HSS 3332 Lecture Notes - Lecture 3: Genetic Counseling, Overdiagnosis, Thyroid Cancer
9 Nov 2017
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Primer on lead time, length and overdiagnosis bias and prostate cancer: screening and. Give an example of each type of bias: lead time bias. Overestimation of survival duration among screen-detected cases (relative to those detected by signs and symptoms) when survival is measured from diagnosis. In the figure below (representing one patient) there is a 10 year survival at the point of the clinical diagnosis (old), but a 15 year survival from the early diagnosis (new). This is simply a reflection of earlier diagnosis, however, as the overall survival time of the patient is unchanged: length bias. Overestimation of survival duration among screen-detected cases due to the relative excess of slowly progressing cases. These are disproportionally identified by screening because the probability of detection is directly proportional to the length of time during which they are detectable (thus inversely proportional to the rate of progression).
