Details

Autor(en) / Beteiligte

• Khanna, Dinesh
• Furst, Daniel E.
• Wong, Weng Kee
• Tsevat, Joel
• Clements, Philip J.
• Park, Grace S.
• Postlethwaite, Arnold E.
• Ahmed, Mansoor
• Ginsburg, Shaari
• Hays, Ron D.

Titel

Reliability, Validity, and Minimally Important Differences of the SF-6D in Systemic Sclerosis

Ist Teil von

• Quality of life research, 2007-08, Vol.16 (6), p.1083-1092

Ort / Verlag

Netherlands: Springer

Erscheinungsjahr

2007

Link zum Volltext

Quelle

Psychology & Behavioral Sciences Collection

Beschreibungen/Notizen

• Objectives To evaluate the reliability and validity and estimate the minimally important difference (MID) for the SF-6D in patients with systemic sclerosis (SSc). Subjects We used data from two clinical studies to analyze the SF-6D in patients with SSc: Study 1 was a cross-sectional observational study (N = 107) designed to assess three direct preference measures—the rating scale, time trade-off, and standard gamble (SG) in patients with diffuse SSc and limited SSc, and Study 2 was a 12-month randomized, clinical trial (N = 168) assessing oral bovine collagen versus placebo in diffuse SSc. Methods We assessed the test-retest reliability of the SF-6D in Study 2 over a mean (SD) 4.8 (3.0)-week interval and the agreement between the SF-6D and direct preference measures in Study 1 using intraclass correlations (ICC). The MID was estimated using three different anchors—the SF-36 change in health item (patients who answered "somewhat better" formed the MID group), the Health Assessment Questionnaire-Disability Index (HAQDI; change of ≥0.14 and ≥0.22) and the skin score (change of ≥5.3). Results The mean (SD) SF-6D scores were 0.61 (0.12) in Study 1 and 0.64 (0.13) in Study 2. Test-retest reliability for the SF-6D was high (ICC = 0.82 [95% CI: 0.76, 0.87]). Agreement between the SF-6D and three direct preferences measures was poor to moderate (0.16—0.52). The MID estimate for the SF-6D using the change in SF-36 item -0.012 and this level of change was similar to the no change group. The mean MID estimate for the SF-6D improvement using the HAQ-DI and skin score as anchors was 0.035 (effect size of 0.27). Conclusion This is the first study to assess the SF-6D in SSc. The SF-6D is reliable and valid in patients with SSc. We provide MID estimates that can aid in calculating sample size for clinical trials involving patients with diffuse SSc.