Objectives: Thresholds for the minimally important difference (MID) or responder definition (RD) in health-related quality-of-life (HRQoL) scores are required to interpret the impact of an intervention or change in the trajectory of the condition which is meaningful to patients. This study aimed to establish MID and RD for the European Organisation for Research and Treatment of Cancer Quality of Life Multiple Myeloma questionnaire (EORTC QLQ-MY20).Methods: A novel mixed-methods approach was applied by utilizing both existing clinical trial data and prospective patient interviews. Anchor-based, distributionbased, and qualitative-based estimates of meaningful change were triangulated to form recommended RDs for each scale of the EORTC QLQ-MY20. Anchor-based MIDs were summarized using weighted correlation.Results: Recommended MIDs were as follows: Disease Symptoms (DS 10 points), Side Effects of Treatment (SE 10 points), Body Image (BI 13 points), and Future Perspective (FP 9 points). Recommended RDs were as follows: DS (16 improvement; 11 worsening), SE (6 improvement; 9 worsening), BI (33 improvement; 33 worsening), and FP (11 improvement; 11 worsening).
Conclusions:The study generated estimates of the MID and RD for each scale of the EORTC QLQ-MY20. Published estimates will enable investigators and clinicians to adopt these as standard for interpretation and for hypothesis testing. Consequently, analyses from trials of different interventions can be more comparable.
K E Y W O R D SEORTC QLQ-MY20, interpretation guidelines, meaningful change, minimally important difference, mixed methods, multiple myeloma, qualitative interviews, quality of life, responder definition Kate Sully and Andrew Trigg are contributed equally to this work.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.