cliffh
Topics: 5
Posts: 24
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This is a question from NBME form 3:
If 1 person in 10,000 with a negative PPD skin test has active TB, and 1 person in 100 with a positive PPD skin test has active TB, which of the following is the estimated relative risk of active tuberculosis in persons with a positive PPD skin test?
A) 1
B)9.9
C)100
D)1000
E)10,000
My answer is C.
What do you think?
Edited by cliffh on 02/03/06 - 09:50 PM
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| drk1980
Forum Guru
Topics: 147
Posts: 1,038
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my answer is C too.
can u show ur calc plz?
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| cliffh
Topics: 5
Posts: 24
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This is what I did:
(1/100) / (1/10,000)=100
The reason that I feel fishy about the answer is that the question asks about "relative risk" which is for cohort study (an observational study). But from the question stem, the PPD test is not an observational study, not a prospective study, and I feel the sensitivity, specificity, the PPV and NPV should be used.
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