Shared Frailty in survival package (left truncation, time-dep. covariates)

Dear list,

I want o fit a shared gamma frailty model with the frailty specification 
in the survival package.

I have partly left-truncated data and time-dependent covariates. Is it 
possible to combine these two things in the frailty function. Or are the 
results wrong if I use data in the start-stop-formulation which account 
for delayed entry?

It should work: as usual in the Cox model you get left-truncation and 
time-dependent covariates for free, since the partial likelihood only 
considers one risk set at a time.  You do need to make sure you specify 
the correct id variable, of course, and left truncation may reduce the 
amount of information available for estimating the frailty.


 	-thomas