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13 Posts

nadiabarati

06/24/06 - 07:02 PM

A 35-year-old woman at 18 weeks' gestation has an increased serum á-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 á-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

mjl1717
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06/24/06 - 07:56 PM

answer-c prevalence

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sridevibandaru24
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06/25/06 - 03:16 PM

leen
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06/25/06 - 09:00 PM

robin082006
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06/25/06 - 09:02 PM

C, this q has been discussed

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yonela78
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06/27/06 - 02:20 PM

I agree that the PPV increases when prevalence increases. But there is also a relation between PPV and specificity: high specificity of the test implies high PPV ...because high Sp means few FP, and few FP means high PPV. So, for me C is as good as E. Anyone thinks the same?

alpha12
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07/28/06 - 03:09 PM

I was thinking E. they're talking about influence on the test PPV and not the consequence of change in PPV. I think the specificity of the test has more influence on the PPV than the prevalence. What do u guys think?

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vanshita
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07/30/06 - 09:19 PM

i think answer E

docswapna
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09/27/06 - 11:15 AM

c is the ans..

NE
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10/30/06 - 10:41 AM

#10

It is C- the Sp and Ss depend only the test itself but the PPV is depending to the prevalence.

smal
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11/05/06 - 11:02 AM

#11

ppv is dependent on prevelance of disease.
so definetly c.

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ashfaque
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11/08/06 - 02:05 AM

#12

ans C

titly
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03/18/07 - 03:38 AM

#13

E COZ THE GREATEST PPV OCCURS AT THE POINT OF MAX SPECIFICITY nod

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