Re: Model building question

From: "Janet R. Wade" janet.wade@exprimo.com Subject: Re: [NMusers] Model building question Date: Tue, March 1, 2005 12:41 pm Hi Jeff and Mark I agree with the idea that we should consider if the different models we arrive at (depending upon the route we take to that final model) would result in different inferences. In the work Mark referred to I could indeed end up with two different models, one a one compartment model with three covariates and one a two compartment model with one covariate (simulated data). I found the same issue when I analysed two real data sets, different structural models but with the same total number of parameters due the different number of covariates in the two 'final' models for each compound. The paper in question (Wade et al., Interaction between the choice of structural, statistical and covariate models in population pharmacokinetic analysis. J. Pharmacokin. Biopharm., 22, 165-177) did not address if the predictions of the two models would differ, but some unpublished work I did after writing the paper did look at the predictions that they gave. The results were similar and would not have resulted in different dosing instructions (my opinion only). Obviously peaks and troughs were slightly different and that could be important for drugs with a narrow therapeutic index. Kind regards Janet