Review Question - QID 214678

A 27-year-old otherwise healthy woman presents to the clinic with complaints of joint pain for the past week. The patient reports acute onset pain in her metacarpal and proximal interphalangeal joints, wrists, and knees bilaterally. She endorses stiffness in the joints that is the most noticeable in the morning and improves throughout the day. She denies any weakness, paresthesia, ulcers, or photosensitivity. The patient currently works as a kindergarten teacher and denies any other medical history. She reports a cold about 2 weeks ago that has since resolved. A physical examination demonstrates some tenderness to palpation at the joints mentioned and skin findings shown in Figure A. What laboratory abnormality is the most specific for this patient’s disease?