R help - May 2005 - 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?

Is the frailty distribution updated in the left-truncated case?

Or is the frailty function only built for time-constant covariates and left
truncated data?

Thank you, 

Stef.

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On Tue, 31 May 2005, Stefan Pohl wrote:
> 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