How can we define low disease activity in systemic lupus erythematosus?

BACKGROUND: In recent years, low disease activity emerged as a state that is associated with improved long-term outcomes in systemic lupus erythematosus (SLE). Our aim was to review the current concepts for low disease activity in SLE in order to serve as the basis of a future consensus for standardization. METHODS: The PubMed database was searched for relevant articles from inception up to July 2018. Medical Subject Headings (MeSH terms) included "lupus" AND "low disease activity" OR "minimal disease activity". RESULTS: Three different definitions of low disease activity in lupus have been proposed. Minimal disease activity (MDA) is defined as a clinical SLE Disease Activity Index 2000 (SLEDAI-2K)≤1 on antimalarials, immunosuppressives in standard doses and prednisone ≤5 mg/day. Low disease activity (LDA) allows for a clinical SLEDAI-2K≤2 maintained on antimalarials only. Lupus Low Disease Activity State (LLDAS) accepts a SLEDAI-2K≤4 with no activity from major organ systems, a Physician's Global Assessment of ≤1 with no new activity, prednisone dose ≤7.5 mg/day and standard doses of antimalarials, immunosuppressives and biologics. Active serology (anti-dsDNA and complement C3/C4) is not included in the MDA and LDA but counts towards disease activity in the LLDAS definition. All definitions were associated with less damage-accrual and mortality in the long-term that were comparable to those of clinical remission. CONCLUSIONS: There is solid evidence that low disease activity is associated with improved outcomes in SLE and could serve as a therapeutic target in daily practice and clinical trials. Future research should focus on advancing a consensus for the best possible definition.