The likelihood that the patient is having cancer - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-27-2010
USMLE Forums Veteran
 
Steps History: 1 + CK
Posts: 234
Threads: 63
Thanked 127 Times in 63 Posts
Reputation: 157
Stats The likelihood that the patient is having cancer

A 55 yr old man visits his physician for urinary complaints, who finds a 1cm nodule on his prostate gland and orders PSA test. PSY > than 4ng/ml is considered abnormal by common standards. The test's sensitivity is 80%, specificity 90%. It's found that 10% of men of his age have prostate cancer on a cross sectional study. The patient's PSA is 7ng/ml. What is ur best estimate of the likelihood that this man has prostate cancer?

A. 13%
B.25%
C.36%
D.47%
E. 58%
F.69%
G.72%
H.81%
Reply With Quote Quick reply to this message



  #2  
Old 06-28-2010
USMLE Forums Guru
 
Steps History: ---
Posts: 487
Threads: 69
Thanked 294 Times in 133 Posts
Reputation: 314
Default

D.47%...??
Reply With Quote Quick reply to this message
  #3  
Old 06-28-2010
USMLE Forums Veteran
 
Steps History: 1 + CK
Posts: 234
Threads: 63
Thanked 127 Times in 63 Posts
Reputation: 157
Default

pls explain how u get ur ans. i want understand it . thank u .
Reply With Quote Quick reply to this message
  #4  
Old 06-28-2010
USMLE Forums Guru
 
Steps History: ---
Posts: 487
Threads: 69
Thanked 294 Times in 133 Posts
Reputation: 314
Default

prevalance of prostate ca. is 10%...means out of 100, 10 people r having ca.
so we hv TP+FN = 10
AND FP+TN = 90 in our 2*2 table
now test sensitivity is 80%... sensitivity=TP/TP+FN
80/100=TP/10
80/100*10=TP
TP=8
SO,FN=10-8=2
AND specificity 90%....specificity=TN/TN+FP
90/100=TN/90
90/100*90=TN
TN=81
SO,FP=90-81=9

NOW they hv asked about PPV...likelihood that pt with positive test actually hv the disease....PPV=TP/TP+FP
=8/17
=0.47
=47%

Hope this helps.....i dont know how to make table here...n m not able to attach any file...hope someone else help u making a table...
Reply With Quote Quick reply to this message
The above post was thanked by:
achistikbenny (06-29-2010), doctorF (06-29-2010)
  #5  
Old 06-29-2010
USMLE Forums Veteran
 
Steps History: 1 + CK
Posts: 234
Threads: 63
Thanked 127 Times in 63 Posts
Reputation: 157
Default

thank u very much .i do understand it now. thank u very much
Reply With Quote Quick reply to this message



Reply

Tags
Biostatistics-Epidemiology

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Cancer screening rasheed USMLE Step 2 CK Bits & Pieces 8 07-12-2016 08:02 AM
Likelihood Ratio kalpana USMLE Step 1 Forum 2 02-17-2016 11:24 AM
Step 3 and Residency Matching Likelihood Steve13 USMLE Step 3 Forum 2 04-19-2010 12:08 PM
Male Breast Cancer rasheed USMLE Step 2 CK Buzzwords 0 02-13-2010 01:57 PM
Cause of cancer cachexia alindawater USMLE Step 1 Forum 1 07-28-2009 09:17 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)