Hi Jean,
Patients diagnosed with Pseudodisease have a especially benign course of the "disease". That means at a late stage when all other true disease patients died already, they are still alive and do well. The group only consists of Pseudodisease participants now and survival would be very similar to the survival in the general population.
Lead time bias increases the survival time by moving forward
the date of diagnosis without affecting the date of death. Over time, survival in the screened group tends to run more parallel to the un-screened group because the advantage of the head start diminishes. There might be a difference between groups, but the slopes of the survival curves would be similar.
Does that help?
Kerstin