See also:

• Lead-time bias versus Length-time bias

 

Questions (Scroll down for answers)

1. New guidelines in one jurisdiction advised colon cancer screening start at age 45 rather than 50. In follow-up studies, the overall mortality rate for colon cancer (deaths per 100,000 per year) decreased. This is an example of:

 

A) Lead-time bias
B) Length-time bias

 

 

2. A medical student is performing a chart review to assess the survival duration among a clinic's dialysis patients. They pull charts for all patients they had seen that month who are on dialysis. The survival duration would seem much higher in that student's sample of patients than the literature suggests for dialysis patients due to:

 

A) Lead-time bias
B) Length-time bias

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1. A) Lead-time bias (There was earlier detection with the new guidelines.)

2. B) Length-time bias (Patients with more slowly progressing disease are overrepresented in the student's sample.)

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