In lupus, serial evaluation of dsDNA antibody titers and complement (C3 and C4) in blood samples have been useful in assessing disease activity in patients. High levels of C3a, a split product of C3, are particularly sensitive and reflective of lupus flares. Our study looks at whether elevations in C3a can predict lupus flares and how C3a compares with other conventional blood indicators such as dsDNA antibody, C3, C4, and CH50. The utility of serial anti-dsDNA antibodies and complement measurements in clinical decision-making for people with systemic lupus erythematosus (SLE) remains controversial. This study has two specific parts designed to address these issues.