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Dear All,
Can anyone provide me guideline for the quantifiation & validation of endogenous compound
where endogenous level is very high. The approah which we are following is processing
calibration standard in charcoal strip plasma & QC in authentic plasma. For quantification
6 ZS sample is processed in authentic plasma & injected its conc, is found frm the strip
curve the mean of this endogenous level is added to the QC concentration for e.g if my
LLOQ is 10pg & endo level is 50pg then for quantifiation LLOQ conc is consider as 60pg. Is
this approach is valid.
Regards,
Vishal shah
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The following message was posted to: PharmPK
Hi,
> Can anyone provide me guideline for the quantifiation& validation of endogenous compound
> where endogenous level is very high. The approah which we are following is processing
> calibration standard in charcoal strip plasma and QC in authentic plasma.
Its not clear to me why you are trying to remove the endogenous
compound. Are you trying to do a PK study of the same compound
administered exogenously? If so then it is simple to do the PK analysis
by measuring endogenous + exogenous at the same time. The PK analysis
will then estimate the endogenous baseline + time course of exogenous.
Nick
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Dear All,
Can anyone provide me guideline for the quantification and validation of
endogenous compound where endogenous level is very high. The approach
which we are following is processing calibration standard in charcoal
strip plasma & QC in authentic plasma. For quantification 6 ZS sample is
processed in authentic plasma and injected its conc, is found from the
strip curve the mean of this endogenous level is added to the QC
concentration for e.g if my LLOQ is 10pg and endo level is 50pg then for
quantification LLOQ conc is consider as 60pg. Is this approach is valid.
Regards,
Vishal shah
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Dear Vishal,
When endogenious level is 50 pg, how come LLOQ can be 10 pg?
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Dear Vishal
I think the best approach will be constructing calibration curve using
corrected area ratio vs. theoretical concentration ratio (analyte to
IS).
Area ratio of standards and quality control samples can be corrected by
subtracting mean area ratio of few ZS (zero samples) from each
calibration standard and quality control samples.
This approach will give much accurate concentration of unknown
In the approach what you have suggested utilizes apparent concentrations
in ZS, because you are back calculating the ZS samples from the CC in
which unknown amount of endogenous analyte is there.
I love to discuss if any body have other ideas too
Best regards
Rajanikanta Sahu
Research Scientist(DMPKT)
rajanikanta.s.-a-.saiadvantium.com
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Dear rajanikanta Sir,
Can you please elaborate your views about endogenous compound quantitation.
I would say our consideration, rather its an assumption, that in each
plasma aliquote we have same concentration of endogenous compound
whether it really holds the same while doing cross-validation..?
regards
Chandrashekhar
Research Associate,DMPK
Sai-Advantium Pharma Ltd.
Pune
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This is a nice approach. However, generally endogenous species exhibit
diurnal variation. In that case probably this approach may not work??
Any thoughts on this?
Cheers,
Ravi
[You can include the baseline as a sin wave function in the model during
your PK analysis if you have enough information, parameter type 20
http://www.boomer.org/manual/ch04.html#4d
- db]
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Hello Guys,
This is a good topic to discuss,
Approach 1:
Subtracting area ration of zero standard (blank spiked with IS) samples
(mean of minimum three) from the samples/calibration curve gives you
exact area/conc. of the calibrator.
Approach 2:
Treat the samples with charcoal to remove the area of endogenous
compound and then construct the calibration curve however there are some
issues with this method.
Need to take care about sample pretreatment and strategy to handle variation.
Regards,
Sudipta Basu
Principal Scientist
Sai Advantium Pharma Ltd., Pune
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If you are lucky to have a stable-labeled standard, isotope dilution
works best. If not, use standard addition approach. All other approaches
require that you make assumptions of unknown validity.
Regards,
Andrew Volosov
Shire HGT
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