Liang, As far as I understand it there is no way to use time varying covariates and a semi-parametric hazard model in NONMEM. The only way I know how to do this is with a fully parametric hazard. In general I prefer the fully parametric approach because it tells you something about the time course of the underlying hazard. The semi-parametric Cox approach completely ignores the underlying hazard. A trade off for statistical convenience versus loss of biological knowledge.
Nick > "Zhao, Liang" wrote: > > Dear All, > > I have the following questions regarding with COX survial model with Time > Dependent Covariate that needs your experience and expertise > > (1) Even we can do it with S-Plus or SAS, it can not be handled by NONMEM, am > I right? If I am wrong, who has started the work? > (2) How to make predictions with time-variant covariates based on COX model > using S-plus or SAS, if not NONMEM? > > The question is asked because certain epidemic diseases are season-sensitive > and none assumption on base hazard is advantageous over parametric > approaches. Thank you in advance! > > Liang Zhao -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:[EMAIL PROTECTED] tel:+64(9)373-7599x86730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/
