30th April 2024

A 58-year-old woman presents with a six-month history of symmetrical joint pain and stiffness in her hands, particularly in the mornings.

A 58-year-old woman presents with a six-month history of symmetrical joint pain and stiffness in her hands, particularly in the mornings. The stiffness lasts for more than an hour. She also reports feeling generally unwell and has experienced unintentional weight loss. On examination, there is swelling and tenderness in her wrist and finger joints, with visible erythema. She has no previous history of joint problems or any family history of autoimmune diseases.

Investigations:

Erythrocyte sedimentation rate (ESR): 40 mm/hr (0–20)

C-reactive protein (CRP): 12 mg/L (<5)

Full blood count: Normal

Which investigation is most appropriate to confirm the diagnosis of rheumatoid arthritis?