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': "The usefulness of a 'screening test' in a community depends on its - \nSelect and explain. \nA. Sensitivity, B. Specificity, C. Reliability, D. Predictive value", 'role': 'user'}, {'content': "Answer: A \nExplanation: Screening refer to 'the search for unrecognized disease or defect by means of rapidly applied tests, examinations or other procedures in apparently healthy individuals'\nFor screening a disease the most important parameter is sensitivity\n\nSensitivity is defined as the ability of a test to identify correctly all those who have the disease i.e., true positives as it reflects the ability to detect those who have the disease amongst the hidden cases in the community.\n\nFor confirming a patient as diseased most important parameter is specificity\n\nSpecificity is defined as the ability of a test to identify correctly all these who do not have the disease i.e., true negative.\n\nMemo: ELISA is a sensitive test for HIV: ELISA is used as screening test for HIV\nWestern blot is a specific test for HIV : Western blot is used as a confirmatory test for HIV.\n\nUsefulness of a screening test is given by sensitivity\nStatistical index of diagnostic accuracy → specificity", 'role': 'assistant'}]