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From   owner-statalist@hsphsun2.harvard.edu
To   statalist@hsphsun2.harvard.edu
Date   Tue, 1 Mar 2005 21:37:53 +0000

Dear list members,

I have troubles to get Stata doing what I want (I have done similar already with
SAS but can't get it working with Stata).
I have a data set with one or more hospital admissions each. The admission could
have been because of the occurance of a specific disease (here coded as event).
I want to code every event as an first event (incident case), if the person was
not admitted to hospital for the same reason in the previous 10 (or 5) years
before.
The idea was, to do some sort of look back, if an event is an incident case. I
wanted to check for every patient separately (by id:...):
1. has the current obs an event? If not, continue with the next observation; if
yes, step 2.
2. check if the next observation has an event too? If not, check the second next
observation (and so on) for an event - till end of observations for this person.
If an event occurs, continue with step 3.
3. check the time between the both events. If the time between the both events
is 10(5) years or more the event (from step 1) is tagged as incident case. If
the time difference is less then 10(5) years the event from step 1 is not
tagged as a case and we continue the same procedure starting with step 2 again
with the new event from step 3.

The dataset looks like that:

id  startdate  enddate    event stay adm_total
001 23/06/2004 13/07/2004     1    1         7
001 17/01/2004 28/02/2004     1    2         7
001 23/10/2002 24/10/2002     0    3         7
001 03/05/1998 25/05/1998     1    4         7
001 12/01/1994 12/03/1994     0    5         7
001 12/04/1976 24/04/1976     0    6         7
001 12/04/1976 24/04/1976     1    7         7
002 04/02/2003 28/02/2003     0    1         2
002 11/10/2000 18/10/2003     0    2         2
003 15/03/2004 26/03/2004     1    1         6
003 02/04/2003 04/04/2003     0    2         6
003 08/11/2001 12/11/2001     0    3         6
003 26/05/1999 31/05/1999     0    4         6
003 30/01/1994 12/03/1994     0    5         6
003 12/06/1976 24/04/1976     0    6         6

and the result should look like that with 10 years and 5 years look back:

id  startdate  enddate    event stay adm_total case10y case5y casedate10y ...
001 23/06/2004 13/07/2004     1    1         7       0      0  .
001 17/01/2004 28/02/2004     1    2         7       0      1  .
001 23/10/2002 24/10/2002     0    3         7       0      0  .
001 03/05/1998 25/05/1998     1    4         7       1      1  03/05/1998
001 12/01/1994 12/03/1994     0    5         7       0      0  .
001 12/04/1976 24/04/1976     0    6         7       0      0  .
001 12/04/1976 24/04/1976     1    7         7       1      1  12/04/1976
002 04/02/2003 28/02/2003     0    1         2       0      0  .
002 11/10/2000 18/10/2003     0    2         2       0      0  .
003 15/03/2004 26/03/2004     1    1         6       1      1  15/03/2004
003 02/04/2003 04/04/2003     0    2         6       0      0  .
003 08/11/2001 12/11/2001     0    3         6       0      0  .
003 26/05/1999 31/05/1999     0    4         6       0      0  .
003 30/01/1994 12/03/1994     0    5         6       0      0  .
003 12/06/1976 24/04/1976     0    6         6       0      0  .

I have tried foreach but first you can not combine it with by...: and second I
could not use variables (to account that for each person I has a different
number of admissions) with it (something like: foreach x = stay/adm_total).
It might be easier to reduce the data set to these only with an event first, but
this might reduce the application in a general manner (e.g. stay and adm_total
have to be recalculated for evey new sort of event, if realy needed).

id  startdate  enddate    event stay adm_total
001 23/06/2004 13/07/2004     1    1         7
001 17/01/2004 28/02/2004     1    2         7
001 03/05/1998 25/05/1998     1    4         7
001 12/04/1976 24/04/1976     1    7         7
003 15/03/2004 26/03/2004     1    1         6

Does anyone had to write a similar program in Stata and a solution for this
problem ready or any idea how I can get my look back via looping through all
remaining observations of one person to work?

Thank you for any comments and help,
Markus

/**********************************
Markus Steiner, MSc
Clinical Research Fellow
Room 732, Public Health Sciences
The Medical School, Teviot Place
Edinburgh EH8 9AG
Tel: +44-(0)131-650 3204
Mob: +44-(0)7910-22 9925
Fax: +44-(0)131-650 6909
EMail: markus.steiner@ed.ac.uk
EMail: steiner@epi-centre.net
**********************************/


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