A 35-year-old woman presents with symmetrical polyarthritis affecting her metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints, morning stiffness lasting over an hour, and fatigue for the past 6 months. Physical exam reveals swollen and tender MCP and PIP joints bilaterally. Which of the following laboratory findings would most strongly support a diagnosis of rheumatoid arthritis?
✓ Correct Answer: Option C
Positive anti-cyclic citrullinated peptide (anti-CCP) antibody is highly specific for rheumatoid arthritis and can be detected early in the disease course, making it a strong diagnostic marker.