Biostatistics Q.......2 - psychmledr

[ArchivalUser]

A 55 yr old man visits his Doc with urinary obstructive symptoms, and a 1 cm palpable nodule on his prostate. The PSA is 7 ng/ml. By common standards, a level greater than 4 ng/m is considered abnormal. Using this standard, this test has a sensitivity of 80% and a specificity of 90%. A recently published epidemiologic article found that in a cross-sectional study, 10% of men at this age have prostate cancer. What's your best estimate on the likelihood that this man actually has prostate cancer?

(a) 13%,
(b) 25%,
© 36%,
(d) 47%,
(e) 58%,
(f) 69%,
(g) 72%,
(h) 81%

[ArchivalUser]

Likelihood ratio = sensitivity/1-specificity
= 80/100-90
=80%

Is the answer H? Probably I am missing something

[ArchivalUser]

No, it is not

[ArchivalUser]

yes i agree with drock..

80/1-90...i m getting 8..!! so i 'll just say 80%...
messed up my calculation somewhr i guess..

in this do we remove the % n add 100???

can some1 solve it for me.

[ArchivalUser]

do we use some other formula?? whr r u ...;(

[ArchivalUser]

Based on the fact that 10% of his age men have prostate cancer (10 out of 100 men) and on the given sensitivity, specificity, you construct the following table:



CANCER

test + - total
+ 8 9 17
- 2 81 83
total 10 90

and then you calculate ppv: 8/17=47% answer d

thanks for the question and gl to all of us

[ArchivalUser]

test Cancer + .....- .........total
+...............8 ......9 .........17
- ...............2 .....81 ........83
total.........10..... 90

I hope the table posts better this time

[ArchivalUser]

is it d) 47%??

[ArchivalUser]

q asking abt PPV
10% population has disease so 10 out of 100

test--------------disease present-----------disease absent

positive----------- 8[sensitivity]-------------9[specificity]

negative-----------2[FN]--------------------83


PPV=TP/TP+FP
==8/8+9
=47%

[ArchivalUser]

wow. indeed 47% i broke my head for this...now lemme get back to UW!!