To assess the reliability, 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 longitudinal cohort of SLE patients predominantly derived from the Georgia Lupus Registry, a population-based registry established in Atlanta, Georgia, United States (US). Seven hundred eleven participants with documented SLE completed the SA-BILD. To test reliability, the SA-BILD was re-administered to 32 patients. Criterion validity was examined in 150 respondents for whom the SLICC/ACR Damage Index (SDI) was also completed. Construct validity was assessed among 711 GOAL participants 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 over 80% for most SA-BILD items. The Spearman rank correlation for SDI and SA-BILD was moderately high (r=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 is reliable and has very good or good criterion validity compared to the SDI when tested in a predominantly African American cohort of US SLE patients. Associations of SA-BILD scores with sociodemographics and health status are consistent with previous studies. These findings support the use of SA-BILD as a valid measure of patient-reported damage in SLE.