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': 'Sentinel surveillance is used to detect: March 2009, March 2013 (e) \nSelect and explain. \nA. New cases, B. Missed cases, C. Old cases, D. Reference cases', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: Missed cases The main objectives of surveillance are: To provide information about new and changing trends in the health status of population To provide feedback which may be expected to modify the policy Provide timely warning of the public health disasters so that timely interventions can be mobilized. Sentinel surveillance is a method for identifying all the missing cases and thereby supplementing the notified cases.', 'role': 'assistant'}]