Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Validation of the SF-6D Utility Measure in Patients with Systemic Lupus Erythematosus (SLE).

Harrison5,  Mark J., Dale1,  Nicola, Haque2,  Sahena, Shelmerdine6,  Joanna, Teh4,  Lee-Suan, Ahmad3,  Yasmeen, Bruce1,  Ian N.

Arthritis Research UK Epidemiology Unit, The University of Manchester, Manchester, United Kingdom
Arthritis Research UK Epidemiology Unit, The University of Manchester, Manchester, United Kingdom
Betsi Cadwaladr University Health Board-West, Rheumatology, Llandudno, United Kingdom
Department of Rheumatology, Royal Blackburn Hospital, Blackburn, United Kingdom
Health Sciences Research Group, The University of Manchester, Manchester, UK
The Kellgren Centre for Rheumatology, Central Manchester Foundation Trust, Manchester, UK

Purpose:

Collection of health-related quality of life (HRQoL) questionnaire with sets of utility values, such as the SF-6D, allow quality-adjusted life years used in cost-utility evaluations to be calculated. However these measures should be evaluated for validity in each setting they are applied. Few studies in systemic lupus erythematosus (SLE) have included a generic HRQoL measure; therefore the validity of these measures for this setting is unclear. This study aims to explore the construct validity and the minimum important difference (MID) of the SF-6D in SLE patients.

Methods:

Female patients with SLE (>=4 ACR criteria) were recruited from routine outpatient clinics at 2 time points 5 years apart. At baseline and 5 years patients had a clinical assessment including the SLEDAI 2000 and SLICC damage index. Patients also completed the generic RAND Medical Outcome Study 36-Item Short-Form Survey version 1 (MOS SF-36), which allows the SF-6D to be calculated, at baseline and 5-years and the (disease specific) LupusQoL® was completed at the 5-year time point.

Construct validity was tested by (1) correlation (Pearson) of SF-6D with SLICC (damage), SLEDAI (activity), patient characteristics (age, disease duration, education, smoking, depression, fatigue), and LupusQoL® (at 5-years). The ability to discriminate between groups was tested using the t-test. The minimum important difference (MID) was estimated in two ways: (1) multiplying the SF-6D standard deviation by a small effect size (0.2), and (2) regressing the SF-6D onto SLICC to estimate the change associated with change equivalent to the MID of SLICC.

Results:

181 patients (mean age 48 years, mean disease duration 11 years) had SF-6D scores at baseline; the mean SF-6D score was 0.60 (0.12). The SF-6D correlated more strongly with age (-0.19) and SLICC (-0.24) than disease duration (-0.04), education (0.08) or SLEDAI (-0.06). In 113 patients with an SF-6D calculated score at 5-years, the correlation of the SF-6D with LupusQoL® domains was 0.6–0.8 for all domains apart from intimacy (0.44) and body image (0.36) The SF-6D could distinguish between those who smoked (-0.07, p=0.003), had carotid plaque (-0.05, p=0.027), had depression (-0.09, p<0.001), and reported fatigue (-0.06, p=0.006), from those who did not. The MID was estimated to be 0.024 to 0.028.

Conclusions:

The SF-6D is valid for the measurement of HRQoL in patients with SLE; the measure reflects a number of key outcomes of the disease. Low correlation with aspects of intimate relationships and body image represents a concern and reinforces the need for collecting disease-specific measures of HRQoL alongside generic measures. The MID for the SF-6D is 0.024–0.028, smaller than estimates for other rheumatic disease such as rheumatoid arthritis.

To cite this abstract, please use the following information:
Harrison, Mark J., Dale, Nicola, Haque, Sahena, Shelmerdine, Joanna, Teh, Lee-Suan, Ahmad, Yasmeen, et al; Validation of the SF-6D Utility Measure in Patients with Systemic Lupus Erythematosus (SLE). [abstract]. Arthritis Rheum 2010;62 Suppl 10 :795
DOI: 10.1002/art.28563

Abstract Supplement

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