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I was wondering if there were any guidelines stipulating the placement
of calibration standards during an analytical batch/run. I know that
quality controls require placement to detect assay drift, but is the
same applicable to standards?
Regards,
Jennifer Norman
Jennifer Norman
--
QA Manager
Division of Clinical Pharmacology
University of Cape Town
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It would be nice to randomize, but from a practical standpoint, the
analyst
is often hard put to get things into the plate efficiently. If you add
standards to that the mix gets a lot worse. With automation you can
theoretically sample from any well at any time-LC autosamplers. The
limitation though is carry over. This can be from a high sample
corrupting a
low standard or a high sample corrupting a low sample. With
Tecan-Multiprobe-Hamilton you can place a sample anywhere on the plate
then
develop. Carry over needs to be addressed here as well. In the end you
still
need to resolve the result with the sample and that can get dicey,
even with
automation a laboratorian is responsible for actually placing the right
sample in the right spot. Apart from that, the aaps white papers
suggest
the sequence is from low to high at the front end of a sequence,
followed by
several blanks which would show carry over. Some labs use a separate
set
of calibrators or re-inject the calibrators run initially at the front
at
the end and run either low to high again or high to low. Most ligand
based
(parallel) assays run one curve of duplicates deployed in the first
columns
or rows of a plate.
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Hi Jennifer,
Our practice is to process the standards in a seperate batch but when
we prepare the acquisition batch to be injected, we scatter the
standards amongst the unknown samples. for eg, if there are 8
standards and 40 unknown samples,
then we add a standard after every 6 unknown samples (unknown samples
also include QCs in this case).
Warm regards,
Noel
Accutest Research Laboratories,
Navi Mumbai, India.
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Dear Jennifer,
There is no clear batch organization defined in any of the validation
guidelines for CC and QC samples. But as per USFDA Guidance for
Industry on Bioanalytical Method Validation, May 2001 : "It may be
important to consider the variability of the matrix due to the
physiological nature of the sample. In the case of LC-MS-MS-based
procedures, appropriate steps should be taken to ensure the lack of
matrix effects throughout the application of the method, especially if
the nature of the matrix changes from the matrix used during method
validation."
Considering the same and inherent limit of mass spec (i.e. Drift in
response during long analytical batches), it is always better approach
to disperse the calibration samples through-out the analytical batch
(similar to QC samples).
Regards,
Kuldeep Sharma
DMPK Lab.
Jubilant Biosys Ltd.
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I and most others would have issues with the separate batch approach.
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Hi
i dont think any guideline that says the placement of calibration
standards during the analytical batch, but if anybody wants to detect
the assay drift one better way to place one calibration standards in
the last of batch, by which we can detect the drift by comparing the
area ratio of STD1-1 & STD1-2.
kanchan
veeda clinical research
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