RE: [NMusers] Modeling concentration data with imprecise sampling time

[Mark Sale - Next Level Solutions]

Maybe I'm missing something, but would it work to say that the infusion start time is imprecise instead? For example, if the infusion starts at 0, and the sample is supposed to be at 1, move everything back 0.5 hours, give the dose at 0, with a 0.5 hr lag time, then the sample at 1.5 TIME AMT  DV  RATE   0       100   .     100  ; infusion is lagged - estimated infusion lag time, initial 0.5 hours 1.5      .     .        .   ; observation recorded as 1 hr, will be 1 hour after infusion is ALAG1 is 0.5 $PK ALAG1 = THETA(1) $THETA (0,0.5) But, probably everything else would need to be off by the ALAG1 time as well. If that isn't the case (e.g., other samples are timed correctly), you could do the admittedly strange double model, with one infusion into one pk model, but only predicts that first (1 hr) observation), and all the rest based on a completely different observation. TIME AMT  DV  RATE   CMT 0       100   .     100      1 0       100   .     100      2 1.5      .     .        .       1  ; this is the observation, recorded at 1 hour, but is at unknown time 2         .     .        .       2  ; this is the observation, recorded at 2 hours, and really is 3         .     .        .       2  ; this is the observation, recorded at 3 hours, and really is $PK ALAG1 = THETA(1) ALAG2 = 0 K10 = THETA(2) K20 = THETA(2) Mark Sale MD President, Next Level Solutions, LLC www.NextLevelSolns.com 919-846-9185 A carbon-neutral company See our real time solar energy production at: http://enlighten.enphaseenergy.com/public/systems/aSDz2458 -------- Original Message -------- Subject: [NMusers] Modeling concentration data with imprecise sampling time From: mdkz...@aol.com Date: Thu, June 02, 2011 11:44 am To: nmusers@globomaxnm.com All:      I have a data set following a constant rate 1-hour infusion where the time of 1-hour sample is imprecise.  In some cases the "1-hr" sample was taken prior to infusion termination as it was intended; however, in others it was quite apparently take after the infusion ended.  I'm thinking of modeling with the time of the "1-hr" sample as a "theta".  Does anyone have a NONMEM coding example showing how to do this?  Any other suggestions as to how to handle this would be appreciated as well. Thanks,  Michael