A 22-year-old female presents with a 6-week history of pain and swelling in her wrists and the small joints of her hands. She reports stiffness in the morning that lasts for over an hour. On examination, there is symmetrical swelling and tenderness of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. What is the most specific blood test to support the suspected diagnosis?