This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Screening, Subject name: Social & Preventive Medicine
The usefulness of a screening test in a community depends on its- 
Select and explain. 
A. Sensitivity, B. Specificity, C. Reliability, D. Predictive value
A: Sensitivity
Answer: A: Sensitivity 
Explanation: Ref:Parks 23rd edition pg 139 An ideal screening test should have 100% sensitivity. Sensitivity is defined as the ability of a test to identify correctly all those who have the disease, that is "true positive"