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: Social & Preventive Medicine
[{'content': 'K 39 antigen is used in diagnosis of: \nSelect and explain. \nA. Malaria, B. Typhus fever, C. Kala azar, D. Enteric fever', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Rapid Diagnostic Test: Now a rapid dipstick test based on the recombinant K39 protein is available for rapid diagnosis of kala-azar. K39 is an epitope apparently conserved on amastigotes of Leishmania species that cause visceral infection; by use of laboratory ELISA testing, circulating anti-K39, IgG is detectable in 95%- 100% of patients who have kala-azar, irrespective of geographic region. Ref:', 'role': 'assistant'}]