This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Definition and Concepts, Examples from NHPs, Subject name: Social & Preventive Medicine
'Lead time' refers to the time between: 
Select and explain. 
A. Disease onset and first critical diagnosis, B. Disease onset and first possible point of detection, C. First possible point of detection and final critical point, D. First possible point of detection and usual time of diagnosis
D: First possible point of detection and usual time of diagnosis
Answer: D: First possible point of detection and usual time of diagnosis 
Explanation: Lead Time Lead time is the advantage gained by screening (leading the time of diagnosis). It is time between First possible point of detection and usual time of diagnosis.