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lead-time bias

— An apparent increase in survival due to detecting a health condition such as cancer at an early stage, when there is no actual effect on survival, just a longer period with the diagnosis.

Full explanation:

Lead-time bias occurs when follow-up of participants in treatment comparison groups begins at different times.

Example:

For example, even if treatments for people with cancer are not effective, people whose cancer is detected early by screening will appear to survive longer than people without screening, whose cancer is not detected until they have symptoms.

See also:

bias  ·  length-time bias  ·  screening

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