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Extract from Regulatory and Safety Evaluation Specialty Section
RSESS) Newsletter Winter 2007.
"Unexpected Controversy on Best Practices for Bioanalytical Method
Validation and Implementation"
Recently, an AAPS workshop was held to review and consider updates to
the guidance for bioanalytical method validation and implementation
(Crystal City III meeting, May, 2006; http://
www.aapspharmaceutica.com/meetings/pastmeetings). The meeting
focused on "best practices" for both chromatographic and ligand
binding bioanalytical methods.
Some of the topics discussed at the included:
Standards and quality control (QC) criteria
Best practices and acceptance criteria for method validation
Acceptance criteria for analysis of study samples
Similar topics were also discussed for chromatographic assays except
the focus was somewhat different, for example:
Spacing of QC standards for analysis of study samples
Concerns for the accuracy and reproducibility of bioanalytical results
Automated and manual chromatographic peak integration methodology
However, the topic that generated the most controversy was a proposal
for the "reanalysis of incurred samples". This proposal was presented
in the context of a discussion of sample assay
reproducibility and "what needs work"?. Reanalysis of incurred
samples refers to the reanalysis of a randomly selected portion of
the study samples to determine whether the original analytical
results are reproducible.
The amount of the original analyses to be reanalyzed was not
determined. Ideally, the validation of the bioanalytical method would
have established reproducibility of the analytical results prior to
the sample analysis. This additional effort would be unnecessary,
but the "reanalysis of incurred samples" implies additional test of
reproducibility for each set of unknown study samples that are analyzed.
Although the technical bases for a lack of assay reproducibility were
not clearly expressed, possibilities might include:
(1)the presence of an unstable metabolite(s) in the study samples
that could decompose and release the analyte(s)
(2)variability in the sample preparation procedures.
Ideally, both of these potential issues would be addressed during the
validation of the bioanalytical method and by adherence to good
laboratory management practices.
However, comments by regulatory agency meeting participants suggested
that lack of sample assay reproducibility had been observed randomly,
and that additional assurances of study data
integrity using incurred sample reanalysis are needed.
In summary, this technical discussion of best practices for
bioanalytical method validation and sample analysis produced an
unexpectedly spirited discussion of the most appropriate way to
demonstrate the reproducibility of bioanalytical results. A
scientific and regulatory consensus on this issue has yet to be
defined, but in the interim, it appears that sponsors are expected to
initiate a practice of routinely reanalyzing a subset of incurred
I would like to know what are the members experience with the above
and/or comments on reanalysis of incurred samples.
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The following message was posted to: PharmPK
Thanks for bringing to my attention that the FDA guidance on
bioanalytical method validation and implementation is under review.
I have no opinion about 'incurred samples' - an expression which has
no easily understandable meaning for me in the English language.
But I do feel strongly that the FDA guidance should make it clear
that the common practice of not reporting measurements less than the
lower limit of quantification is seriously bad science because of the
inevitable bias it introduces.
By all means chemical analysts may estimate a LLOQ value for quality
control purposes but please don't throw away valuable information
(i.e. BLQ measurements) for those of us who do pharmacokinetic
analysis and are capable of interpreting values less than a limit
recommended by regulatory guidance for a quite different purpose.
(see http://www.boomer.org/pkin/PK05/PK2005184.html for a discussion
on PharmPK of the issues as seen by pharmacokinetic analysts)
Nick Holford, Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New
email:n.holford.-at-.auckland.ac.nz tel:+64(9)373-7599x86730 fax:373-7556
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In my personal and honest opinion the controversy regarding the
incurred samples as QCs is rightfully justified. as the 2000
Bionalaytical guidance is working fully well like a well oiled
machine. Introducing this incurred samples analysis as a requirements
throws monkey wrench on the usual way of sample analysis.
The merits of introducing incurred samples as additional QC measure
for establishing the robustness of the method is that The QC are
usually prepared from health subjects but not from the sample
population as that of study subjects. Fine... we do method
specificity and sensitivity for this same reason, rule out the
interferences from OTC products and metabolites of the drug under
investigation and metabolites of any other co administered drugs.
Having said this, School of thought proposing this incurred samples
analysis should be aware of sampling limitations those it mean
additional pre-dose blood collection, can we do incurred samples from
cancer subjects???, even on theoretical basis there seems to have
some merit of doing incurred sample analysis as part of the routine
sample analysis, in my honest opinion it is nothing but an academic
mulch, with remote and doubtful advantage in the NDA work of New
Medical Entities and lignad binding assays for Biotech products. But
what is the rationale of introducing incurred sample analysis for
It is not an unexpected controversy but it is a controversy generated
out of its own roots. I wish someone will take up the issue with the
concerned folks to the FDA and other global regulatory agencies to
gain exemption from this controversial incurred samples if not in
entirety at least for generic products.
Hope this explanation helps.
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