How to create KM curves and Cox PH model with time-dependent covariate

SeaMoon_168 — Mon, 25 Jul 2022 21:40:49 GMT

Some patient received an treatment as treated group and some did not as control group. In order to consider "immortal time bias", I coded the treatment as a time-dependent covariate.

For example, there are two patients:

P1 received the treatment 30 days after the start of this study and died 30 days after receiving the treatment.

P2 did not received the treatment and survived at the end of this study (80 days).

Here I code the data as follow:

ID	Treatment	Time	Death
P1	0	30	0
P1	1	30	1
P2	0	80	0

Then I just used SAS code to create KM curves

/*Survival curve*/

proc lifetest data=treatment;

time Time*Dearg(0);

strata Treatment;

run;

and run Cox PH model

/*Cox PH Model*/

proc phreg data=treatment;

model Time*Death(0)=treatment;

run;

Re: How to create KM curves and Cox PH model with time-dependent covariate

SeaMoon_168 — Thu, 28 Jul 2022 00:46:49 GMT

I am not sure what I did is right or not? Could anyone who dealt with, immortal time bias, give me some advice on it? Thanks.

topic How to create KM curves and Cox PH model with time-dependent covariate in Statistical Procedures

How to create KM curves and Cox PH model with time-dependent covariate

Re: How to create KM curves and Cox PH model with time-dependent covariate