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Dear All,
Could
I have a few queries on slopes in a bio analytical GLP, non-GLP setup as below:
1. Could any of you suggest if inter day or intra day variation in slopes acceptable?
2.If acceptable what would be the limits.
3.Can inter day variation in slopes lead to a significant deviation in PK parameters (Bio availability,t1/2 etc.) if IV and PO have been quantified with different calibration curves.
All the above are related to Mass spectrometric detector.
Thanks,
Abhijith Rao
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dear abhijith,
There is no limit for slope variation, but if you see the data for slope of a series of CC (processed iner-intra day), it will be same upto second decimal only if your method is rugged and reproducible and QC's are well with in acceptance +10%.
If your slope varies it clearly create doubt on your method. ashish saxena
INDIA
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Dear All,
Could you please emphasise more on such occurances in a discovery scenario where no method validation is involved; and we also see that PO and IV may be dosed on different days and may have to be analysed with two different curves. A difference in slopes in this process may directly influence Bioavailability numbers!
Thank you,
Abhijith Rao
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There are not requirements relating to slope specifically in GLP or non-GLP. Each of the at least six surviving curve points must return within a specified accuracy and, if replicates are used, a specified precision. The set must also include a number of QCs selected to challenge the curve and these must also return values within specifications for accuracy and precision.
If you run discovery curves without any acceptance criteria, and do anything with the data, you deserve the uncertainty!
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The following message was posted to: PharmPK
Dear Abhijith,
It's a very common problems associated with preclinical set up, where method is not validated. Now come to your queries.
1. Inter day and intra day variation is slop is acceptable or not?
Ans: It depends. You have to investigate the reasons for slope change. Whether this is due to IS variation, error in CC spiking or due to response down? For example, if it is due to IS variation or MASS response down: There will be no change in result. Your data will be acceptable. But if one person prepared CC with wrong spiking and another person processed samples correctly, then result will hampered. In short you have to first investigate for the change in slope.
2. Limit: There is no limit in any guideline, but should not deviate much in inter day run. A SOP needs to be there for CC acceptance criteria.
3. Different day variation: Already discussed above. You will be in safer side if you can run IV and PO samples under one CC. Results are acceptable if you run samples (IV and PO both) inter day with change in slopes, if you have proper justification.
If you can validate your method and prove that it will not have any impact in the results, then no body questioned you. For that, you can use different conditions (Change in buffer, MP, Processing techniques etc) to change the slope. Run the same IV and PO samples in different days. Check the results. Proved that, results are similar though there is a change in slopes.
Hope this will help.
Regards,
Sudipta Basu
Senior Research Scientist (DMPK)
Sai Advantium Pharma Ltd., Pune
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When you say "different" do you mean different curve points, or same points but different days. Do you run any sort of suitability challenge? QC and curve point acceptance?
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Dear Abhijith,
1. Variations in slopes are invitable and are acceptable
We have to ensure that variation will be minimum (depends on method ruggedness)
2. I think, Limits are not specified any where
3. May not contribute much in to the % F and T1/2. However it is prefered to run IV and PO under the same Calibration Curve.
Hope this helps you
Thanks & Regards
Raja Reddy Kallem
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A question just clicked while reading this, whether slopes of calibration curves prepared in different sources of matrix can be compared to examine the matrix effect?
Thanks and warm regards
Shital.
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Again, slopes are secondary. The CV and RE of the returned concentrations associated with the curve points in the working range and of the returned concentrations of the quality controls are what you should judge performance by.
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Shital,
I feel it is indeed a good idea. But you may have to put in more efforts when compared to preparation of QCs?
Regards,
Abhijith Rao
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The following message was posted to: PharmPK
There may be a statistical method on this issue. An F test can be used
to determine if two (or more) curves are comparable. The idea is as
follows,
1. Fit all your curves individually and obtain the residual sum of
squares (SS1).
2. Fit all your curves simultaneously with some parameter(s)
constrained (e.g. all curves share the same slope) and obtain the
residual sum of squares (SS2)
SS2 usually is larger than SS1 but with more degrees of freedom (df)
because SS2 is calculated from a fitting with less parameters.
F=SS2/SS1
This idea was originally proposed by Munson and Rodbard in 1970s. It's
worth to mention that some statisticians have doubt on this method for
non-linear regression.
Hope this helps.
Jun Shen
Senior Pharmacokineticist
Seventh Wave Laboratories
Chesterfield, MO
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