Objective: To determine whether serum albumin reflects disease activity in patients with systemic lupus erythematosus (SLE) with and without nephritis (LN, LNN), and whether serum albumin could be a surrogate marker of SLE disease activity overall. There is currently no clinical "gold standard" in the assessment of disease activity in SLE.

Methods: Patients with >or= 3 clinic visits within a maximum followup period of 10 years were selected from the University of Toronto Lupus Clinic database. Subjects were divided into 3 groups: LN-B, those with nephritis defined by histological findings on renal biopsies; LN-L, those with nephritis defined by laboratory abnormalities in the absence of biopsy; and LNN, those without nephritis. In a subanalysis, the renal groups were further stratified by proteinuria status. The associations of SLE-Disease Activity Index (SLEDAI-2K) with serum albumin and dsDNA were examined using the mixed model regression analysis.

Results: A total of 1078 patients were studied: 89.1% female, 71.5% white, mean age 33.6 (SD 12.6) years, and with median baseline SLEDAI-2K of 8. Serum albumin was more significantly associated with SLEDAI in LN-B and LN-L. The association was also present but weaker in the LNN group. In all LN, the associations between serum albumin and SLEDAI-2K were stronger in those with proteinuria.

Conclusions: In patients with SLE, higher SLEDAI was associated with lower serum albumin levels.