Comparison of the responsiveness of lupus disease activity measures to changes in systemic lupus erythematosus activity relevant to patients and physicians

Abstract

Both the revised Systemic Lupus Activity Measure (SLAM-R) and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) are valid and reliable measures of disease activity in systemic lupus erythematosus (SLE). However, more study of their responsiveness is needed. The purpose of this study was to compare the responsiveness of SLAM-R and SLEDAI to disease activity changes relevant to physicians and patients. Patients were evaluated monthly for up to 12 months. At each visit, the physician completed SLAM-R and SLEDAI. Patients and physicians assessed whether relevant improvement or worsening of disease activity had occurred since the previous visit. Based on repeated measurements, effect size (ES), standardized response mean (SRM), and control-standardized response mean (CSRM) were calculated for each response category, with bootstrap-based 95% confidence intervals (CIs). Seventy-six patients contributed 471 score changes. For physicians' responses, the CSRMs for SLAM-R and SLEDAI were -0.47 versus -0.42 for improvement, 0.04 versus 0.003 for no change, and 0.65 versus 0.66 for deterioration. For patients, the CSRMs for SLAM-R and SLEDAI were -0.31 versus -0.18 for improvement, -0.08 versus 0.06 for no change, and 0.48 versus 0.05 for deterioration. Only for SLAM-R did the 95% CIs exclude zero when improvement or deterioration were detected. Similar results were found for ES and SRM. Both SLAM-R and SLEDAI are responsive to changes in SLE disease activity important to physicians. Only SLAM-R is responsive to changes important to patients. These differences may result from the inclusion of subjective SLE manifestations in SLAM-R.