TNFRSF11B and systemic lupus erythematosus: After multivariate analysis age (β = -0.326, 95% CI -0.055 to -0.015; P = 0.001) and levels of anti-Sm antibodies (β = 0.229, 95% CI 0.006 to 0.053; P = 0.016) were independently associated with sRANKL/OPG ratio levels in SLE patients.