RE: Sparse (pediatric) and rich (adult) data

Leonid > I hope that you do not dispute that in this particular case > you need to use adult data (50 full profiles) rather than > discard them and use only kids data (3 sample per subject, 20 > subjects)? I definitely do not dispute the need to have both adult and paediatric data in the analysis (so I agree :-) ). I see two reasons for this (perhaps more if I took more time). The first and most important reason is combining adult and paediatric data together is a great (only) way to learn how children differ pharmacokinetically from adults and how doses can be scaled to achieve equivalent exposures. Secondly, especially in this case, it is often helpful to combine data sets together to improve the informativeness of the overall design. This latter point, however was the point of my previous email. Some care must be taken to assess the accuracy of covariate effects given the unbalanced nature of the design. > While optimal design can be used to extract more > information from the same number of samples, it is not a > substitute for the real data. Even with optimal design of the > pediatric study (with the same 20 subjects, 3 optimal sample > points) I bet you would gain by using adult data as well. You always gain by summing over data (unless the new data is negatively informative which is unlikely in any PK situation). So I don't exactly follow your point. The question to me is simply, what chance do I have of identifying a model that allows me to draw appropriately accurate conclusions. Optimal design is a way that allows investigators to improve the informativeness of data. Obviously, no data = no information. Steve -- Professor Stephen Duffull Chair of Clinical Pharmacy School of Pharmacy University of Otago PO Box 913 Dunedin New Zealand E: [EMAIL PROTECTED] P: +64 3 479 5044 F: +64 3 479 7034 Design software: www.winpopt.com