Two dependent variables

3 messages 3 people Latest: Jan 31, 2007

RE: Two dependent variables

From: Stephen Duffull Date: January 30, 2007 technical
Hi > Hello, > I was wondering if I could model two DVs simultaneously with > the same control stream. > Like have to equations A=(equation) > B= (equation) > > I have data for two different drugs from same patients Could > I do it nomem ? This is somewhat of a large question. Quite simply: yes you can model several drugs simultaneously in NONMEM. If they have the same structural model (e.g. both 2 cpt) then this makes life simpler, but otherwise using the ODE solver ADVANs (6, 9) or the linear algebra solutions (ADVANs 5, 7) you can pretty much do anything you like... Our group has modelled 5 linked drugs simultaneously in NONMEM - I can't see that there's a limit other than on runtimes :-) Cheers Steve -- Professor Stephen Duffull Chair of Clinical Pharmacy School of Pharmacy University of Otago PO Box 913 Dunedin New Zealand E: stephen.duffull P: +64 3 479 5044 F: +64 3 479 7034 Design software: www.winpopt.com
Quoted reply history
> -----Original Message----- > From: owner-nmusers > [mailto:owner-nmusers > Sent: Wednesday, 31 January 2007 7:41 a.m. > To: nmusers > Subject: [NMusers] Two dependent variables > > Hello, > I was wondering if I could model two DVs simultaneously with > the same control stream. > Like have to equations A=(equation) > B= (equation) > > I have data for two different drugs from same patients Could > I do it nomem ? and if yes how do I do it? > > Any help is appreciated, > Thanks > >

Re: Two dependent variables

From: Zheng Lu Date: January 31, 2007 technical
Dear all: As to this kind of situation(at least two types of observations or same type of observations from at least two different assay), DO we need change our default objective function? Because I am thinking we will estimate our parameters based on multivariate normal distribution(at least bivariate normal distribution) instead of univariate normal distribution(only one type of observation), so we will have different variance across the observations and we will have covariance issue which is not zero. thanks a lot. Zheng Lu sixth-year graduate student/Smith Lab Department of pharmaceutical sciences College of Pharmacy University of Michigan 428 Church Street, Ann Arbor, MI 48109-1065 Tel: 734-763-7608(o), 734-647-1427(o), 734-647-1437(L) Fax: 734-615-6162(o), 734-763-3438(o) Quoting Nick Holford <n.holford > Hi, > > The 'FLAG' method is a trick that only works with 2 DVs. It is also a > bit inefficient because it requires that both the PK and PD > prediction are calculated but only one is used. > > A more general method uses IF THEN blocks e.g. if you have a data > item DVID with the value 1 with a conc observation and the value 2 > with an effect observation of one type and value of 3 with an effect > observation of a different type: > > CONC=F > IF (DVID.EQ.1) THEN > Y=CONC + ERR(1) > ENDIF > IF (DVID.EQ.2) THEN > Y=EMAX2*CONC/(EC502+CONC) + ERR(2) > ENDIF > IF (DVID.EQ.3) THEN > Y=EMAX3*CONC/(EC503+CONC) + ERR(2) > ENDIF > > Nick > >> >> Yes, you could do a simultaneous fitting with the same >> control stream in NM. For example you could >> have a dummy variable (Flag) that tells NM which likelihood >> function goes with which data. See below >> >> >> >> Flag 0 = PK, Flag 1=PD >> >> >> >> $ERROR >> >> Y=CONC*(1-Flag) + EFF* Flag >> >> >> >> Hopefully this would help. >> >> >> >> Best, >> >> Nidal AL-Huniti, PhD >> >> >> On 1/30/07, navin goyal <navin1180 >> >> Hello, >> I was wondering if I could model two DVs simultaneously >> with the same control stream. >> Like have to equations A=(equation) >> B= (equation) >> >> I have data for two different drugs from same patients >> Could I do it nomem ? and if yes how do I do it? >> >> Any help is appreciated, >> Thanks >> >> >> >> >> > > > > -- > Nick Holford, Dept Pharmacology & Clinical Pharmacology > University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand > email:n.holford > http://www.health.auckland.ac.nz/pharmacology/staff/nholford/ > > >

RE: Two dependent variables

From: Serge Guzy Date: January 31, 2007 technical
If we assume that the residual variances (sigma) across the different responses are independent, then the computation of the objective function is similar than the one obtained with one response. There is no need to change what you call the default objective function. Serge Guzy
Quoted reply history
-----Original Message----- From: owner-nmusers On Behalf Of Zheng Lu Sent: Wednesday, January 31, 2007 9:11 AM To: Nick Holford Cc: nmusers Subject: Re: [NMusers] Two dependent variables Dear all: As to this kind of situation(at least two types of observations or same type of observations from at least two different assay), DO we need change our default objective function? Because I am thinking we will estimate our parameters based on multivariate normal distribution(at least bivariate normal distribution) instead of univariate normal distribution(only one type of observation), so we will have different variance across the observations and we will have covariance issue which is not zero. thanks a lot. Zheng Lu sixth-year graduate student/Smith Lab Department of pharmaceutical sciences College of Pharmacy University of Michigan 428 Church Street, Ann Arbor, MI 48109-1065 Tel: 734-763-7608(o), 734-647-1427(o), 734-647-1437(L) Fax: 734-615-6162(o), 734-763-3438(o) Quoting Nick Holford <n.holford > Hi, > > The 'FLAG' method is a trick that only works with 2 DVs. It is also a > bit inefficient because it requires that both the PK and PD prediction > are calculated but only one is used. > > A more general method uses IF THEN blocks e.g. if you have a data item > DVID with the value 1 with a conc observation and the value 2 with an > effect observation of one type and value of 3 with an effect > observation of a different type: > > CONC=F > IF (DVID.EQ.1) THEN > Y=CONC + ERR(1) > ENDIF > IF (DVID.EQ.2) THEN > Y=EMAX2*CONC/(EC502+CONC) + ERR(2) > ENDIF > IF (DVID.EQ.3) THEN > Y=EMAX3*CONC/(EC503+CONC) + ERR(2) > ENDIF > > Nick > >> >> Yes, you could do a simultaneous fitting with the same control >> stream in NM. For example you could >> have a dummy variable (Flag) that tells NM which likelihood >> function goes with which data. See below >> >> >> >> Flag 0 = PK, Flag 1=PD >> >> >> >> $ERROR >> >> Y=CONC*(1-Flag) + EFF* Flag >> >> >> >> Hopefully this would help. >> >> >> >> Best, >> >> Nidal AL-Huniti, PhD >> >> >> On 1/30/07, navin goyal <navin1180 >> >> Hello, >> I was wondering if I could model two DVs simultaneously >> with the same control stream. >> Like have to equations A=(equation) >> B= (equation) >> >> I have data for two different drugs from same patients >> Could I do it nomem ? and if yes how do I do it? >> >> Any help is appreciated, >> Thanks >> >> >> >> >> > > > > -- > Nick Holford, Dept Pharmacology & Clinical Pharmacology University of > Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand > email:n.holford > http://www.health.auckland.ac.nz/pharmacology/staff/nholford/ > > > -- The information contained in this email message may contain confidential or legally privileged information and is intended solely for the use of the named recipient(s). No confidentiality or privilege is waived or lost by any transmission error. If the reader of this message is not the intended recipient, please immediately delete the e-mail and all copies of it from your system, destroy any hard copies of it and notify the sender either by telephone or return e-mail. Any direct or indirect use, disclosure, distribution, printing, or copying of any part of this message is prohibited. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of XOMA.