A novel lupus activity index accounting for glucocorticoids: SLEDAI-2K glucocorticoid index

Abstract

To develop and validate a modification of SLEDAI-2K to accurately describe disease activity while accounting for glucocorticoid (GC) doses. The first two phases focused on the development of the index. Phase 1: identification of scenarios of real patients seen prospectively in a longitudinal cohort. Phase 2: derivation of an equation that explains the association between SLEDAI-2K and GC doses using physician global assessment as the external construct. Phase 3: comparison of SLEDAI-2K and SLEDAI-2K GC (SLEDAI-2KG), using different cut-off points (4-7), in identifying responders in response to therapy. In phase 1, 150 scenarios with different organ involvement and a range of GC doses were identified. In phase 2, three rheumatologists ranked disease activity using physician global assessment. A quadratic linear regression model relating GC doses and SLEDAI-2K resulted in the following equation: SLEDAI-2KG score = SLEDAI-2K score + [0.32 × GC - 0.0031 × GC2]. The weighted score of different GC doses was derived. In phase 3, SLEDAI-2KG identified more responders in a total of 111 patients at 6 months (84 vs 93%) and at 12 months (76 vs 92%) compared with SLEDAI-2K. SLEDAI-2KG performances were superior to SLEDAI-2K with all cut-off points (5-7). We developed a modification of SLEDAI-2K, SLEDAI-2KG, that describes disease activity while accounting for GC dose category. SLEDAI-2KG identifies more responders compared with SLEDAI-2K.