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From |
Marcos Vinicius <bioestatistico@inbox.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: KM curve adjusted by the Inverse Probability of Treatment Weights(IPTW) |

Date |
Thu, 20 Dec 2012 11:19:42 -0800 |

Thank you Adam.Helped a lot. > -----Original Message----- > From: adam.olszewski@gmail.com > Sent: Thu, 20 Dec 2012 12:31:35 -0500 > To: statalist@hsphsun2.harvard.edu > Subject: Re: st: KM curve adjusted by the Inverse Probability of > Treatment Weights(IPTW) > > Hi Marcos, > In Stata, you just need to stset your dataset indicating appropriate > weights: > stset time [pw=iptw], fail(remission) > > Then you can graph anything you want, and the weight adjustment is > done automatically: > sts graph, by(tx) > > I'm not going into the intricacies of what such graphs might or might > not represent, since I trust you understand them. Curve comparison can > be only done with a Cox regression (or another regression model if you > prefer, such as Royston-Parmar). You will not be able to use the efron > or exact tie adjustment. > > sts test tx > which should be the same as > stcox test > > I am not a statistician and do not understand very well why/if > non-parametric tests can or cannot be done with pweighted data, but > simple logrank certainly cannot be done and Stata will refuse to > perform it (it will default to Cox). On the other hand, the > -stpepemori- (available through SSC) command from Enzo Coviello works > in a pweighted dataset and I had at least one expert declare that it > should be valid to use. If any of our statisticians on the list can > (p)weigh in on the subject I would be delighted to hear! > > Great reference: > Cole, S. R. and M. A. Hernan (2004). "Adjusted survival curves with > inverse probability weights." Comput Methods Programs Biomed 75(1): > 45-49. > And of course the famous: > Hernan, M. A., et al. (2000). "Marginal structural models to estimate > the causal effect of zidovudine on the survival of HIV-positive men." > Epidemiology 11(5): 561-570. > > Adam Olszewski > > On Thu, Dec 20, 2012 at 11:55 AM, Marcos Vinicius > <bioestatistico@inbox.com> wrote: >> Hello, >> I would like to generate a Kaplan Meier curve >> adjusted(controlled/corrected) by the Inverse Probability of Treatment >> Weights(IPTW). >> Supose I have a dataset with columns: tx=treatment (0/1) , >> ps=propensity score weig= Inverse Probability of Treatment Weights >> (iptw),time (=survival time)remission(1/0) (0=censored), >> In IPTW, individuals are weighted by the inverse probability of >> receiving the treatment that they actually received. >> In SAS I tried this code but it is not working although it is indicated >> in the SAS/STAT >> 12.1 User’s Guide The LIFETEST Procedure (Chapter) >> Someone could help me with a Stata code to produte and compare 2 Km >> curves according to treatment group but adjusted by iptw(weig) >> proc lifetest method=km data=ps plots = (survival ); >> >> time time*remission(0); >> weight weig; >> survival out=surv_data conftype=loglog ; >> /*weight weig;*/ >> ODS EXCLUDE ProductLimitEstimates Means LogrankHomCov WILHOMCOV HomStats >> TaroneHomCov PetoHomCov Rank HomTests ; >> /*weight weig;*/ >> strata tx; >> /*weight weig;*/ >> run; >> [ >> Error message from SAS log >> ERROR 180-322: Statement is not valid or it is used out of >> proper order. >> >> >> After program the propensity score weight , also referred to as the >> inverse probability oftreatment weight (IPTW)( weig in the SAS code) I >> tried to use the weight statatement from proc Lifetest to produce a >> Kaplan-Meier curve adjusted by iptw. It is not working. >> Someone could help me in the code implementation or guide another way >> to produce the KM curve adjusted by propensity score?: >> Many thanks, >> Vinicius. >> >> ____________________________________________________________ >> GET FREE SMILEYS FOR YOUR IM & EMAIL - Learn more at >> http://www.inbox.com/smileys >> Works with AIM®, MSN® Messenger, Yahoo!® Messenger, ICQ®, Google Talk™ >> and most webmails >> >> >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ ____________________________________________________________ GET FREE SMILEYS FOR YOUR IM & EMAIL - Learn more at http://www.inbox.com/smileys Works with AIM®, MSN® Messenger, Yahoo!® Messenger, ICQ®, Google Talk™ and most webmails * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**Re: st: KM curve adjusted by the Inverse Probability of Treatment Weights(IPTW)***From:*Adam Olszewski <adam.olszewski@gmail.com>

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