NBME 2b2 q 25 - im2080

[ArchivalUser]

can somebody help?
An ELISA is used to detect Chlamydia trachomatis
infection in patients
seen at a family planning clinic. In the first 500
patients, cultures
are also done to check the accuracy of the ELISA. The
results are
listed below:

Chlamydia culture
+ -

ELISA + 38 5
- 2 455

Which of the following is the positive predictive
value of the ELISA?

A
) 2/40

B
) 5/43

C
) 38/40

D
) 38/43

E
) 38/493

[ArchivalUser]

TP = 38 FP= 5
FN = 2 TN=455
I DID CHOSE D BUT in the answer key it says C
thanx for anyone answer

[ArchivalUser]

anyone help?

[ArchivalUser]

I haven't taken the exam online so i don't know what the table looked like. But according to the data you gave here for TP, FP, the answer should be D.

The general rule for this is PPV=TP/TP+FP= 38/43

Someone may explain why C though.

[ArchivalUser]

Pls d ans is D,thats y u shld take d exam online,this question is so simple and straight forward.PPV=TP/TP+FP