Background A gold-standard definition of severe SLE disease activity is lacking for use both in clinical trials and daily clinical setting. The SLE-DAS is an easy to use, validated instrument, with high accuracy and sensitivity to change in SLE disease activity. The SLE-DAS definition for severe disease activity (SDA) was recently derived and validated.

Objectives To compare the disease features and health-related quality of life (HR-QoL) of patients fulfilling the SDA definition both by SLE-DAS and BILAG-2004 with those in SDA: (a) only by SLE-DAS (but not BILAG-2004); (b) only by BILAG-2004 (but not SLE-DAS).

Methods Post-hoc analysis of the aggregated intention-to-treat, placebo arm participants, in the anifrolumab versus placebo for moderate-to-severe SLE phase 2 and 3 RCTs [MUSE (NCT01438489), TULIP-1 (NCT02446912), TULIP-2 (NCT02446899)]. At the RCTs week 12, we analyzed the physicians’ assessments (including clinical and analytical data, BILAG-2004, CLASI-A, SLEDAI-2K), and patient reported outcomes (PROs) [LupusQoL, EQ-5D, FACIT-F, Patient Global Assessment (PtGA) scores]. The SLE-DAS was retrospectively scored. Active lupus features and PROs at week 12 were compared between the group of patients classified in SDA by both the SLE-DAS (>9.90) and BILAG-2004 (>11) vs patients classified in SDA only according to SLE-DAS or BILAG-2004. Chi-squared, Fishers’ or Mann-Whitney tests were applied.

Results From 438 SLE patients, at week 12 were classified in SDA: 34% by both instruments (SLE-DAS+BILAG-2004), 12.6% by SLE-DAS only, and 10.05% by BILAG-2004 only. The groups in SDA according to SLE-DAS+BILAG-2004 and to SLE-DAS-only did not present any significant differences in active disease features and the HR-QoL PROs (table 1). In contrast, patients classified in SDA only by BILAG-2004 presented significantly lower SLEDAI-2K, less serositis, nephritis and arthritis. Notably, patients in SDA by BILAG-2004 alone presented significantly less severe impact in the HR-QoL PROs (table 1).

Conclusion Patients in SDA defined either by SLE-DAS+BILAG-2004 or by SLE-DAS only present similarly severe disease, both according to active lupus features and the HR-QoL PROs. Contrarily, those classified in SDA only by BILAG-2004 may present less severe disease, according both to the physician and patient assessments.

Acknowledgement This publication is based on research using data from data contributors AstraZeneca that has been made available through Vivli, Inc. Vivli has not contributed to or approved, and is not in any way responsible for, the contents of this publication.