To assess the reliability and criterion and construct validity of the self-administered Brief Index of Lupus Damage (SA-BILD), a patient-reported measure of organ damage in systemic lupus erythematosus (SLE).
The validity of the SA-BILD was assessed using data from the Georgians Organized Against Lupus (GOAL) survey. GOAL is a longitudinal cohort of SLE patients predominantly derived from the Georgia Lupus Registry, a population-based registry established in Atlanta, Georgia. In total, 711 participants with documented SLE completed the SA-BILD. To test reliability, the SA-BILD was readministered to 32 patients. Criterion validity was examined in 150 respondents for whom the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) was also completed. Construct validity was assessed among 711 GOAL participants by dividing the SA-BILD scores into quartiles and examining the association with demographics, health status, and health care utilization.
The test-retest correlation score was 0.93 (P < 0.0001), the item-by-item agreement with the SDI was >80% for most SA-BILD items, and the Spearman's rho correlation coefficient for the SDI and SA-BILD was moderately high (ρ = 0.59, P < 0.0001). SA-BILD scores showed significant associations in the expected directions with age, disease duration, disease activity, overall health, comorbidity index, and physician visits.
The SA-BILD was reliable and had very good or good criterion validity compared with the SDI when tested in a predominantly African American cohort of US SLE patients. Associations of SA-BILD scores with sociodemographics and health status were consistent with previous studies. These findings support the use of the SA-BILD as a valid measure of patient-reported damage in SLE.