This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
In a case of undifferentiated arthritis, presence of anti-cyclic citrullinated peptide (anti CCP) indicates strong possibility of which of the following? 
Select and explain. 
A. Rheumatoid arthritis, B. Systemic lupus erythematosis, C. Mixed connective tissue disorder, D. Reactive arthritis
A: Rheumatoid arthritis
Answer: A: Rheumatoid arthritis 
Explanation: Anticitrullinated peptide antibody test (Anti ccp) test is more specific than rheumatoid factor for diagnosis of rheumatoid arthritis. It may be positive very early in the course of the disease.