Soru

A $41$-year-old woman comes to the primary care clinic for evaluation of joint pain and stiffness that began gradually over the past $3$ months. She reports that the pain primarily affects her wrists and fingers on both hands. The stiffness is most pronounced upon awakening and typically takes about $2$ hours to improve. She feels generally fatigued but denies fevers, weight loss, or skin rashes. Her vital signs are within normal limits. Physical examination demonstrates boggy swelling, warmth, and tenderness of the second and third metacarpophalangeal and proximal interphalangeal joints bilaterally. There is no erythema or joint deformity. A routine complete blood count obtained last week for a wellness visit showed a hemoglobin level of $11.2 \text{ g/dL}$ and a mean corpuscular volume of $88 \text{ fL}$. Which of the following is the most appropriate next step in the diagnostic workup?