: The one-way ANOVA showed significant differences between PGI-I groups (p < 0.001). The MID for the general group was set to 1.46 (95% Confidence Interval [CI] 1.26-1.67). In the sub-group analyses, a MID for the group with slight incontinence could not be determined. For the group with moderate severity the MID was determined to be 1.33 (95% CI 1.10-1.57) and for the severe/very severe group it was 3.58 (95% CI 3.08-4.09). Analysis of different types of incontinence showed no difference in MIDs. CONCLUSIONS: The MID for self-management via a mobile app was lower than previously established MIDs, but differed depending on baseline severity. This study shows that MIDs need adjustment for baseline severity and treatment intensity when interpreting clinical trial results. If using MIDs as exact numbers, the study population and the treatment must be comparable.