Reliability and Validity of the Japanese Version of the Multidimensional Evaluation Scale for Patient Impression Change (MPIC): A Brief Tool for Multidimensional Assessment in Interdisciplinary Pain Management

<b>Background:</b> Chronic pain significantly impacts quality of life and may lead to physical and psychological dysfunction. Although various tools have been developed to assess pain-related conditions, many are composed of time-consuming multi-item questionnaires, limiting practicality in clinical settings. The Multidimensional Evaluation Scale for Patient Impression of Change (MPIC) was developed as a simple, retrospective tool to assess multiple domains targeted in interdisciplinary pain management. This study evaluated the reliability and validity of the Japanese MPIC in patients with chronic non-cancer pain. <b>Methods:</b> We recruited 101 participants from the Interdisciplinary Pain Center at Keio University Hospital between August 2022 and September 2024. Pretreatment measures included pain intensity, disability, catastrophizing, self-efficacy, psychological distress, and sleep quality. Baseline assessments encompassed pain intensity, disability, catastrophizing, self-efficacy, psychological distress, and sleep quality. Psychological distress was evaluated using the Hospital Anxiety and Depression Scale (HADS) for the initial cohort of 35 participants and the Kessler Psychological Distress Scale (K6) for the subsequent 66 participants. Following the intervention, participants completed the MPIC, in addition to reassessments of pain intensity, disability, catastrophizing, self-efficacy, psychological distress (HADS or K6), and sleep quality. Retesting the MPIC was performed in a small subgroup of 20 participants for test-retest reliability analysis. Confirmatory factor analysis (CFA), average variance extracted (AVE), Pearson's correlations with pain-related measures, Cronbach's alpha, and intraclass correlation coefficients (ICC) were used to assess construct validity, convergent validity, criterion validity, internal consistency, and reliability. <b>Results:</b> CFA indicated marginal fit (CFI = 0.86, RMSEA = 0.23, SRMR = 0.06), with factor loadings from 0.49 to 0.91. AVE supported convergent validity (0.58). Internal consistency was excellent (Cronbach's alpha = 0.93), and ICC was moderate (0.52). MPIC domains correlated significantly with changes in pain intensity, disability, catastrophizing, self-efficacy, sleep, and psychological distress (<i>p</i> < 0.05), supporting criterion validity. <b>Conclusions:</b> The Japanese MPIC provides preliminary evidence of validity and reliability, with acceptable internal consistency, marginal structural fit, and moderate test-retest reliability. These findings suggest that the MPIC may serve as a concise retrospective instrument for assessing multidimensional treatment outcomes within interdisciplinary pain management programs for chronic non-cancer pain.