Background Identification of patients at risk of developing renal flares is imperative to optimise management in systemic lupus erythematosus (SLE). We aimed to identify predictors of renal flares in patients receiving treatment for active extra-renal SLE.
Methods Data from BLISS-52 (NCT00424476), BLISS-76 (NCT00410384), BLISS Northeast Asia (NCT01345253), and BLISS-SC (NCT01484496) were used. The trials included patients with active, seropositive SLE and excluded active severe renal SLE. Participants were assigned to belimumab or placebo, on top of non-biologic standard therapy. We investigated baseline levels of traditional biomarkers in blood and urine as potential predictors of renal flares during a 52–76-week follow-up. We used adjusted Cox regression models to estimate hazards of renal flares.
Results Out of 3225 participants, 192 developed a renal flare after a median follow-up time of 197 days. Baseline serum albumin (HR 0.9; 95% CI: 0.9–0.9), proteinuria (HR: 1.3; 95% CI: 1.2–1.4), and low C3 levels (HR: 1.8; 95% CI: 1.3–2.5) were robust determinants of renal flares in the pooled study population, as well as in the belimumab and placebo subgroups. Furthermore, we observed an association between anti-dsDNA positivity and renal flares in univariable models, which attenuated in multivariable models (figure 1). Anti-Sm antibody positivity was associated with renal flares in the placebo, but not in the belimumab subgroup, whereas anti-ribosomal P antibodies were associated with renal flares in the belimumab subgroup only. Anti-cardiolipin antibody positivity (any isotype) predicted renal flares in the belimumab subgroup, but yielded a negative association in the placebo subgroup.
Conclusions High baseline proteinuria levels, hypoalbuminaemia, and C3 consumption were robust determinants of imminent renal flares. Beyond anti-dsDNA, anti-ribosomal P and aCL antibody positivity may prove valuable early signals of imminent renal flares in belimumab-treated patients, whereas anti-Sm antibody positivity may predict renal flares in patients treated with non-biological standard therapy.
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