A 35-year-old female presents with bilateral symmetric polyarthritis involving the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints, with morning stiffness lasting 90 minutes. Which autoantibody exhibits the highest diagnostic specificity for this condition?

Answer and explanation

Correct answer: B. Anti-cyclic citrullinated peptide (anti-CCP)

  1. Step 1: The clinical presentation is classic for rheumatoid arthritis (RA).
  2. Step 2: Anti-cyclic citrullinated peptide (anti-CCP) antibodies possess high diagnostic specificity (> 95-98%) for rheumatoid arthritis, significantly superior to rheumatoid factor (RF), and can be detected early in the disease course.
Answer
Anti-cyclic citrullinated peptide (anti-CCP).
Why not the others: 'Antinuclear antibody (ANA)' is sensitive for systemic lupus erythematosus (SLE) but non-specific; 'Rheumatoid factor (RF)' is sensitive but seen in Sjögren syndrome, hepatitis C, and endocarditis; 'Anti-double stranded DNA (anti-dsDNA)' is highly specific for SLE.

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