Background: Patient-reported outcomes (PROs) have the function of reflecting patients’ perspectives on treatment benefits and harms. The ability to interpret and, consequently, include PROs in the decision-making process along with other patient-important outcomes relies on the understanding of what improvement or reduction in the PRO represents a change that is considered important to patients. The most common reference point for interpretation of PROs is the minimal important difference (MID), which provides a measure of the smallest change in a PRO that patients would perceive as an important benefit or harm.
Objective: To document published anchor-based MIDs associated with PRO instruments used in evaluating the effects of interventions on chronic medical and psychiatric conditions in both adult and pediatric populations.
Methods: We are currently launching a study that summarizes and appraises available methods to estimate anchor-based MIDs. We will also document all anchor-based MIDs reported for adults and pediatric populations and will develop a rating instrument to assess their credibility. We will create an inventory of available anchor-based MIDs, including the context in which they were assessed (condition/disease), and the confidence users can place in a particular MID. We will search MEDLINE, EMBASE, PsycINFO, and CINAHL (1989 to present) to identify studies addressing methods to estimate anchor-based MIDs of PRO instruments or reporting empirical ascertainment of anchor-based MIDs. Teams of two reviewers will independently screen citations identified, and extract relevant data.
Discussion: No inventory of MIDs is currently available, which means that clinicians and patients have to navigate the vast literature in order to retrieve a specific MID. Even if they find an apparently applicable MID, there is no guidance regarding the extent to which users can trust the reported MID. We will provide a summary of the available MIDs in the literature and describe their overall credibility.