Re: Missing Gender (Categorical values)

From:Nick Holford Subject:Re: [NMusers] Missing Gender (Categorical values) Date:Wed, 31 Jul 2002 08:58:57 +1200 Alan, I thought the idea was to simulate SEX in order to help discover the effect of SEX on other model parameters. Can you be be clearer about what you mean about taking this into account BEFORE doing the imputation? The original Rubin paper on imputation is Rubin DB, Schenker N. Multiple imputation in health-care databases: an overview and some applications. Stat Med 1991;10(4):585-98. Joe Shafer ( http://www.stat.psu.edu/~jls/) gave an excellent talk at PAGE in 2001 on the topic and has lots of stuff on his web pages. I am not aware of any applications of multiple imputation using NONMEM but Lewis Sheiner has remarked that there is little point because you can always do joint modelling which is a better overall approach. You can look at Mould DR, Holford NHG, Schellens JHM, Beijnen JH, Hutson PR, Rosing H, et al. Population Pharmacokinetic and Adverse Event Analysis of Topotecan in Patients with Solid Tumors. Clinical Pharmacology & Therapeutics 2002;71(5):334-348 for a recent application of the joint modelling approach for missing covariates. The initial suggestion for using this with NONMEM was Karlsson M, Jonsson E, Wiltse C, Wade J. Assumption testing in population pharmacokinetic models: illustrated with an analysis of moxonidine data from congestive heart failure patients. J Pharmacokinet Biopharm 1998;26(2):207-46. -- Nick Holford, Divn Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x6730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/