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Dear group,
Assume a situation where a Bioanalytical method validation was
completed either on HPLC or LC-MS/MS.
During actual sample analysis some subject samples showed a
interfering peaks at the retention time of analyte.
1. In such cases can we change the flow rate in order to avoid the
interference ?
In another situation, detector response was changed while doing the
actual sample analysis.
2. In such case can we change Injection volume of the validated
method for the analysis
I request expert comments on this
Thank you
Regards
Rajareddy
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The following message was posted to: PharmPK
1) Changing the flow rate will change the method
2) Changing the detector response will change the method
3) Changing the injection volume will change the method
Each change means that you were no longer using the validated method and
would require revalidation, though possbily not as extensive as the
initial validation.
--
Ed O'Connor, Ph.D.
Laboratory Director
Matrix BioAnalytical Laboratories
25 Science Park at Yale
New Haven, CT 06511
Web: www.matrixbioanalytical.com
Email: eoconnor.at.matrixbioanalytical.com
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Dear Rajareddy,
1. What is required if you change the flow rate to separate newly
observed interferences from analyte (or internal standard)? Ideally
you would have shown in Method Validation that precision and accuracy
are not affected by such changes. However in the real world where
this didn't happen, you very minimally would need to run QCs at the
new condition and show that they perform as expected. Better than
just 2 at each concentration would be n greater or equal to 5 and
generate more robust supportive statistics, at least within a run.
It would also be good to analyze a few real samples that don't have
the interferent by the original method to confirm that they are still
analyzed correctly. Document the results so they become part of the
validation submitted in any filing. This has worked for my group in
the past. If the interferences become very frequent, you might
change the method (validate it as a different method), rather than
having to shift between two conditions and explain each time.
2. Again, changes in injection volume would be best to validate
during Method Validation, especially since the injection volume can
directly affect the limits of quantification. Otherwise I would
follow the path described above. You would also need to decide how
to relate the results to the calibration standard curve, if the
volume was different for the sample and calibration standards. I see
less value in injection volume changes than flow rate changes in
separating interferences.
Tom
Thomas L. Tarnowski, Ph.D.
Bioanalytical Development
Elan Pharmaceuticals, Inc.
800 Gateway Boulevard
South San Francisco, CA 94080
thomas.tarnowski.aaa.elan.com
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The following message was posted to: PharmPK
In both cases if you don't do a partial revalidation you will not have
run your samples with a validated method.
I would suggest the following:
1. Prior to rerunning the patient samples change your method to separate
the interfering peak from the peak of interest, e.g. change the flow
rate.
2. Do a partial validation, i.e. you don't have to redo stability etc..
Just determine accuracy and precision.
3. Now you have a new method and can run the patient samples if you have
any sample remaining.
Ron Kavanagh
The opinions are my own and do not reflect the opinions of the FDA.
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