For more on data preparation for survival analysis see lesson 3 in
Stephen Jenkins' series of lectures on survival analysis:
http://www.iser.essex.ac.uk/teaching/degree/stephenj/ec968/
-- Maarten
--- Svend Juul <[email protected]> wrote:
> Michael McCulloch wrote:
>
> I'm applying -sts graph- to a set of survival data, in which study
> ends at 10 years. However, the Kaplan Meier plot I create doesn't
> reflect people who survived till study's end.
>
> Below are sample data, prepared with
> . stset datedied, failure(failed) origin(datedx) scale(30.4375)
>
> id datedx datedied datelost studyend _t
> 5 01may1992 . . 31oct1997 .
> 8 01sep1991 01sep1996 . 31oct1997 60
> 22 01jun1991 . . 31oct1997 .
> 33 01jan1989 . 01jan1996 31oct1997 .
>
> The following command will not show the subjects who survived till
> study's end:
> . sts graph
>
> Note that _t correctly shows 60 month survival for:
> subject #8, who lived 5 years
>
> However, note that _t shows no survival time for:
> subjects #5 and #22, who were still alive at study end
> subject #33, who lived 7 years.
>
> I don't want to simply replace _t with the date calculation
> "datelost-datedx", because _t for those censored subjects will be
> lost if I again -stset-.
>
> I also don't want to simply replace datedied with studyend, because
> those subjects censored at study end will look like they'd died on
> the KM plot.
>
> How is a situation like this handled?
>
> ------------------------------------------------------------------
>
> You need one variable containing the time at observarion end (death
> or
> censoring) and a dichtomous event variable. Here is an example:
>
> clear
> input id str9 ddx str9 ddied str9 dlost str9 stend
> 5 01may1992 . . 31oct1997
> 8 01sep1991 01sep1996 . 31oct1997
> 22 01jun1991 . . 31oct1997
> 33 01jan1989 . 01jan1996 31oct1997
> end
>
> version 9 // Date functions and formats are different in
> Stata
> 10
>
> generate datedx = date(ddx,"dmy")
> generate datedied = date(ddied,"dmy")
> generate datelost = date(dlost,"dmy")
> generate studyend = date(stend,"dmy")
> egen enddate=rowmin(datedied-studyend)
> format datedx-enddate %d
> generate risktime=enddate-datedx
>
> generate died=0
> replace died=1 if datedied<.
>
> // or: generate died = datedied<.
>
> stset risktime, failure(died==1) id(id)
>
> sts list
>
> 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: [email protected]
> __________________________________________
>
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
___________________________________________________________
Yahoo! Answers - Got a question? Someone out there knows the answer. Try it
now.
http://uk.answers.yahoo.com/
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
