[R] Kaplan Meier - not for dates

Polwart Calum (COUNTY DURHAM AND DARLINGTON NHS FOUNDATION TRUST) calum.polwart at nhs.net
Mon Nov 7 14:31:32 CET 2011

>  2. The answer will be wrong.  The reason is that the censoring occurs on a time scale, not a $ scale: you don't stop observing someone because
> total cost hits a threshold, but because calendar time does.  The KM routines assume that the censoring process and the event process are on the
> same scale.
> The result can be an overestimation of cost.  See Dan-Yu Lin, Biometrics 1997, "Estimating medical costs from incomplete follow-up data".

Having now skimmed the paper this is long term follow-up.  In my particular case the patients are getting treatment for relatively short periods (median time to stopping treatment will be ~ 9months) and will discontinue treatment relatively quickly (I'd be surprised if anyone is still on treatment 3-4 years out).  I only want the costs of that treatment not the costs for their overall care to death.  I'm not sure how that affects things but  hoping it makes life simpler.



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