Hello
I would like to model inter-study variability on the of the inter-subject
variability with NONMEM 74
A subject belongs to a study, therefore those two random effects are nested
Following the instruction, I code as below, where ETA8 is at the subject level
and ETA9 is at the study (STUD) level.
$INPUT ID STUD TIME TIM2 TAD NT CMT EVID MDV BLOQ AMT DOSE RATE LIDV=DV
LNDV WT0 TRT1S TRT2S PAS0
...
$PK
...
TVF1 = THETA(8) + ETA(8) + ETA(9)
F1 = (EXP(TVF1)/(1+EXP(TVF1)))
...
$LEVEL STUD=(9[8])
The fit with NONMEM 743 (fortran compliler) seems correct and the estimates for
the variance (OMEGA) of ETA8 and for ETA9 are provided.
But when looking at the ETA9 values (the empirical bayes estimates), I notice
that
(1) Different subjects of the same study have different ETA9 values, while I
would expect that all subjects of a study have same ETA9 value
(2) The ETA9 value is proportional to the ETA8 value (ie, plotting ETA8
versus ETA9 from all subjects of all studiers results in all points on the same
diagonal line)
Am I coding incorrectly ?
Any help would be more than welcome
Many thanks
Thomas Dumortier
Thomas Dumortier
Director Pharmacometrics
Novartis Pharma AG
Postfach
CH-4002 Basel
SWITZERLAND
Phone +41 61 3240946
Fax +41 61 3241246
thomas.dumort...@novartis.com<mailto:thomas.dumort...@novartis.com>
