Figures are from-- and longer (but not necessarily clearer) explanations can be found here: http://ecp.acponline.org/marapr99/primer.htm
Lead-time bias: Overestimation of survival duration due to earlier detection by screening than clinical presentation.
Length-time bias: Overestimation of survival duration due to the relative excess of cases detected that are slowly progressing.
- Imagine all 12 cases below are the same disease. Instead of being seen as rapidly progressive 50% of the time, rapidly progressive disease is only detected in 33% of positive screens.
KEY MNEMONIC:
Length-time bias is due to slow cases being detected more often simply because they are slowly progressing. Remember the "g" in length is for slowly progressing.
Lead-time bias is due to early detection. Remember the "d" in lead is for early detection.
Content on this page has not been checked for accuracy. The author's credentials have not been confirmed. Always use multiple peer-reviewed scholarly sources and good clinical judgement in your decision making.
Create an account for FREE to remove ads and access features including browsing history, favorites and private notes.