Changing number of observations per indivdual record.
From: "David Nix, Pharm D." <nix@pharmacy.arizona.edu>
Subject: Changing number of observations per indivdual record.
Date: Mon, 14 May 2001 15:55:48 -0700
The installation guide (Chapter III, page 20) provides information about increasing the number of observations per individual record. The line "PARAMETER (NO=50)" needs to be changed in CELS, ELS, INITL, INPT, NCONTR, OBJ, OBJ2, OS PRRES, ROOT, and SIML subroutines. However, I was unable to locate the above line in any of the *.for files listed about in the nm subdirectory. Am I looking in the wrong place? I would appreciate any guidance here.
I have seen this discussion going on in the recent past. The data involved administration of the same drug 4 times separated by 2 weeks washout. Results of the population analysis are considerably different, primarily due to the Tlag estimate. Tlag in the population analysis appears quite short and this leads to a low ka and slower CL compared to individual modeling results. The individual fits (from nonlinear regression) look very good - this leads me to think that the population estimates need to be improved.
One issue is that I deleted all "0.0" concentations even if they were before the first detectable concentration. These concentrations could provide additional help for determining Tlag. The problem is the limit on the number of data points per individual. I have up to 18 samples per individual x 4 treatments = 72.
Best estimates for nonlinear regression modeling based on 1 compt, 1st order input and 1st order elim.
Tx ka V ke Tlag CL
1 0.988 (73.1) 1271 (65.9) 0.159 (67.5) 2.342 (64) 201
2 1.071 (124.6) 845 (88.2) 0.133 (79.7) 1.672 (83.6) 112
3 1.915 (116.3) 1273 (51.9) 0.17 (118.8) 2.135 (75) 216
4 0.807 (68.8) 1358 (46.7) 0.174 (179.7) 1.457 (67.2) 236
F values: Tx 1 = 1.00 Tx 2 = 1.80 Tx 3 = 0.93 Tx 4 = 0.85
Estimates from population analysis (same model, param as ka, V, CL, Tlag)
0.363 (47.5) 1470(45.9) ~0.0477 0.494(48.9) 70.1(17.9)
F values: Tx 1 = 1.00 Tx 2 = 2.32 Tx 3 = 1.04 Tx 4 = 0.982