Re: Log transformation of imputed BQL
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/
Quoted reply history
> On Jul 27, 2016, at 11:11 AM, Bharadwaj, Manushree
> <[email protected]> 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