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. Author manuscript; available in PMC: 2014 Nov 1.
Published in final edited form as: Ann Epidemiol. 2013 Aug 27;23(11):10.1016/j.annepidem.2013.07.021. doi: 10.1016/j.annepidem.2013.07.021

Figure 1.

Figure 1

Theoretical representation of the progression of disease for a subject in the a) absence and b) presence of screening. This diagram demonstrates for the screen-detected case that the date of diagnosis is advanced (from tC to tS) and survival time is extended (from [tC, tD] to [tS, tD]) both by the length of the lead-time interval. Notice that once a screen-detectable tumor develops (t0), over time the disease passes through a preclinical phase (either [t0, tS] or [t0, tC]), a diagnosis (either at tS to tC), a survival period, and eventually leads to death (tD). (With permission from 2, copyright 1999. Elsevier Science Inc. All rights reserved.)