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Re: st: comparison of diagnostic procedures


From   htzavara@med.uoa.gr
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: comparison of diagnostic procedures
Date   Wed, 7 Sep 2005 21:05:58 +0300

&Agr;&rgr;&khgr;&igr;&kgr;&oacgr; &mgr;&eeacgr;&ngr;&ugr;&mgr;&agr; &agr;&pgr;&oacgr;  Svend Juul <SJ@SOCI.AU.DK>:

> htzvara (?) wrote:
> 
> i have one variable which represents if the patient has the disease (coding:
> 0-
> 1)--and this is standard.
> Additionally i have 12 more variables which represents the outcome of 12
> different diagnostic procedures (coding: 0-1 for all of them).I want to find
> which is the best diagnostic procedure. I calculate the sensitivity and
> specificity and their confidence intervals for each of them. If the
> confidence
> interval for the sensitivity of one diagnostic procedure do not overlap the
> confidence interval for the Se of another diagnostic procedure then the
> difference is significant.
> Is there any test to perform and give p_value? Is there a need to make a
> correction for multiple comparisons.?
> 
> ----
> 
> It is not quite clear to me what you want. If it is to find the single test
> that has the "best" predictive value, try Paul Seed's -diagt-  (findit
> diagt). However, you must look at both sensitivity and specificity to get a
> meaningful assessment.
> 
> I am not sure why you want to test whether the sensitivity of two tests are
> significantly different. And the confidence interval comparison you describe
> is quite insensititive.
> 
> Would this show what you need:
> Make a logistic regression followed by -lroc- (ROC analysis):
>    . logistic disease test1-test12
>    . lroc
> 
> You might then try to remove tests to see whether removal makes a difference
> to the AUC (area under curve).
> 
> Hope this helps
> Svend
> 
> ________________________________________________________
> 
> Svend Juul
> Institut for Folkesundhed, Afdeling for Epidemiologi
> (Institute of Public Health, Department of Epidemiology)
> Vennelyst Boulevard 6
> DK-8000 Aarhus C,  Denmark
> Phone, work:  +45 8942 6090
> Phone, home:  +45 8693 7796
> Fax:          +45 8613 1580
> E-mail:       sj@soci.au.dk
> _________________________________________________________
> 
> Thank you very much for your help.
 I know about diagt and i used it to obtain the sensitivity - specificity.
 Roc analysis cannot help as the variables which represents the diagnostic 
tests are not continuous but dichotomous (0-1).Even if i can see, which test 
has the best se-sp i want to perform a test to prove it.

thank you again.
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> 


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