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st: capturing full survival time with KM -sts graph-


From   Michael McCulloch <mm@pinest.org>
To   Statalist <statalist@hsphsun2.harvard.edu>
Subject   st: capturing full survival time with KM -sts graph-
Date   Sun, 11 Nov 2007 19:13:31 -0800

Hello Statalist members,
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?
Thank you kindly,


-- 

Michael McCulloch
Pine Street Foundation
124 Pine St., San Anselmo, CA 94960-2674
Tel:	(415) 407-1357
Fax:	(415) 485-1065
mcculloch@pinestreetfoundation.org

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