Patient-reported outcomes are valuable for management of chronic diseases like Systematic Lupus Erythematosus (SLE), but no measures to our knowledge have been validated for use in US-based SLE patients.
Objectives: To adapt and assess the validity and reliability of an SLE-specific quality of life (QoL) measure developed in the United Kingdom, the LupusQoL©, for use in US-based SLE patients.
Methods: Debriefing interviews of SLE subjects guided the language modifications of the tool. The LupusQol-US©, SF-36 and EQ5D were administered. Internal consistency (ICR) and test-retest (TRR) reliability, convergent and discriminative validity were examined. Factor analyses were performed.
Results: The mean (SD) age of the 185 SLE subjects was 42.5± 12.9 years. ICR and TRT of the 8 domains ranged from 0.85 to 0.94 and 0.68-0.92 respectively. Related domains on the SF-36 correlated with the LupusQoL© domains (Physical Health and Physical Function r= 0.73, Physical Health and Role Physical r= 0.57, Emotional Health and Mental Health r= 0.72, Emotional Health and Role Emotional r=0.48, Pain and Bodily Pain r=0.66, Fatigue and Vitality r=0.70, Planning and Social Functioning r=0.58). Most LupusQoL-US domains were able to discriminate between subjects with varied disease activity and damage. Principal component analysis revealed five factors in the US version, with physical function, pain and planning items loading on one factor.
Conclusions: These data provide evidence to support the psychometric properties of the LupusQoL-US©, suggesting its utility as an assessment tool for SLE patients in the US.