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: Surgery
[{'content': 'All of the following are true regarding ankylosing spondylitis except: March 2010 \nSelect and explain. \nA. Involvement of sacroiliac joint, B. Most of people are HLAB27 positive, C. 50% of patients may have urinary infection, D. Bamboo spine may be a radiological feature', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: 50% of patients may have urinary infection', 'role': 'assistant'}]