Re: [R] hazard ratio of interaction Cox model

From: Frank E Harrell Jr <f.harrell_at_vanderbilt.edu>
Date: Tue, 18 Dec 2007 06:41:18 -0600

Giulia Barbati wrote:
> Dear Forum,
> I have a question about interaction estimate in the Cox model:
> why the hazard ratio of the interaction is not produced in the summary of the model?
> (Instead, the estimate of the coefficient is given in the print of the model.)

The 'hazard ratio of the interaction' is not well defined. Decide what hazard ratio you want to estimate, then ask summary to compute that, e.g.

summary(modINT, XX_PR=c(1,3), XX_DISF=2)

will estimate the 3:1 XX_PR hazard ratio at XX_DISF=2

Frank Harrell

>
>
> # Example:
>
> modINT <-cph( Surv(T_BASE, T_FIN,STATUS)~ NYHA + ASINI + RFP + FE_REC + XX_PR*XX_DISF)
>
> print(modINT)
>
>
> coef se(coef) z p
> NYHA=2 1.254 0.584 2.15 0.031767
> ASINI 0.665 0.409 1.62 0.104247
> RFP=2 0.725 0.704 1.03 0.302578
> FE_REC=2 -1.637 0.810 -2.02 0.043331
> XX_PR 2.189 0.649 3.37 0.000748
> XX_DISF 3.233 1.000 3.23 0.001222
> XX_PR * XX_DISF -2.852 1.280 -2.23 0.025852
>
> summary(modINT)
>
> Effects Response : Surv(T_BASE, T_FIN, STATUS)
>
> Factor Low High Diff. Effect S.E. Lower 0.95 Upper 0.95
> ASINI 2.0725 2.85 0.7775 0.52 0.32 -0.11 1.14
> Hazard Ratio 2.0725 2.85 0.7775 1.68 NA 0.90 3.13
> XX_PR 0.0000 1.00 1.0000 2.19 0.65 0.92 3.46
> Hazard Ratio 0.0000 1.00 1.0000 8.92 NA 2.50 31.86
> XX_DISF 0.0000 1.00 1.0000 3.23 1.00 1.27 5.19
> Hazard Ratio 0.0000 1.00 1.0000 25.35 NA 3.57 179.88
> NYHA - 2:1 1.0000 2.00 NA 1.25 0.58 0.11 2.40
> Hazard Ratio 1.0000 2.00 NA 3.50 NA 1.12 11.00
> RFP - 2:1 1.0000 2.00 NA 0.73 0.70 -0.65 2.10
> Hazard Ratio 1.0000 2.00 NA 2.07 NA 0.52 8.20
> FE_REC - 2:1 1.0000 2.00 NA -1.64 0.81 -3.23 -0.05
> Hazard Ratio 1.0000 2.00 NA 0.19 NA 0.04 0.95
>
> Adjusted to: XX_PR=0 XX_DISF=0
>
>
>
>
> ____________________________________________________________________________________
> Be a better friend, newshound, and
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University

______________________________________________
R-help_at_r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Received on Tue 18 Dec 2007 - 12:46:14 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Tue 18 Dec 2007 - 13:30:19 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.