A 24-year-old African American woman with a 3-year history of systemic lupus erythematosus (SLE) presents to the clinic with increased fatigue, low-grade fevers, and a flare of her malar rash. Over the past week, she has noted swelling in her lower extremities. Laboratory studies reveal proteinuria of 1.2 g/day and red blood cell casts on urinalysis. Complement levels (C3, C4) are decreased. Which autoantibody titer is most likely to correlate with her current disease activity and renal involvement?