lead time bias
A systematic error in screening studies where earlier detection appears to improve survival without actually affecting disease outcome.
Full Definition
Lead time bias is a form of bias that occurs in cancer screening studies when early detection through screening appears to prolong survival time, but the apparent benefit is due to earlier diagnosis rather than actual improvement in prognosis. The 'lead time' is the interval between when a cancer is detected by screening and when it would have been detected clinically due to symptoms. This bias can make screening programs appear more effective than they actually are, as patients seem to live longer after diagnosis even though their overall lifespan remains unchanged.
Usage
Usage note: Hyphenate as 'lead-time bias' when used as a compound modifier. Often confused with length-time bias, which is a related but distinct concept.
In Context
- "Researchers must account for lead time bias when evaluating the mortality benefits of new screening programs." — Epidemiology study
- "The apparent survival improvement may be due to lead time bias rather than genuine therapeutic benefit." — Research methodology paper