Estimating the minimum important difference for the questionnaire about the Process of Recovery (QPR): an anchor-based approach

Abstract

ABSTRACT Background: Despite wide usage of the Questionnaire about the Process of Recovery (QPR), the minimum important difference (MID) for the measure has not been identified. Establishing the MID for the QPR is required in order to facilitate the interpretation of outcomes in clinical practice and the use of this scale in research, to measure meaningful change in people with psychosis. Methods: Using an anchor-based method, data from four existing trials of interventions for people with psychosis (N = 681) were used to identify the MID for the QPR. Changes in QPR total scores between baseline and end of treatment were assessed for correspondence with several anchor measures which had established MIDs or face-value clinical meaning. A range of MID values were calculated. Results: Based on anchor measures that were orientated towards service-user priorities, a within-person MID of 5 points and a between-group MID of 4 points are suggested. Results also indicated that the reliability and validity of the 15-item version of the QPR was high, which provides support for its use in clinical practice and research. Conclusions: Implications for future research and clinical practice are discussed.