This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal  disorders, Subject name: Pediatrics
[{'content': 'Which of the following is diagnostic for juvenile idiopathic ahritis (JIA)? \nSelect and explain. \nA. Anti-nuclear antibody, B. ESR, C. Rheumatoid factor, D. clinical diagnosis without any diagnostic laboory tests', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Juvenile Idiopathic ahritis (JIA) is a clinical diagnosis without any diagnostic laboory tests. The meticulous clinical exclusion of other diseases and many mimicking conditions is , therefore essential. Laboratory studies, including tests for ANA and RF, are only suppoive or prognostic, and their results may be normal in patients with JIA. Ref: Nelson textbook of pediatrics 21st edition Pgno: 1263', 'role': 'assistant'}]