SLE-DAS enables an accurate definition of severe lupus disease activity: derivation and validation in a post hoc study of anifrolumab phase II and III studies.

OBJECTIVES

This study aimed to derive and validate a cut-off for severe disease activity (SDA) using the SLE Disease Activity Score (SLE-DAS) and compare its accuracy and impact on health-related quality of life (HR-QoL) with the British Isles Lupus Assessment Group 2004 (BILAG-2004) and SLE Disease Activity Index 2000 (SLEDAI-2K).

METHODS

We performed a post hoc analysis of pooled placebo arm data from the MUSE (A Phase II, Randomized Study to Evaluate the Efficacy and Safety of MEDI-546 in Subjects with Systemic Lupus Erythematosus), TULIP-1 and TULIP-2 (Treatment of Uncontrolled Lupus via the Interferon Pathway) trials, including 438 patients with moderate-to-severe SLE. SLE-DAS was scored retrospectively, and a cut-off for SDA was derived using receiver operating characteristic (ROC) curves against the BILAG-2004 numerical score >11 as gold standard. Multiple linear regression analysis and Cohen's d effect size were applied to evaluate the effectiveness of SLE-DAS, BILAG-2004 and SLEDAI-2K SDA classifications in capturing HR-QoL patient-reported outcomes (PROs).

RESULTS

The optimal SLE-DAS cut-off for SDA was >9.90 (area under the ROC curve=0.847, sensitivity=77.8%, specificity=79.6%). Patients classified as SDA by both SLE-DAS and BILAG-2004 or only by SLE-DAS exhibited similar disease activity, while those classified by BILAG-2004 alone had less severe disease and better HR-QoL. The SLE-DAS cut-off was associated with worse HR-QoL across multiple PROs more consistently than BILAG-2004 or SLEDAI-2K.

CONCLUSION

The SLE-DAS cut-off for SDA provides an accurate definition of SDA in SLE, with good discriminative power and consistent associations with worse HR-QoL. This SLE-DAS definition enhances disease activity classification and offers a practical tool for guiding treatment decisions in clinical practice, as well as selecting patients with SDA for inclusion in clinical trials.