Methodological Approaches to Estimating the Minimally Clinically Important Difference in Inflammatory Rheumatic Diseases: A Systematic Review

This project is a systematic review and critical appraisal of methodological approaches used to estimate the minimally clinically important difference (MCID), minimal important difference (MID), minimal important change (MIC), smallest worthwhile effect (SWE), and related constructs in inflammatory rheumatic diseases. Interpretation of patient-reported outcomes (PROMs) and clinical measures in rheumatology requires understanding what magnitude of change represents a meaningful benefit for patients. Although MCID/MID estimates are widely reported, the methods used to derive these thresholds vary substantially and are often based on anchor-based or distribution-based approaches that may not adequately reflect patient perspectives, intervention-specific benefit–harm considerations, or true between-group treatment effects. Building on conceptual work advocating patient-centred and intervention-specific definitions of clinical importance (e.g., benefit–harm trade-off approaches), this review will: Identify primary studies that estimate MCID/MID/MIC/SWE (or related constructs) in adults with inflammatory rheumatic diseases (including rheumatoid arthritis, axial spondyloarthritis, psoriatic arthritis, peripheral spondyloarthritis, Sjögren syndrome, sarcoidosis with musculoskeletal involvement, and related conditions). Systematically describe and categorize the methodological approaches used (anchor-based, distribution-based, benefit–harm trade-off, discrete choice experiments, consensus approaches, etc.). Critically evaluate whether estimates are: patient-centred (elicited directly from patients), intervention-specific (explicitly incorporating risks, costs, or inconvenience), expressed as between-group effects (with vs. without intervention) rather than within-group change. Assess the credibility of anchor-based estimates using a validated appraisal instrument (Devji et al., 2020). Summarize the distribution of estimates across diseases, outcome domains (pain, function, disease activity, fatigue, quality of life), and methods, and discuss implications for trial design and interpretation. The expected outcomes of this project are: A comprehensive mapping of how clinically important differences are currently determined in inflammatory rheumatology. Identification of methodological limitations and common sources of bias. Clarification of the extent to which current practice aligns with patient-centred, intervention-specific, and causally interpretable concepts of treatment effect. Practical recommendations for researchers designing and interpreting clinical trials in rheumatic diseases. By synthesizing and critically appraising the available evidence, this review aims to improve the conceptual and methodological foundation for determining clinically meaningful effects in rheumatology research and to promote more patient-centred and context-sensitive approaches in future trials.