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Dr Jeliffe will love this one. We are now asked to report assay
perfromance in terms of total error (TE) which is Cv + absolute value
of the Bias. This will ceratinly obscure the precision and the
actual bias as well. As I suggested before including the CV with
the mean does not obscure the SD but since Cv=Sd/mean the Sd can be
calculated. TE does though make things a little more obscure
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The following message was posted to: PharmPK
Dear Dr. O'Connor:
You are right. It is a zinger! Why do they do this? It does not
seem to be science in any form at all. I wish SO MUCH that they would
simply try to learn a little statistics about the credibility of data
points such as Fisher information to aid them in what they do. They
make themselves appear very foolish when they do these things year
after year in such blind ways, without ever trying to learn what the
statisticians are saying about errors.
In addition, what is the use of reporting measurements in molar
units when the doses are given in weight units? It is not real
science, and it is an additional obstacle that everyone alse has to
go through in order to get a correct estimate of the apparent volume
of distribution. If doses were similarly given in molar units, there
would be no problem, Neither one is any more "scientific" than the
other, in my view. The real question is what is useful to the people
who ordered the lab test in the beginning.Why doesn't the lab try to
help them instetad of acting so superior to everyone, when they re
really being quite foolish and showing it to everybody?
It seems to me that the labs, by such behavior, are definitely
interfering with the ability to use their results. Again, if I were
in the ministry of health, or a patient, I would be really angry if a
report were given in such a poor way when it is so easy to do it
correctly, and I would not want to pay for it. Why should I? What has
a result below the LOQ done for me as a patient? Nothing, It is
simply the lab playing with itself. Same with reporting units which
are in units different from those in which the doses are given. Why
don't they discuss some of these ideas with clinicians and especially
with staticians before they blindly go ahead and do these things? Not
very smart!
Puzzled and disappointed,
Roger Jelliffe
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The additional battle I am trying to fight is even worse. Choosing
to ignore the statement in the guidance and elsewhere that stability
samples should be run against fresh (day of use) standards and
controls many scientists argue that since all the samples are frozen
it is not necessary to run fresh materials. Also, they argue that
preparing fresh materials adds to the variability of the assay and
that to control for this they wish to prepare very large batches of
controls and standards, Freeze them and use them throughout
validation and sample analysis.
My argument has been that the samples were originally fresh, that TX,
PK and PD events are related to concentrations in fresh material not
frozen, and that it is prudent and scientifically sound to establish
most of the parameters for validation in fresh materials, then
demonstrate either that there is no difference after freezing or
demonstrating that there is a difference, then explore and address
the difference. Not to mention the fact that frozen QC and
standards can decline at the same rate and without a good comparator,
we would be oblivious to the change. Until a new batch is needed.
The logic of not doing this comparison escapes me but that is where
most folks are going. I can suggest the other but I have been
losing this one with alarming frequency.
On the TE front perhaps you should address the folks-- the next
opportunity may be at the National Biotech council in San Diego this
June. It is the large molecule component of the AAPS meetings.
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)