Lead time is defind is -
Lead time is the advantage gained by screening. It is the period between diagnosis by early detection and diagnosis by other means Detection programmes should concentrate on those condition where the time lag between the disease's onset and it's final critical point is sufficiently long to be suitable for population screening Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 148
Time between diagnosis and treatment
Time between point where the diagnosis is made by screening test to usual diagnosis
Time between disease onset and outcome
Time between usual time of diagnosis and outcome
Epidemiology