Serologically active clinically quiescent (SACQ) systemic lupus erythematosus (SLE) patients' discordance presents a clinical dilemma. Does active serology alone warrant treatment? We explore outcomes in patients with and without a prolonged SACQ period, comparing the rate of damage accrual by Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) and incidences of renal damage and coronary artery disease (CAD) over a decade.
SACQ was defined as a ≥2-year sustained period without clinical activity, with persistent serologic activity (increased anti-double-stranded DNA and/or hypocomplementemia). Antimalarials were permissible and corticosteroids/immunosuppressives were not. The SACQ patients were matched for relevant variables with SLE controls. Change in the SDI and incidences of CAD and renal damage were compared. Descriptive statistics were used; comparisons were made using t-tests and McNemar's tests.
Fifty-five SACQ patients and 110 controls were identified. The mean ± SD SDI score at 3 years from the start of the SACQ period was 0.70 ± 1.27 in the SACQ patients versus 1.13 ± 1.54 in controls (P < 0.0001), and by 10 years was 1.26 ± 1.68 versus 2.26 ± 2.23 (P = 0.001); the intergroup difference in damage significantly increased over 10 years. Initially, 2 (3.6%) of the SACQ patients had CAD versus 7 (6.4%) of the controls (P = 0.32), with 1 (1.8%) new case in SACQ patients versus 8 (7.3%) new cases in controls over 10 years (P = 0.06). Baseline serum creatinine level did not differ between the groups. By definition, the SACQ patients had no baseline proteinuria versus 13 (12.3%) of the controls (P < 0.0001). By year 10, 2 (3.6%) SACQ patients versus 26 (23.6%) controls had renal damage (P < 0.0001).
Patients with a prolonged SACQ period accrued less damage over a decade compared to matched controls, supporting management with active surveillance without treatment during an SACQ period.