It's an Epid q

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It's an Epid q

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10 Posts

ELM
Forum Guru

Topics: 28
Posts: 936

01/19/05 - 03:00 PM

A 55 year old man visits his primary care physician with a complaint of urinary infrequency. Examination finds a 1cm nodule on his prostate gland. The physician orders a PSA serum test. By common stantards, a PSA level greater than 4 ng/ml is considered abnormal. Using this standart, this test has a sensitivity of 80% and a specificity of 90%. A recently published article found that in a cross-sectional study, 10% of men of this age have prostate cancer. The result on the patient's PSA is 7 ng/ml. What is your best estimate of the likelihood that this man actually has prostate cancer?
a. 13%
b. 25%
c. 69%
d. 47%
e.72%

Anyone??

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ELM

mash
Forum Fanatic

Topics: 147
Posts: 1,326

01/19/05 - 03:43 PM

47%

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I hear and I forget. I see and I remember. I do and I understand.
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ELM
Forum Guru

Topics: 28
Posts: 936

01/19/05 - 04:30 PM

Mash,
How is it going?
When are you taking the test?
Hey how did you get this 47%? Explain your calculation please. My brain does not work for math.....can't change it nomatter what i do. :|
Good to see you!

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ELM

mash
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Topics: 147
Posts: 1,326

01/19/05 - 04:56 PM

hey elm,

10% is the ds prevalence
suppose u r calculating fr 100 people dat means 10 ve the ds
==>TP+FN=10
sen=80%
==> TP/TP+FN=80/100==>TP=8
so, FN =2

TN+FP=90
specificity is 90%
==>TN/TN+FP=90/100==> TN=81
==>FP=9
we ve to calculate PPV
=TP/TP+FP= 8/8+9=47%
wats the ans?

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I hear and I forget. I see and I remember. I do and I understand.
--Confucius

ELM
Forum Guru

Topics: 28
Posts: 936

01/19/05 - 05:28 PM

The answer is 47% my dear.
You got it. :shock:...i got it now! Thanks grin

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ELM

mash
Forum Fanatic

Topics: 147
Posts: 1,326

01/19/05 - 08:53 PM

"ELM" wrote:
Mash,
How is it going?
When are you taking the test?
Good to see you!

hey elm, gud to see u too.
If all goes well i ll take it by march end. So, im keeping my fingers crossed.
how abt u? how is ur prepn going?

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I hear and I forget. I see and I remember. I do and I understand.
--Confucius

ELM
Forum Guru

Topics: 28
Posts: 936

01/19/05 - 08:58 PM

Mash,
I am doing all right, trying to keep busy.
Doing some readings right now, and hopefully start UW in the next week or so.
Let's putting more qs up here, so we all learn.
Have you started UW or kaplan q bank yet?

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ELM

mash
Forum Fanatic

Topics: 147
Posts: 1,326

01/19/05 - 09:48 PM

yeah, we can ve discussions dat way..
i m doin uw q bank...and plan to do kaplan q bank next mth.
gud luck!

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I hear and I forget. I see and I remember. I do and I understand.
--Confucius

tasneembanu
Forum Guru

Topics: 96
Posts: 545

01/20/05 - 04:08 PM

Hi Mash and ELM,

how's ur studies goin on?even im planning to take my exam by the end of March,hopefully.right now,revising a bit if medicince and then planning to take USMLEWORLD.

Mash,thanks for explaning.

all the best guys.

Tasneem.

noelle
Forum Elite

Topics: 59
Posts: 226

01/21/05 - 03:46 PM

#10

47

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