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The following message was posted to: PharmPK
I have a question regarding accuracy and precision of sample analysis
supporting PK. In most instrumental methods precision and accuracy has a
greater probability of meeting very high tolerances. This probability is
increased if there are few processing steps and can be improved even
more so with internal standards. In ligand binding assays high
tolerances may not be met because of the complexity of processing and
the dynamic vs static nature of responses in binding assays.
1)Are there a priori limits for data coming from ligand binding assays?
2)Are they to be held to the same high tolerances as instrumental? 3)
What tolerances would be considered too high?
Thank you
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The following message was posted to: PharmPK
The answer is in the FDA bioanalytic guidance.
A priori guidance on limits for precision and accuracy are the same as
for chemical assays.
The basis for this decision was as follows: (not in order of criteria
used)
1) To have consistent standards with the EU.
The EU had a meeting to address this issue around the time FDA was
discussing it. They recommended the same limits for ligand binding
assays as for chemical assays.
2) Expert opinion from several experts was that using the same criteria
was achievable and was not onerous.
3) Review of submitted data across a number of ligand assays for various
drugs suggested that precision and accuracy well within the guidance
limits could routinely be achieved with ligand binding assays.
4) Limits should not be so wide that valid pharmacokinetic estimates and
resultant clinical decisions cannot be made.
5) The guidance limits are a guidance, exceptions are always looked at
on a case by case basis.
Ron Kavanagh
OCPB Reviewer
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)