Background: The minimal important difference (MID) is used to determine whether a treatment is clinically relevant to different stakeholders, especially patients. This is relevant for decision-making since MIDs can be used to determine effective treatments. There is a lack of evidence regarding MIDs related to female urinary incontinence (UI) outcomes, which might negatively impact clinical decision-making.
Objectives: We aimed to synthesize the distribution and anchor-based methods to estimate the MIDs for outcome measures related to UI.
Methods: This systematic review was registered in PROSPERO (protocol CRD42022299686). Searches were performed on Medline, Embase, CINAHL, Web of Science, and Scopus on June 2021 and were updated on October 2022. Studies that provided MID according to distribution- or anchor-based methods for patient-reported outcome measures related to female UI outcomes were included. The credibility and certainty of the evidence were assessed for anchor-based methods. When possible, absolute minimal important differences were calculated for each study separately according to the mean change of the group of participants that slightly improved.
Results: Eleven studies were included. Twelve questionnaires commonly used for assessing urinary symptoms and their respective MIDs were included. Both distribution and anchor-based MIDs were compiled. Most of the MIDs derived from anchor-based methods did not consider the smallest difference identified by the participants to calculate the MID. This means that the available literature misused and misinterpreted the concept of MID. All reports related to anchor-based methods presented low credibility and very low certainty of the evidence.
Conclusions: There is a high variability around the minimal important difference related to patient-reported outcome measures for UI outcomes (method of analysis, questionnaires, and anchors used). In addition, the credibility and certainty of the evidence to support these MIDs are still limited.
Patient, public and/or healthcare consumer involvement: The result of this review highlight the importance of developing better evaluation measurement tools, with better pre-established MIDs, so more accurate results could be found to determine the effectiveness of the treatment, consequently helping the clinical practice evaluation.