This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune system, Subject name: Medicine
[{'content': 'RA is best diagnosed by? \nSelect and explain. \nA. IgA RF\\/, B. IgG RF\\/, C. IgM RF\\/, D. Anti CCP antibody', 'role': 'user'}, {'content': 'Answer: D \nExplanation: to establish diagnosis of rheumatoid ahritis are * Clinical criteria * ESR and CRP * Ultrasound or MRI * Rheumatoid factor and anti-citrullinated peptide antibodies DAVIDSON&;S 22nd EDITION;PAGE NO 1100', 'role': 'assistant'}]