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  #1  
Old 11-28-2012
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Default Bias : NBME 2 Concept

A study is conducted to assess the
effectiveness of a new blood
test for early detection of prostate cancer. Ten
thousand healthy men
over the age of 50 years are randomly assigned to
receive either annual
rectal examination or annual screening with the new
blood test. After
5 years, results show that of the 50 men in the blood
test group that
were diagnosed with prostate cancer, 40 were living 2
years after the
diagnosis was made. In comparison, only 15 out of 45
men in the rectal
examination group survived 2 years after being
diagnosed with prostate
cancer. Researchers conclude that the blood test
increases survival
compared with rectal examination. Which of the
following potential flaws
is most likely to invalidate this conclusion?

A) Age of the patients

B) Diagnostic bias

C) Lead time bias

D) Recall bias

E) Type 2 error

I feel this must be Diagnosis Bias due to different test involved for screening
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  #2  
Old 11-29-2012
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Its C) Lead time bias because new blood test for screeing showing improved survival.

Lead time bias:

Early detection of disease showing as increased survival.
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  #3  
Old 11-29-2012
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Aknz...have u done with ur CK exam...??
and where do I find the online NBME form 2 and 4 anwer keys??
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Old 11-29-2012
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Quote:
Originally Posted by Dr.Hunny View Post
Aknz...have u done with ur CK exam...??
and where do I find the online NBME form 2 and 4 anwer keys??
My exam in jan.
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  #5  
Old 11-29-2012
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My exam is in the end of january....is it essential to have KAPLAN Q-bank done before exam?
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Old 11-29-2012
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Quote:
Originally Posted by Dr.Hunny View Post
My exam is in the end of january....is it essential to have KAPLAN Q-bank done before exam?
I think it all depend upon your background knowledge.Some say yes and some say no.
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  #7  
Old 11-29-2012
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but there are two different tests involved for the same disease. so already a bias would come because of two different diagnostic test involved. Also the age of the patient used in this study is same in both samples so in both cases I think if the diagnosis is done at the same time they would have survived somewhat similarly but its the difference in test involved which is changing the survival outcome. So may be blood testing would diagnose a case better than DRE.
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