Question

Lead time bias will make it appear that the apparent survival time in the non-screened population to be _____________ than the survival time in a similar screened population.
Select one:

Select one:

a. No different

b. Greater

c. Less

d. It is impossible to compare these populations

Answer 1

answer is C) less.

Lead time bias will make it appear that the apparent survival time in the non-screened population to be less than the survival time in a similar screened population.

  The premise of screening is that it allows you to identify disease earlier, so you can initiate treatment at an early stage in order to effect cure or at least longer survival. Screening can give you a jump on the disease; this "lead-time" is a good thing, but it can bias the efficacy of screening. The two subjects to the right have the same age, same time of disease onset, the same DPCP, and the same time of death. However, if we compare survival time from the point of diagnosis, the subject whose disease was identified through screening appears to survive longer, but only because their disease was identified earlier.