[R] Apparently Conflicting Results with coxph
therneau at mayo.edu
Wed Oct 3 18:21:54 CEST 2007
> I thought about this some more, and I'm not sure that possibility is
> "to blame." In my time-dependent model, I don't think I'm doing
> anything different than is done for transplant in the Stanford
> Heart Study (the often used example for this kind of time-dependent
> covariate). As in my case, you would not transplant a dead patient.
> So, I remain puzzled as to why my model is misbehaving.
The Stanford Heart Study, quoted in nearly every survival book as you say, is
a bit of an anomaly. At the time it was run a good tissue match between the
donor heart and the recipient was considered very important. When a donor
became available, the best match (or near best) among those waiting was chosen
to recieve it. Since the donor genetics are unpredictable, this is essentially
equal to a random pick from those waiting. The Stanford study is nearly alone
in examples of time-dependent treatment in not having selection effects.
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