The development and validation of a disease-specific instrument to measure quality of life in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease. In the evaluation of patients with SLE it is important to measure not only disease activity and damage but also the impact of the disease on their health related quality of life (HRQoL). Disease-specific HRQoL measures are considered to be more relevant and sensitive to change. As none were currently available, this present work was conducted to develop and validate a patient-derived measure, the Lupus Quality of Life (LupusQoL) Questionnaire and to use it to describe HRQoL in a group of patients. Several stages of development led to the validation of the questionnaire. The generation of items was informed by: existing HRQoL literature; other FIRQoL measures; consultation with the rheumatology multi-disciplinary team; and patient interviews (n=30). From this, a measure comprising 67 items was generated. Twenty patients completed this initial version providing critical feedback regarding face validity and structure, content of the items and response scales, leading to further revision of the LupusQoL. This revised version of the LupusQoL (63 items) was completed by 322 patients. Principal components analysis and Cronbach alpha coefficients highlighted eight domains. The LupusQoL was further revised (42 items) based on factor analysis, clinical decision and patient feedback. Principal components analysis was performed on the data from the second version of the LupusQoL, completed by 213 patients. This confirmed the factor structure of the LupusQoL. The final measure contains 34 items comprising eight domains: physical functioning, pain, emotional functioning, fatigue, body image, intimate relationships, planning and burden to others. Cronbach alpha coefficients (all values > 0.8) and item to domain correlations showed good internal consistency of the subscales. Test-retest reliability and concurrent validity have also shown that the instrument is robust. For all domains except fatigue those with no current activity and/or only mild activity in any systems reported a better HRQoL than (a) those with moderate activity in any systems and (b) those with severe active disease in any systems (p'c0.05). Patients with no damage reported a better HRQoL than those with damage for physical health, pain, planning, intimate relationships and burden to others (p