RE: Incorporating duplicate assays

From: "Piotrovskij, Vladimir [PRDBE]" VPIOTROV@PRDBE.jnj.com Subject: RE: [NMusers] Incorporating duplicate assays Date: Wed, 16 Nov 2005 21:09:29 +0100 Paul, Besides the assay variability the residual error includes imprecision in dosing and sampling times, and model misspecification error. If you use raw data with multiple measurements per time point you have to modify the residual error structure. The concept of nested random effects may suite. Below is an example of the $ERROR block that you can try: ; REPEATED OBS OBS1 = 0 OBS2 = 0 OBS3 = 0 IF(OBSN.EQ.1) OBS1=1 IF(OBSN.EQ.2) OBS2=1 IF(OBSN.EQ.3) OBS3=1 ASSERR = OBS1*ERR(1) + OBS2*ERR(2) + OBS3*ERR(3) Y = F * (1 + ASSERR + ERR(4)) ..... $SIGMA BLOCK(1) .1 $SIGMA BLOCK(1) SAME $SIGMA BLOCK(1) SAME $SIGMA .2 Best regards, Vladimir ----------------------------------------------------------------- Vladimir Piotrovsky, Ph.D. Research Fellow, Advanced PK-PD Modeling & Simulation Clinical Pharmacology and Experimental Medicine Johnson & Johnson Pharmaceutical Research & Development B-2340 Beerse Belgium