Re: [NMusers] Log transformation of imputed BQL

From: Dennis Fisher <fisher_at_plessthan.com>
Date: Wed, 27 Jul 2016 14:25:33 -0700

one thing that you could do is multiply all the values by 1000 (i.e., =
change the units)

Dennis Fisher MD
P < (The "P Less Than" Company)
Phone / Fax: 1-866-PLessThan (1-866-753-7784)
www.PLessThan.com <http://www.plessthan.com/>




> On Jul 27, 2016, at 11:11 AM, Bharadwaj, Manushree =
<manushb_at_ostatemail.okstate.edu> wrote:
>
> Dear friends,
>
> I log transformed the plasma concentrations in my data and I am using =
this log transformed data as my dependent variable (DV). I imputed the =
BQLs to LLOQ/2, which is my case is (1/2=0.5). The natural log of 0.5 =
is negative which mean that I have negative values in my DV column.
> While the parameter estimates look somewhat reliable, I have negative =
points plotted in the diagnostic plots such as DV vs PRED, DV and PRED =
vs TIME, etc.
> My questions are-
> 1. What is the best way of dealing with <1 DV/plasma concentration =
values while transforming into natural logarithm?
> 2. In my situation discussed above, where I have negative DV values in =
my data, has the NONMEM ignored or considered the negative numbers when =
estimating the parameter values?
>
> Thank you,
> Manu
>
> --
> With regards-
> Manushree Bharadwaj, BVSc, PhD Candidate
> Graduate Teaching Associate
> Department of Physiological Sciences
> Center for Veterinary Health Sciences
> Oklahoma State University
> Stillwater, OK-74074


Received on Wed Jul 27 2016 - 17:25:33 EDT

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