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A new blood test to detect prostate cancer is evaluated in 300 male volunteers. A needle biopsy of the prostate gland is done on all men with serum prostate-specific antigen concentrations greater than 5 ng/mL (N less than 4). One hundred men undergo biopsy procedures; 90 are found to have prostate cancer, and five are found to have chronic prostatitis.


Which of the following is necessary to calculate the sensitivity of this test?
(A) Incidence of chronic prostatitis in the general population
(B) Number of men with test results greater than 5 ng/mL and a normal biopsy specimen
(C) Prevalence of chronic prostatitis in the general population
(D) Prostate biopsies of men with test results equal to or below 5 ng/mL

answer is D. please someone expalin it to me
 

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A new blood test to detect prostate cancer is evaluated in 300 male volunteers. A needle biopsy of the prostate gland is done on all men with serum prostate-specific antigen concentrations greater than 5 ng/mL (N less than 4). One hundred men undergo biopsy procedures; 90 are found to have prostate cancer, and five are found to have chronic prostatitis.

Which of the following is necessary to calculate the sensitivity of this test?
(A) Incidence of chronic prostatitis in the general population
(B) Number of men with test results greater than 5 ng/mL and a normal biopsy specimen
(C) Prevalence of chronic prostatitis in the general population
(D) Prostate biopsies of men with test results equal to or below 5 ng/mL

answer is D. please someone expalin it to me
Hi :)
They are essentially asking about TP and FN. To calculate sensitivity you need both. They already gave you TP (90 men tested positive and were confirmed by biopsy). You need FN (men who tested positive but biopsy was negative). Hence - answer D.

It is a little weird, honestly :p Just treat biopsy as confirmation of the disease and then chose the ones who tested + and - on the test we are talking about.

I hope it helps :)
 

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Forget my last post :) Haha, there is nothing better than confusing explanation :)) Anyway, I hope you get it. I got it wrong too so needed think it through.
 

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Forget my last post :) Haha, there is nothing better than confusing explanation :)) Anyway, I hope you get it. I got it wrong too so needed think it through.
thank u joanna. now i understand after ur explanation.. i hope these twisted questions dont come on our exam ;)
 
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