NONMEM Users Network Archive

Hosted by Cognigen

Your suggestions/thoughts needed on allometric base or final model

From: Hong-Guang Xie <hongg.xie>
Date: Fri, 11 Jul 2008 12:36:00 -0400

Dear NMusers:

As you know, body weight is an important covariate that is integrated into
the final or covariate model in some cases. When analyzing pediatric pop PK
data, body weight-based allometric power model is used frequently. By
definition, base model is a model without any covariates. But, in the
literature on the population PK in pediatrics, I noted that body weight is
added to the structural model (following the principles of allometry) befor=
starting the covariate model building in some but not in all studies. That
means that some models are called allometric base models and others are not=
What are their differences? For the allometric base model, body weight has
been added into the base model regardless of whether it is an important
covariate (in some cases, body weight is not). If body weight is not an
important covariate as determined by further covariate model building, is
there still the need to add body weight into the final allometric model
(if its corresponding base model is one without a body weight-associated
allometric component)? Logically, such a need seems to be not reasonable.
How to deal with this conflict? Is there an almost agreeable thought on thi=
issue in our community?

Thank you,


Received on Fri Jul 11 2008 - 12:36:00 EDT

The NONMEM Users Network is maintained by ICON plc. Requests to subscribe to the network should be sent to:

Once subscribed, you may contribute to the discussion by emailing: