PT  - JOURNAL ARTICLE
AU  - Annelies Boonen
AU  - Désirée van der Heijde
AU  - Robert Landewé
AU  - Astrid van Tubergen
AU  - Herman Mielants
AU  - Maxime Dougados
AU  - Sjef van der Linden
TI  - How do the EQ-5D, SF-6D and the well-being rating scale compare in patients with ankylosing spondylitis?
AID  - 10.1136/ard.2006.060384
DP  - 2007 Jun 01
TA  - Annals of the Rheumatic Diseases
PG  - 771--777
VI  - 66
IP  - 6
4099  - http://ard.bmj.com/content/66/6/771.short
4100  - http://ard.bmj.com/content/66/6/771.full
SO  - Ann Rheum Dis2007 Jun 01; 66
AB  - Purpose: To compare aspects of validity of EuroQol—5 Dimensions (EQ-5D) and Short-Form—6 Dimensions (SF-6D), two indirect utility instruments, and the well-being rating scale (RS) in ankylosing spondylitis (AS).Methods: EQ-5D, SF-6D and RS were available for 254 patients fulfilling modified New York criteria. 134 patients were part of an observational cohort and 120 were part of a randomised controlled trial (RCT). Aspects of validity assessed were truth (agreement and correlation with external health measures) and discrimination (differentiation between health states, repeatability and detection of treatment effect).Results: Median (range) values were 0.69 (−0.08–1.00) for the EQ-5D, 0.65 (0.35–0.95) for the SF-6D and 0.65 (0.14–1.00) for the RS. Agreement (intraclass correlation coefficient) was moderate (0.46–0.55). Instruments correlated equally with disease activity, functioning and quality of life. The SF-6D showed smaller average differences in utility between patients with better and worse disease compared with the EQ-5D and the RS. The smallest detectable difference (SDD) (in the control group of RCT) was 0.36, 0.17 and 0.33 for EQ-5D, SF-6D and RS, respectively. The ability to detect treatment effect (in the intervention trial) showed standardised effect sizes that were moderate for EQ-5D and SF-6D (0.63 and 0.64) and low for the RS (0.23).Conclusion: In patients with AS, EQ-5D, SF-6D and the RS correlate equally well with external measures of health, but have different psychometric properties. The SDD is most favourable for the SF-6D, but it discriminates less well between patients with different disease severities. The RS has a poorer ability to detect treatment effects. It is difficult to recommend one of the instruments.