Development and validation of a disease-specific health-related quality of life measure, the LupusQol, for adults with systemic lupus erythematosus

Abstract

Objective: To develop and validate a disease-specific health-related quality of life (HRQOL) instrument for adults with systemic lupus erythematosus (SLE).

Methods: The work consisted of 6 stages. Stage 1 included item generation for questionnaire content from semistructured interviews with SLE patients. In stage 2 item selection for the draft questionnaire was performed by thematic analysis of the patient interview transcripts and expert panel agreement. In stage 3 the content validity of the draft questionnaire was assessed by patients completing the questionnaire and providing critical feedback. In stages 4 and 5 construct validity and internal reliability of the 3 versions of the LupusQoL were evaluated using principal component analysis with varimax rotation and Cronbach's alpha coefficients, respectively. In stage 6 discriminatory validity, concurrent validity, and test-retest reliability were evaluated.

Results: Stages 1, 2, and 3 resulted in a preliminary instrument containing 63 items. In stage 4, 8 domains were identified. This factor structure, accounting for 82% of the variance, was confirmed in stage 5. The domains and Cronbach's alpha coefficients were physical health (0.94), emotional health (0.94), body image (0.89), pain (0.92), planning (0.93), fatigue (0.88), intimate relationships (0.96), and burden to others (0.94). Discriminant validity was demonstrated for different levels of disease activity (British Isles Lupus Assessment Group Index) and damage (Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index). High correlations (r = 0.71-0.79) between comparable domains of the Short Form 36 and the LupusQoL assured acceptable concurrent validity. Good test-retest reliability (r = 0.72-0.93) was demonstrated.

Conclusion: The LupusQoL is a validated SLE-specific HRQOL instrument with 34 items across 8 domains defined by patients as being important.