NONMEM 7.4.3 is the most up-to-date in usage of NPDE on BLQ records.

Robert J. Bauer, Ph.D.
Senior Director
Pharmacometrics R&D
ICON Early Phase
820 W. Diamond Avenue
Suite 100
Gaithersburg, MD 20878
Office: (215) 616-6428
Mobile: (925) 286-0769
[email protected]<mailto:[email protected]>
www.iconplc.com<http://www.iconplc.com/>

From: [email protected] [mailto:[email protected]] On 
Behalf Of STANDING, Joseph (GREAT ORMOND STREET HOSPITAL FOR CHILDREN NHS 
FOUNDATION TRUST)
Sent: Monday, February 25, 2019 1:32 AM
To: Smit, Cornelis (Klinische Farmacie); [email protected]
Subject: RE: [NMusers] Strange PRED prediction in SAEM with M3 BQL handling

Dear Cornelis,

Please have a look at the following for how to visualise NPDEs with a "PRED" 
for BLQ data:

Nguyen THT, Comets E. Mentre ́ F. Extension of NPDE for evaluation of nonlinear 
mixed
effect models in presence of data below the quantification limit with 
applications to HIV
dynamic model. J Pharmacokinet Pharmacodyn (2012) 39:499–518

This is possible to implement in NONMEM as per the 7.4 userguide NPDE section 
for the code.

BW,

Joe



Joseph F Standing
MRC Fellow, UCL Institute of Child Health
Antimicrobial Pharmacist, Great Ormond Street Hospital
Honorary Senior Lecturer, St George's University of London
Tel: +44(0)207 905 2370
Mobile: +44(0)7970 572435
________________________________________
From: [email protected] [[email protected]] on behalf of 
Smit, Cornelis (Klinische Farmacie) [[email protected]]
Sent: 22 February 2019 10:11
To: [email protected]
Subject: RE: [NMusers] Strange PRED prediction in SAEM with M3 BQL handling

Hi Andrew,

When your observation is <BLQ, M3 gives you a likelihood of this value being < 
BLQ in the PRED column. So this value will be close to 1 when the model is 
fairly sure that the concentration should be BLQ. This might explain why the 
PREDs might be relatively high in your diagnostics here. I usually exlude the 
<BLQ values in my GOF diagnostics, and check for model misspecification with a 
VPC showing BLQ data (as described in 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2691472/<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2691472/>
 ). You can do this with the old xpose package. I don’t think there is any way 
to visualize the BLQ prediction in the ‘usual’ GOF but I’m very curious if 
someone else has some ideas regarding this.

Kind regards,

Cornelis Smit
Hospital Pharmacist / PhD candidate

Dept. of Clinical Pharmacy
St. Antonius Hospital

Dept. of Pharmacology,
Leiden Academic Centre for Drug Research,
Leiden University, Leiden, The Netherlands

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Van: [email protected] [mailto:[email protected]] Namens 
Andrew Tse
Verzonden: vrijdag 22 februari 2019 10:23
Aan: [email protected]
Onderwerp: [NMusers] Strange PRED prediction in SAEM with M3 BQL handling

Dear all,

I am running SAEM with M3 BQL handling method via PsN but having some strange 
PRED values in mytab table if someone can shed some light:
I have tried using FOCE (excluding BQL data) & SAEM (excluding BQL data) both 
have normal looking fitting with data in individual plots.
Once I have coded SAEM with M3 codes and include BQL data it showed very 
strange PRED vs time plots (eg. 100 times over prediction at BQL time point). 
IPRED had normal results.

Here are the control stream that I have used:
$PK
TVCL=THETA(1)
MU_1=LOG(TVCL)
CL=EXP(MU_1+ETA(1))

TVV2=THETA(2)
MU_2=LOG(TVV2)
V2=EXP(MU_2+ETA(2))

TVQ=THETA(3)
MU_3=LOG(TVQ)
Q=EXP(MU_3+ETA(3))

TVV3=THETA(4)
MU_4=LOG(TVV3)
V3=EXP(MU_4+ETA(4))

K23=Q/V2 ;Distribution rate constant
K32=Q/V3 ;Distribution rate constant
KA=0

A_0(1)=0
A_0(2)=0
A_0(3)=0

$DES
DADT(1)= -KA*A(1)
DADT(2)= -CL*A(2)/V2-K23*A(2)+K32*A(3)
DADT(3)= K23*A(2)-K32*A(3)


$ERROR

IPRED=A(2)/V2
W=SQRT(THETA(5)**2+((THETA(6)*IPRED)**2))

IF (LIMI.EQ.1) LIM= 0.05 ;BATCH 1
IF (LIMI.EQ.2) LIM= 0.01 ;BATCH 2
IF (LIMI.EQ.3) LIM= 0.025 ;BATCH 3

IF(BQL.EQ.0) THEN
F_FLAG=0
Y=IPRED+W*ERR(1)
ELSE
F_FLAG=1 ;BQL so Y is likelihood
Y=PHI((LIM-IPRED)/W)
ENDIF
IWRES=(DV-IPRED)/W
IRES=DV-IPRED

My question is that whether there is error in my M3 $ERROR model? or whether 
PRED values for BQL means something else other than prediction for BQL data?

Thanks a lot.

Kind regards,
Andrew Tse

Research Pharmacist


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  • ... Andrew Tse
    • ... Smit, Cornelis (Klinische Farmacie)
      • ... Tingjie Guo
      • ... Leonid Gibiansky
      • ... STANDING, Joseph (GREAT ORMOND STREET HOSPITAL FOR CHILDREN NHS FOUNDATION TRUST)
        • ... Bauer, Robert
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