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try nbme. EXpalin

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nadiabarati

06/12/06 - 08:29 PM

A 35-year-old woman at 18 weeks' gestation has an increased serum α-fetoprotein concentration. Which of the following has the greatest influence in determining the predictive value of this test for neural tube defects? A)Concentration of α-fetoprotein in maternal serum

B)Maternal history of monozygotic twin pregnancies

C)Prevalence of neural tube defects in the population in question

D)Sensitivity of the test

E)Specificity of the test

Geroo
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06/12/06 - 09:15 PM

I think c.

as increase previlance always increases positive predictive value

robin082006
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06/12/06 - 09:33 PM

C

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alexaE
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06/13/06 - 12:03 AM

E

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mjl1717
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06/13/06 - 01:22 AM

Geroo wrote:
I think c.

as increase previlance always increases positive predictive value

true, it also seen in some liver disease and as i remember germ cell tumors

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alexaE
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06/13/06 - 02:18 AM

it clearly says "this test"
specificity confirms a disease
if a test has 100% specificity, it has 100% PPV
or do i understood...

why C again? please explain some more

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leen
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06/13/06 - 01:33 PM

specificity

robin082006
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06/13/06 - 09:25 PM

The patient tested positively, the question asks about positive predictive value---> which is most affected by the Prevalence.

Hope this help.

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