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Dear Group,
Are there any guidelines/conventions in terms of minimum sample size
that can be accepted by bioanalytical laboratories? My contention is,
there should always be a reserve sample available for repeating
analysis, in case of instrumental failures, unexpected results etc.
This issue is critical when limited sample availability is there like
discovery mouse PK studies. Let me know the group's experience.
Regards,
Vinayak
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Vinayak, ideally that is how things should work, but sometimes it just
isn't
possible. Sometimes larger sample sizes are required to achieve desired
levels of detection, and especially with mouse plasma samples, it is
easy to
utilize a good deal of sample and not have enough for repeat analyses.
I am
not aware of any guidelines that specify that enough sample should be
retained for repeat analysis, except for the recent incurred sample
reanalysis (ISR) guidelines, and they are not applicable in discovery
PK.
Mickey
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Several considerations
1) Assay minimum sample volume requirement
2) Maximum blood draw permitted for 24 hour period
3) Number of timepoints
4) Number of sample splits/timepoint
5) Volume needed to assess clinical biomarkers
Number 2 is the limitation but all points need to be addressed so as
not to exceed 2
Usually during development you determine the volume for #1 while #5 is
set. From #1 you can determine the number of samplings (3 to 5
replicates from that tube and use this to set your requirement for the
split volume. Cannot exceed #2.
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Dear Vinayak
Sample size of the important parameter in method validation. it
depends on the
1. nature of drug (response to the detector)
2. Bioavailablty factor of drug
3. Dose
4 extraction procedure (recovery)
4. method of analysis (HPLC, LC-MS etc)
Then it ispossible to define the sample size and ideally it must be at
least close to or above LOQ value
Dr Zafar
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