In the first, we will take advantage of a unique opportunity to collaborate with a large, multicenter NIH-sponsored protocol, the Safety of Estrogens in Systemic Lupus National Assessment (SELENA) trial. We will perform an observational study of approximately 1,000 women enrolled in the SELENA trial to assess the sensitivity, specificity, and predictive value of anti-dsDNA antibodies, C3, C4, CH50, and C3a desArg. Using samples from patients enrolled in the SELENA study, we will perform subgroup analyses in diverse ethnic groups, patients treated with exogenous estrogen, and patients with chronically depressed CH50.