Background/Purpose: Anti-DNA antibodies and serum complement levels are considered important biomarkers for disease activity in SLE.  Despite this many SLE patients present serologically active (positive antibody and or low complement) but clinically quiescent (SACQ). We aim to determine the frequency of SACQ in a multicentre, multinational cohort.

Methods: An inception cohort of SLE patients from 31 centres in 12 countries has been assembled according to a standardized protocol between 2000 and 2013 to study the risk factors for atherosclerosis. Patients enter the cohort within 15 months of SLE diagnosis (≥4 ACR criteria). Clinical and laboratory features of SLE and comorbidities are gathered in a standardized protocol at yearly intervals. SACQ was defined as at least two consecutive yearly visits with SLEDAI of 2 or 4 from serologic activity only (increased anti-double-stranded DNA and/or hypocomplementemia), during which patients could be taking antimalarials, but not steroids or immunosuppressives. We examined patients 1 year after the SACQ period and beyond. Flare was defined as any increase in clinical activity. Since patients were mandated to only be on antimalarials it is unlikely they had moderate to severe flares between yearly assessment visits. Serologically quiescent and clinically quiescent (SQCQ) was defined as SLEDAI-2K score of 0.

Results: 91 of 1837 (5%) patients met the criteria for SACQ.  Of the 91 patients studied, 86.8% were female and the race/ethnicity distribution was 65.9% Caucasian, 9.9% Black, 13.2% Asian, 7.7% Hispanic and 3.3% other. The age at SLE diagnosis was 34.6 ± 11.9 years.  Disease duration at last follow–up was 7.1± 3.0 years. Fifty-five patients did not retain SACQ status after the first year and 36 patients experienced a prolonged SACQ. Of the 55 patients that did not retain SACQ status, 25 (45.45%) flared, 14 (25.45%) became SQCQ and 16 (29.09%) were censored at the last visit.  Of the 36 patients that went onto prolonged SACQ: 9 (25.00%) patients flared after 3 years of SACQ, 4 (11.11%) patients became SQCQ and 23 (63.89%) patients were censored at their last visit.

Conclusion:  Sixty percent of the SACQ patients no longer retained SACQ status in the first year, while 40% experienced a prolonged SACQ period and 25% of those flared later. Therefore treatment decisions in these patients must be based on close clinical observation.