Interchangeability of the EQ-5D and the SF-6D in Long-Lasting Low Back Pain

• Published in: Value in health 2009-06, Vol.12 (4), p.606-612
• Main Authors: Søgaard, Rikke, MSc, MPH, PhD, Christensen, Finn Bjarke, MD, PhD, DMSc, Videbæk, Tina Senholt, MD, Bünger, Cody, MD, DMSc, Christiansen, Terkel, MSc
• Format: Article
• Language: English
• Subjects: Adult; Aged; Assessment; Cost analysis; Cross-Sectional Studies; Decision Making; EQ-5D; Female; Health Status; Health Status Indicators; health-related quality of life; Humans; Instruments; Internal Medicine; Linear Models; Low back pain; Low Back Pain - surgery; Lumbar Vertebrae - surgery; Male; Middle Aged; Models, Statistical; Outcome Assessment (Health Care) - methods; Outcome Assessment (Health Care) - statistics & numerical data; Patient Preference; Psychometrics; Quality of Life; SF-6D; Short forms; Spinal Fusion; Time Factors; Young Adult
• ISSN: 1098-3015; 1524-4733
• DOI: 10.1111/j.1524-4733.2008.00466.x

Abstract Objectives The objective of this study was to investigate the interchangeability of the EuroQol 5D (EQ-5D) and the Short Form 6D (SF-6D) in individuals with long-lasting low back pain to guide the optimal choice of instrument and to inform decision-makers about any between-measure discrepancy, which require careful interpretation of the results of cost-utility evaluations. Methods A cross-sectional study was conducted across 275 individuals who had spinal surgery on indication of chronic low back pain. EQ-5D and SF-6D were mailed to respondents for self-completion. Statistical analysis of between-measure agreement (using English weights) was based on Bland and Altman's limits of agreement and a series of linear regressions. Results A moderate mean difference of 0.085 (SD 0.241) was found, but because it masked more severe bidirectional variation, the expected variation between observations of EQ-5D and SF-6D in future studies was estimated at 0.546. The EQ-5D's N3 term alone explained a factor of 0.79 of the variation in between-measure differences, while the explanatory value of adding variables of age, sex, diagnosis, previous surgery, and occupational status was basically zero. A final model including only dummy variables for the N3 term and five identified framing effects explained a factor of 0.86 of the variation in between-measure differences. Conclusions Although the EQ-5D and the SF-6D are both psychometrically valid for generic outcome assessment in long-lasting low back pain, it appears that they cannot generally be used interchangeably for measurement of preference values. Sensitivity analysis examining the impact of between-measure discrepancy thus remains a necessary condition for the interpretation of the results of cost-utility evaluations.