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Re: st: Left truncation in survival: how to use stset origin and enter


From   "Svend Juul" <SJ@SOCI.AU.DK>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Left truncation in survival: how to use stset origin and enter
Date   Fri, 11 May 2007 16:59:02 +0200

Diego wrote:
 
I have a question regarding the use of origin and enter
option when stsetting data for a survival analysis with
left truncation (delayed entry). 
 
I have the diagnosis date and the exam date for all my
patients. The exam date can be also few years after the
diagnosis date.

Obviously the diagnosis date is the date patients start
to be at risk (end-point: death) but the aim of the
study is to look at the prognostic value of the lab
examination we do on our study population, and the follow-
up in that case is only 3 years (where the follow-up
from the diagnosis time is 7-8 years). 
 
How should I stset my data to take into account the
diagnosis date but to look at the prognostic value of
the exam date ?
 
------------------------------------------------------------
 
I don't think this should be considered a case of delayed
entry: The prognostic value of the lab examination applies
to the time after the examination, and the date of diagnosis
is hardly relevant in that context. So you could:
 
   generate risktime = enddate - examdate
   stset risktime , failure(...)
 
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 
_________________________________________________________ 

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