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