Psychometric properties of the EQ-5D-5L in patients with hip or knee osteoarthritis: reliability, validity and responsiveness
To study the psychometric properties, including reliability, validity and responsiveness, of the Spanish EQ-5D-5L questionnaire for patients with hip or knee osteoarthritis (OA).
We included 758 patients with hip or knee OA who completed the EQ-5D-5L and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at baseline, of whom 644 also did 6 months later. The EQ-5D-5L contains five questions from which a utility index is derived. The WOMAC covers three dimensions: pain, stiffness and physical function. Floor and ceiling effects were calculated. Reliability was assessed using Cronbach’s alpha. Convergent validity was tested using the Spearman correlation coefficient between EQ-5D-5L and WOMAC. We examined known-groups validity by comparing the EQ-5D-5L between subgroups defined by WOMAC scores using ANOVA or the Kruskal–Wallis test. Effect sizes were calculated to assess responsiveness, and minimal clinically important difference (MCID) was estimated.
The EQ-5D-5L showed minimal floor and ceiling effects (< 3%). Cronbach’s alpha was 0.86. The EQ-5D-5L index was strongly correlated with WOMAC pain and function scores (− 0.688 and − 0.782). Patients with higher WOMAC scores had significantly (p < 0.0001) lower EQ-5D-5L index. The 20.19% had hip or knee replacement during the follow-up. Effect sizes were small among non-surgical patients, but > 0.80 among “improved” surgical patients, being the MCID for improvement 0.32 points.
The results support the reliability, validity and responsiveness of the EQ-5D-5L, overcoming the limitations of the EQ-5D-3L in these patients. Therefore, the EQ-5D-5L could be very useful as an outcome measure, at least in patients with hip or knee OA.
KeywordsEQ-5D-5L Osteoarthritis Utility index Psychometric properties Minimal clinically important difference
We are grateful to colleagues in the participating hospitals and primary care centres for their support and to all patients for their collaboration. We acknowledge the help provided by the Biostatistics Research Group (Biostit), supported by the Department of Education, Linguistics Policy and Culture of the Basque Government (Ref: IT620-13). We also acknowledge the editorial assistance provided by Ideas Need Communicating Language Services, through the translation and edition service of the Basque Foundation for Health Innovation and Research (BIOEF).
This study was supported in part by grants from the Carlos III Health Institute (PI13/00560, PI13/00518 and PI13/00648) and the European Regional Development Fund.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study received the approval of the following Ethics Committees for Clinical Research: ECCR of Euskadi (PI2014050), Hospital Fundación Jiménez Díaz (PIC 80/2013_HRJC), Hospital Universitario de Fuenlabrada (APR 14–27), Hospital Universitario Fundación Alcorcón (14/19), Hospital Universitario de Canarias (2014–109) and Hospital Universitario Nuestra Señora de Candelaria (PI-09/15).
Informed consent was obtained from all individual participants included in the study.
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