Background/Purpose:   It is challenging to describe disease activity in SLE in the context of multiple levels of glucocorticoids (GC) treatment. We aim to develop and validate a new index, SLEDAI-2K Glucocorticoids Index (SGI), to accurately describe disease activity while accounting for GC doses.

Methods:   The first 2 phases focused on to the development of the index. Phase 1: identification of scenarios of real patients seen prospectively in a longitudinal cohort at the centre in the last 20 years. Phase 2: derivation of an equation that explains the association between SLEDAI-2K and GC dose while using physician global assessment (Likert scale [LS] 0-7) as the gold standard. Phase 3 was to validate the new index, SGI, against SLEDAI-2K in a cohort of active patients on standard of care treatment. Phase 1 Scenarios were identified using 2 data sampling approaches. First, the top 13 most common organ involvement combinations were identified. From each of these combinations, random scenarios with a wide spectrum of GC doses were selected. Second, patients in the entire database were grouped into 7 categories based on the GC dose [5, 10, 15, 20, 30, 50 and 60 mg/day] and 10 patients were selected randomly from each category. Scenarios included information on patients’ SLEDAI-2K score, organ involvement combination and GC dose.   Phase 2 3 rheumatologists ranked disease activity with LS. The sample size calculation was on the assumption of reliability with ICC ≥0.80 and required a minimum of 46 scenarios.   Phase 3 An independent cohort was used for the validation. We hypothesized that in patients with improvement and worsening (SLEDAI-2K decrease ≥4 and increase >4 respectively), the change in SLEDAI-2K and SGI scores will move in the same direction.

Results:   1-The first approach yielded 29577 visits in 1400 patients and 51 scenarios. The second approach yielded 18178 visits in 1086 patients and 80 scenarios. 2- 131 scenarios were summarized and ranked by 3 rheumatologists leading to 393 records. A perfect agreement in LS was achieved; ICC (2, k) of 0.89 (95% CI: 0.83, 0.89). A quadratic linear regression model relating GC and SLEDAI-2K was structured in this equation: SGI score =SLEDAI-2K score + [3.65 + 0.29 * GC – 0.0027 (GC * GC)]. The weight score of GC doses was derived and represented in table 1. For instance, SLEDAI-2K of 6 on 10 mg of GC provides SGI of 9. The application of SGI is illustrated in table 1. 3- Concurrent Construct Validity: Of the 158 patients studied, 109 patients improved, 38 remained unchanged, and 11 worsened at 9-12 months follow up. At follow up SLEDAI-2K and SGI correlated highly (r= 0.87) and changed in the same direction in patients with improvement and worsening proving the validity of SGI.

Conclusion:   We developed and validated a novel lupus disease activity index, SGI, that describes disease activity while accounting for GC dose.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/development-and-initial-validation-of-a-novel-lupus-disease-activity-index-to-account-for-glucocorticoids-sledai-2k-glucocorticoids-index-sgi/