This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rheumatoid Ahritis, Subject name: Medicine
The most specific antibody for Rheumatoid ahritis is? 
Select and explain. 
A. Antinuclear antibody (ANA), B. Rheumatoid factor, C. Anti-cyclic citrullinated peptide (anti-CCP) antibody, D. Anti-double stranded DNA antibody
C: Anti-cyclic citrullinated peptide (anti-CCP) antibody
Answer: C: Anti-cyclic citrullinated peptide (anti-CCP) antibody 
Explanation: Anti-CCP is the most specific antibody for rheumatoid ahritis with specificity of 95%. 20% patients have elevated ANA and ESR. CRP levels are elevated propoional to disease activity.