RE: PD initialization

From: "Piotrovskij, Vladimir [JanBe]" <VPIOTROV@janbe.jnj.com> Subject: RE: PD initialization Date: Mon, 9 Oct 2000 11:25:36 +0200 The control and the simulated data set below illustrate my point. It works perfectly in the estimation mode. It is a single-individual example which can easily be generalized for the population case. Unexpectedly, the situation turned out to be not so simple. When the control below is run in a simulation mode it produces biased PRED at TIME = 0 for both compartments 1 and 2. Nevertheless, if OMEGAs are fixed to 0 there is no bias in PRED anymore. It seems to be a bug. I will explore this further and will post a question to nmconsult. Best regards, Vladimir ---------------------------------------------------------------------- NM-TRAN Control stream $PROBLEM PK-PD simultaneous $INPUT ID TIME DV AMT CMT $DATA nmd.ssc $SUB ADVAN9 TOL=6 $MODEL COMP=(CENTRAL) COMP=(EFFECT) $PK K = THETA(1) EC50 = THETA(2) K0 = THETA(3) KE = THETA(4) S1 = THETA(5) F2 = K0/KE $DES DADT(1)=-K*A(1) ; PK CP = A(1)/S1 EFF = 1-CP/(CP+EC50) DADT(2)= K0*EFF - KE*A(2) ; PD $ERROR IF (CMT.EQ.1) THEN Y = F * EXP(ERR(1)) ELSE Y = F * EXP(ERR(2)) ENDIF $THETA (0 0.5 1); 1 K (0 0.5 2); 2 EC50 (0 1.0 5); 3 K0 (0 0.1 1); 4 KE (0 20.0 100); 5 S1 $OMEGA .02 .05 ;$SIM (51813) $EST PRINT=10 MAX=9990 $COV $TABLE ID TIME AMT CMT FILE=tab.ssc NOPRINT ONEHEADER Data set 1 0 0 100 1 1 0 0 1 2 1 0 4.74 0 1 1 0 11.04 0 2 1 1 3.0668 0 1 1 1 8.5346 0 2 1 2 1.9344 0 1 1 2 6.6172 0 2 1 3 1.0375 0 1 1 3 9.0932 0 2 1 4 0.56123 0 1 1 4 9.3156 0 2 1 5 0.44249 0 1 1 5 7.8811 0 2 1 6 0.21302 0 1 1 6 5.78 0 2 1 7 0.15583 0 1 1 7 7.0446 0 2 1 8 0.083318 0 1 1 8 7.7035 0 2 1 9 0.047182 0 1 1 9 5.8446 0 2 1 10 0.033686 0 1 1 10 7.3329 0 2