RE: How sparse is too sparse?

From: "Kowalski, Ken" Ken.Kowalski@pfizer.com Subject: RE: [NMusers] How sparse is too sparse? Date: Thu, June 10, 2004 3:51 pm Robert, As Leonid indicates, you won't be able to partition out inter-occasion variability with only 1 sample per occasion per subject. I agree with Leonid that you should analyze it using a pop PK model rather than to perform naive pooling. Also, you should point out the limitations of the design and clarify expectations with regards to estimating Tmax, Cmax, t1/2, and AUC. With such sparse sampling and depending on the timing of the samples I suspect that you will get a lot of shrinkage (bias towards the mean) in the empirical Bayes predictions for some of these parameters. At best you might be able to get a good population estimate of CL/F and its IIV from which you can provide information on AUC. Depending on the timing and underlying true model (e.g., 2-comp vs 1-comp) your sparse design may not provide reliable estimates of Tmax, Cmax and t1/2. Ken