Responsiveness and minimal important score differences in quality-of-life questionnaires: a comparison of the EORTC QLQ-C30 cancer-specific questionnaire to the generic utility questionnaires EQ-5D and 15D in patients with multiple myeloma Ann Kristin Kvam 1,2,3 , Peter M. Fayers 4,5 , Finn Wisloff 1,2 1 Department of Haematology, Oslo University Hospital, Ullevaal; 2 Faculty of Medicine, University of Oslo, Oslo; 3 Akershus University Hospital, Lørenskog, Norway; 4 Division of Applied Health Sciences, University of Aberdeen, Aberdeen, UK; 5 Pain and Palliation Research Group, Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway Multiple myeloma (MM) is an incurable, malignant dis- ease of the bone marrow with an expected median sur- vival of approximately 5 yr (1). Patients with MM often have pronounced symptoms, and in the absence of a curative treatment, an important aim of the therapy is to improve the patients’ quality of life. Consequently, health-related quality of life (HRQOL) has become an increasingly important outcome in the treatment of patients with myeloma (2). HRQOL can be measured by using generic and dis- ease-specific questionnaires. While generic questionnaires focus on broad aspects of HRQOL and are intended for general use irrespective of the disease of the patient, disease-specific questionnaires are developed to detect disease- and treatment-related effects (3). A particular group of generic questionnaires are the utility question- naires which are used for the economic evaluation of healthcare interventions. These questionnaires are used Abstract Objectives: The aims of this study were to (i) compare the responsiveness of the EORTC QLQ-C30 can- cer-specific questionnaire and the generic questionnaires EQ-5D and 15D used for economic evaluation of healthcare interventions and (ii) determine the minimal important differences (MIDs) in these question- naires. The MID is the smallest change in a quality-of-life score considered important to patients. Methods: Between 2006 and 2008, 239 patients with multiple myeloma completed the questionnaires at inclusion (T1) and after 3 months (T2). At T2, patients were asked whether they had noticed any change in their quality of life. Responsiveness and MIDs were determined by mean score changes (T2–T1) for patients who, in the interview, stated they had improved, deteriorated, or were unchanged. Responsiveness was also assessed using standardized response means. Wilcoxon tests for pair differences were used to evalu- ate the statistical significance of the changes. Results: Patients who improved had significantly (P < 0.01) higher scores at T2 in all three questionnaires. Patients who deteriorated reported lower scores at T2; however, for the 15D, the differences in score were not statistically significant. The MIDs for the QLQ- C30, EQ-5D, and 15D were 8, 0.08, and 0.03 in patients who improved and 12, 0.10 and 0.02 in patients who deteriorated, respectively. Conclusions: All three questionnaires showed an acceptable responsive- ness in patients who improved. However, the 15D did not respond optimally in patients who deteriorate and cannot be recommended for use in patients with myeloma. Key words multiple myeloma; health-related quality of life; responsiveness; minimal important difference; EORTC QLQ-C3O; EQ-5D; 15D Correspondence Ann Kristin Kvam, Department of Haematology, Oslo University Hospital, Ullevaal, 0407 Oslo, Norway. Tel: +47 41 92 72 52; Fax: +47 23 01 62 11; e-mail: a.k.kvam@medisin.uio.no Accepted for publication 8 June 2011 doi:10.1111/j.1600-0609.2011.01665.x ORIGINAL ARTICLE European Journal of Haematology 87 (330–337) 330 ª 2011 John Wiley & Sons A/S