Approach to joint pain and swelling Quiz: Ace Your Exams

A 52-year-old woman presents to the primary care office due to 6 weeks of joint pain in both hands. She has joint stiffness lasting 1 hour in the mornings and the pain and stiffness worsens with prolonged inactivity. The patient has also recently developed fatigue and malaise, but she has no fever or weight loss. She has no past medical history and does not take any medication. She does not use tobacco, alcohol, or recreational substances and is not currently sexually active. She works as a high school principal. Vital signs are unremarkable. On physical examination, multiple proximal interphalangeal joints and metacarpophalangeal joints of both hands are edematous and tender to palpation. She has pain when she moves them and her grip is weak, secondary to pain. Initial complete blood work and basic metabolic panel are normal. Which of the following is most likely to be positive and confirm the underlying diagnosis?