Hi all,
I am trying to detect association between a covariate and a disease outcome
using R. This covariate shows time-varying effect, I add a time-covariate
interaction item to build Cox model as follows:
COX <-
coxph(as.formula("Surv(TIME,outcome)~eGFR_BASE+eGFR_BASE:TIME"),ori.data);
coef exp(coef) e(coef)
z p
eGFR_BASE 6.40 603.5133 0.3702 17.3 0
eGFR_BASE:TIME -3.41 0.0329 0.0772 -44.2 0
But the result seems very different from that got by SPSS:
B SE
Wald df Sig. Exp(B)
eGFR_BASE -13.603 .548 616.007 1
.000 .000
T_COV_*eGFR_BASE .860 .115 55.859 1 .000
2.362
so my questions are :
1, Is it correct to deal with time dependent covariate in Cox regression using
R? if not, how to do it ?
2, How T_COV_ was calculated in SPSS, and is it the same with the survival time?
Many thanks.
GZ
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