Evidence quality
Lead-time bias
The appearance of longer survival because disease is detected earlier, not because death is delayed.
What it means
Definition
Lead-time bias. Lead-time bias is important in screening claims. Earlier diagnosis can increase measured survival time from diagnosis even when the actual time of death is unchanged.
What it can tell you
It can help clarify what sort of evidence or claim is being discussed.
What it cannot tell you
It cannot, by itself, prove that the headline is accurate or clinically important.
Headline trap
Why this matters in headlines
A screening test may appear to improve five-year survival without reducing mortality.