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: Medicine
[{'content': 'Skin testing with tuberculin-PPD is most widely used in screening for: \nSelect and explain. \nA. Active TB, B. Latent M. tuberculosis infection, C. Miliary TB, D. Overwhelming TB', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Skin testing with tuberculin is used in screening for latent M. tuberculosis infection (LTBI). The test is of limited value in active TB. False-negative reactions are common in immunosuppressed patients and in overwhelming TB. False-positive reactions may be caused by infections with nontuberculous mycobacteria and BCG vaccination. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 1351', 'role': 'assistant'}]