Hi Dongfen,
Do you have IPRED computed correctly? Then there could be an error
during the PRED compute. Do you have NOABORT on EST step? You can try to
use NOHABORT and see what happen, or use $ABBREV PROTECT (in case this
would mask the error of PRED computations).
Another option is to get PRED from IPRED, see manual, like:
PREDU=1
If(COMACT==1) PREDU=IPRED
$TABLE ... PREDU ...
If PREDU=1 in the table, then there was an error on the step that
computes PRED values. If PREDU is reasonable but PRED is still 0, then
the problem is somewhere else.
You may also try FNLETA=0 (thus avoiding recompute of ETAs on the table
step): not sure whether it can help, but it is easy to try.
ADVAN13 is more stable than ADVAN6, so if you are using 6, you may try 13.
It looks like a numerical issue so anything that changes numerical
computations is worthwhile to try (NSIG, SIGL, TOL, etc.)
Also, check the .lst file and the dos windows in case of helpful error
messages.
Regards,
Leonid
On 2/22/2025 7:07 PM, Yuan, Dongfen [JRDUS] wrote:
Hello,
I am using an existing model to describe new study data. The covariate
model needs to be updated. The model is quite complicated: time-varying
PK and many IIVs. It takes a long time to converge. I want to remove
some of the IIVs to shorten the run time for covariate search.
Unexpectedly, after removing the IIV (one at a time), PRED=0 for all
records. I got the same issue for multiple IIVs. It's a proportional
residual model on the original scale, IPRED was fine, so dose was given.
The model converged and parameter estimates were close to values before
removal, so it didn't seem like an estimation issue. Before removal,
PRED was fine and not a small number, so it couldn't be a digit issue (I
also tried to change format for $Table but it did not work).
I am having a hard time understanding why. Apology that I cannot post
the full control stream here. It's NONMEM 7.5 and intel fortran. Hope
you can point me to the right direction. Really appreciate your guidance!
Thank you,
Dongfen
