Re: st: First instance of starting and stopping drug

["Paul O'Brien" <paul.obrien@afe2.org.uk>]

The data are longer than that Svend!

id datestart datestop
1 1stJan01
1                  12thJan02
2                  1stFeb01
2  1stFeb01
2                   1stApr04
2  1stApr04
2                   1stJan07
3  1stJan03
3                   censordate

Two points:
the patient can start drug before she attends our clinic
the patient can stop and start on the same day (it is actually a  
hormonal implant, removed at end of life span and another inserted at  
same visit).

We want to measure the continuation rate for the first episode of  
implant use that we inserted ourselves. Data should look like this

id datestart datestop
1  1st Jan01  12th Jan02
2  1st Feb01 1stApr04
3  1stJan03  censordate

So, we want the first datestart on the same row as the next datestop.

Paul


On 3/13/08, Svend Juul <SJ@soci.au.dk> wrote:
Paul wrote:

We have a database of patients on and off a drug in the long form,
some stopping before starting later. I want to do a survival analysis
on the first instance of starting and stopping use under our care, but
have difficulty isolating the first episode of use.

=============================================================

I assume that long form means something like this:

  clear
  input id timeon timeoff
  1 1 3
  1 6 7
  2 1 5
  2 6 9
  end

You want to keep the first treatment period for each id:

  by id (timeon), sort: generate incl = _n==1
  keep if incl==1
  sort id timeon
  list

       +------------------------------+
       | id   timeon   timeoff   incl |
       |------------------------------|
    1. |  1        1         3      1 |
    2. |  2        1         5      1 |
       +------------------------------+


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:  +45 8942 6090
Home:   +45 8693 7796
Email:  sj@soci.au.dk
__________________________________________


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