From:"Luciane Velasque"
Subject:[NMusers] large CV
Date:Tue, 5 Mar 2002 10:25:56 -0300
Hi !
I am modeling the population pharmacokinetics of didanosine. I have 72 voluntaries
who took one oral dose of 200 mg. Thirteen blood samples were obtained
in the times 0, 0.25, 0.5, 0.75, 1.0, 1.5, 2, 2.5, 3, 4, 6, 8 e 10 .
the CONTROL STATEMENTS is : ......
$SUBROUTINES ADVAN4 TRANS4
$PK
TVCL=THETA(1)
CL=TVCL*EXP(ETA(1))
TV2=THETA(2)
V2=TV2+ETA(2)
TVQ=THETA(3)
Q=TVQ*EXP(ETA(3))
TVV3=THETA(4)
V3=TVV3*EXP(ETA(4))
TKA=THETA(5)
KA=TVKA*EXP(ETA(5))
S2=V2
S3=V3
K=CL/V2
K23=Q/V2
K32=Q/V3
KA=KA
$ERROR
Y = F + F*ERR(1)
$THETA (0,120)(0,5)(0,30)(0,50)
$OMEGA 1 1 1 1
$SIGMA 1
$ESTIMATION MAXEVAL=9999 SIGDIGITS=2 POSTHOC
$COVARIANCE
The estimated OMEGA(V2) is very large and the CV = SQRT(OMEGA(V2))*100 = 1600 %.
Why is this happening ?
Thanks in advance.
Luciane
large CV
From:"Luciane Velasque"
Subject: Re: [NMusers] large CV
Date: Tue, 5 Mar 2002 12:21:02 -0300
When I use FOCE I obtain the message :
0MINIMIZATION SUCCESSFUL
NO. OF FUNCTION EVALUATIONS USED: 360
NO. OF SIG. DIGITS IN FINAL EST.: 2.3
ETABAR IS THE ARITHMETIC MEAN OF THE ETA-ESTIMATES,
AND THE P-VALUE IS GIVEN FOR THE NULL HYPOTHESIS THAT THE TRUE MEAN IS 0.
ETABAR: -.18E-03 .14E-05 -.26E-07 -.46E-06 .87E-03
P VAL.: .10E+01 .94E+00 .72E+00 .80E+00 .92E+00
0R MATRIX ALGORITHMICALLY NON-POSITIVE-SEMIDEFINITE
BUT NONSINGULAR
0COVARIANCE STEP ABORTED
What should make ?
thanks
P.S. In the Statment Control
V2= TV2*EXP(ETA2)