Re: Parameterization!!!

From: "Jean-Xavier.Mazoit@kb.u-psud.fr" <jean-xavier.mazoit@kb.u-psud.fr> Subject: Re: Parameterization!!! Date: Thu, 10 May 2001 08:25:33 +0200 Dear Nick, I would have a less definite opinion. Indeed, if you think in term of interindividual variability, it seems better to reparameterize your model with more physiologic parameters such as volume and clearance, and then use an error structure (the ETAs) directed to these parameters. However, 1) models are just a pale description of reality, and 2) it is important to remember that the TRANS utilities (other than TRANS1) transform CL AND V back into rate constants ! Linear models (which are approximations of Michaelis-Menten kinetics and diffusion processes) are built with rate constant, not clearance. I think that it might be dangerous to always use your principles when doing resampling, especially when one bootstraps the errors, not the data. If you prefer to reparameterize your models to CL and Vss, why do not use the "non compartmental" approach which is based on the same principles of linearity ? Jean Xavier Mazoit MD, PhD Laboratoire d'Anesthésie Université Paris-Sud Faculté de Médecine du Kremlin-Bicêtre F-94276 Bicêtre France Tel. (33) (0)1 49 59 67 35-37 (33) (0)1 45 21 34 41 (Hopital) Fax (33) (0)1 45 21 28 75 e-mail Jean-Xavier.Mazoit@kb.u-psud.fr