OBJECTIVE: Some patients with systemic lupus erythematosus (SLE) are clinically quiescent despite persistent serologic activity. We determined the frequency of serologically active clinically quiescent (SACQ) SLE and its outcomes in prospectively followed patients with SLE. METHODS: Patients with SLE followed between July 1970 and April 2008 with visits < or = 18 months apart were identified. SACQ was defined as a > or = 2-year sustained period without clinical activity with persistent serologic activity (increased anti-dsDNA and/or hypocomplementemia), during which antimalarials but neither steroids nor immunosuppressives were permissible. Characteristics of patients with an SACQ period and its features were analyzed. To determine flare predictors, anti-dsDNA and complement levels in SACQ patients who experienced flare were compared to levels in those who did not. Descriptive statistics were used; comparisons were made using t tests and chi-squared tests. RESULTS: Of the patients studied, 56/924 (6.1%) were SACQ. They differed significantly from the non-SACQ SLE population only in the presenting SLE Disease Activity Index 2000 (7.34 vs 10.1 in non-SACQ), and frequency of steroid use (33.9% vs 60.8% in non-SACQ) and immunosuppressive use (3.6% vs 19.4% in non-SACQ) at first visit. Median SACQ period was 158 weeks. Thirty-three (58.9%) patients who were SACQ experienced flare (at median 155 weeks), 6 (10.7%) became clinically and serologically quiescent (236 weeks), and 17 continued to be SACQ (159 weeks). Common flare manifestations were arthritis, mucous membrane involvement, and sterile pyuria. Fluctuations in anti-dsDNA or complement levels did not predict flare. CONCLUSION: Fifty-nine percent of SACQ patients experienced flare, but after a median of 3 years. Fluctuations in complement and anti-dsDNA levels did not predict flare, thus treatment decisions in these patients must rely upon close clinical observation. Alternative predictive biomarkers warrant study.
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