RE: Covariate Model Selection

From: "Piotrovskij, Vladimir" <vpiotrov@janbe.jnj.com> Subject: RE: Covariate Model Selection Date: 11 Mar 1998 03:29:00 -0500 Dear Peter, The correct syntax for proportional - additive error model is Y = F*EXP(EPS(1)) + EPS(2) or, equivalently, Y = F*(1 + EPS(1)) + EPS(2) Another point to comment: You write you have steady-state data and a substantial part of your measurements are at trough. I don't think you have enough information to characterize effects of covariates like BSA on the volume of distribution. Trough level at steady-state is mainly determined by CL. Then, CL and V are usually highly correlated. You'd better concentrate on looking for covariates affecting CL. After including all of them significantly improving the fit you can spend some time plotting ETA(V) vs. covariates. And if you are lucky... Hope this helps Vladimir ---------------------------------------------------------------------- Vladimir Piotrovsky, Ph.D. Janssen Research Foundation Clinical Pharmacokinetics B-2340 Beerse Belgium Fax: +32-14-605834 Email: vpiotrov@janbe.jnj.com vpiotrov@janbelc1.ssw.jnj.com