Re: Generating TAD with ADDL dosing format
Hi Camila,
It sounds like you've got two questions here-- one related to NONMEM and one related to the other program you're using to create your VPC. The NONMEM question appears to be "How do I get TAD in my data without changing my dataset?" The second question appears to be "How to I stratify my VPC based on that new TAD variable instead of TIME?"
For the second question, what program are you using for VPC?
For the first question, others may have a more elegant answer, but I think that you're right: ADDL makes many dose-related events difficult. The simplest answer is to revise your dataset adding a TAD column. If you can't do that, then something like this will work assuming that you only have one dosing record per subject. (Note that the code below was typed directly into email, so it may have typos.)
; Set TAD to -1 before any dose record for the subject
IF (NEWIND.EQ.2) THEN
DOSETIME = -1
ADDLREC = 0
IIREC = 0
ENDIF
; Capture the (most recent) dosing information for this subject
IF (EVID.EQ.1 .OR. EVID.EQ.4) THEN
DOSETIME = TIME
ADDLREC = ADDL
IIREC = II
ENDIF
; Calculate TAD from the single dose record for a subject in the data set assuming ; that there is only one dose record per subject or that the dose records occur ; such that the most recent dose record is the only one important for calculating ; TAD for a subject. This assumption would not hold if there is a dose record ; with ADDL that has a dose record for a time in the middle of those ADDL doses.
IF (DOSETIME.LT.0) THEN
; This subject has not received a dose yet, set TAD to -1
TAD = -1
ELSEIF ((TIME-DOSETIME) .LE. ((ADDLREC+1)*IIREC)) THEN
; This subject is in the middle of the ADDL records for this dose,
; calculate time since most recent dose.
TAD = (TIME-DOSETIME) - INT((TIME-DOSETIME)/IIREC)*IIREC
ELSE
; This subject is are after the last ADDL dose, calculate time since the final
; dose (observed so far).
TAD = (TIME-DOSETIME) - ((ADDLREC+1)*IIREC)
ENDIF
Thanks,
Bill
Quoted reply history
On 12/20/2016 6:45 AM, de Almeida, Camila wrote:
> Hello,
>
> I was wondering if I could get some guidance from this great group. My issue is primarily with some diagnostic analysis, but this is taking me back to an old NONMEM problem.
>
> My aim is to run a VPC on a model I implemented, and if possible change the idv to TAD instead of TIME. The reason for that is the VPC graph based on TIME looks dreadful as the data is sparse and from different studies of different lengths.
>
> I’m having issues generating the TAD output column from my NONMEM run. I naively assumed I could easily do that, but looking at the NONMEM archives it seems this gets tricky when your dosing events are written using ADDL. Has anyone ever managed to find a solution for this? And if not, is there an alternative way to run the VCP on TAD, do we really need to get this column from NONMEM’s output?
>
> Thanks all,
>
> *Camila de Almeida, PhD*
>
> PKPD Scientist,
>
> *Modelling & Simulation, IMED Oncology DMPK*
>
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Human Predictions Logo < http://www.humanpredictions.com >*William S. Denney, PhD*
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