Compliance
★    

India,
2015-03-23 08:39
(3294 d 07:18 ago)

Posting: # 14588
Views: 11,807
 

 Change in curve changed the ratio of Cmax [Bioanalytics]

Dear All,

I request to share your comment on below issue:

We had run one 4 Way crossover study with 1-800 ng/ml and we get the ratio of Cmax 102%. We have revised the range 0.250- 250 ng/ml. we repeated the same samples which are initially run with 1-800 ng/ml.

After completion of repeat study we got ratio of Cmax 87%.

Now my question is does it impacted due to change in method (i.e. linearity) & processing volume? does the observed change in Cmax ratio is logical and acceptable or any doubt on the method can be raised?

Please note that the difference between the concentration obtain during initial analysis and repeat analysis is around 10-12%.

Please advice and share your thought on this matter.

Regards,

Compliance
Dr_Dan
★★  

Germany,
2015-03-23 09:59
(3294 d 05:58 ago)

@ Compliance
Posting: # 14589
Views: 10,706
 

 Change in curve changed the ratio of Cmax

Dear Compliance
You analysed the same samples with two different (fully validated?) methods and got two different results.

❝ Now my question is does it impacted due to change in method (i.e. linearity) & processing volume? does the observed change in Cmax ratio is logical and acceptable or any doubt on the method can be raised?


The observed change in Cmax ratio is not logical and acceptable and doubts on the method(s) can be raised.

❝ Please note that the difference between the concentration obtain during initial analysis and repeat analysis is around 10-12%.


This is not correct. If the change affected all samples you would have no difference in study results. In fact it seems that only the samples for the test formulation show differences between the concentration obtain during initial analysis and repeat Analysis. This is not logical.
I guess you have a severe Problem.
Kind regards
Dr_Dan

Kind regards and have a nice day
Dr_Dan
Compliance
★    

India,
2015-03-23 10:27
(3294 d 05:30 ago)

@ Dr_Dan
Posting: # 14593
Views: 10,705
 

 Change in curve changed the ratio of Cmax

❝ You analysed the same samples with two different (fully validated?) methods and got two different results.


Yes we have full validated method.

❝ This is not correct. If the change affected all samples you would have no difference in study results.


please note the difference is throughout the study irrespective of test and reference.
In this case i give you one example during initial study analysis one of the subject has only three period quantify and rest of the period has zero or BL Q concentration. After repeat study with the lower LLOQ, the obtain concentration is around 0.23 ng in one period and 23 ng/ml in other period of test.

Now during point estimation such difference will impact the result and there are few such kind of subjects which are gets qualify after having analysis under lower curve.

Please consider above situation.

Regards,

Compliance
nobody
nothing

2015-03-23 10:19
(3294 d 05:38 ago)

@ Compliance
Posting: # 14592
Views: 10,645
 

 Change in curve changed the ratio of Cmax

Hi Compli!

Without a thorough look on method validation reports and the slopes/intercepts as well as QC results of both analytical methods I would say nothing ;-)

But Dr. Dan is right: This sounds quite strange from the few data provided so far...

Kindest regards, nobody
Compliance
★    

India,
2015-03-23 11:09
(3294 d 04:48 ago)

@ nobody
Posting: # 14596
Views: 10,698
 

 Change in curve changed the ratio of Cmax

Dear nobody,

To the answer your question:

Please note that i have taken CV of slope and intercept and it is within the 15%. However in entire method validation, only few of the QC's are getting fail to meet the acceptance which are also marginal.

Hence i could not doubt on the method. if there is any other point which i have to take care while qualifying method, then please share with me.

Regards,

Compliance
nobody
nothing

2015-03-23 11:34
(3294 d 04:23 ago)

@ Compliance
Posting: # 14597
Views: 10,665
 

 Change in curve changed the ratio of Cmax

Hi Compliance!

Do I get this right: You basically suggest that the improved LLOQ increased the number of samples >LLOQ and thereby Cmax statistics changed dramatically?

But AUC was largely unaffected?

Was the absolute slop unaffected by changing the calibration range? Did you change weighting factors for lin. regression?

Hmm... really hard to say "no problem" based on spares data! ;-)

Kindest regards, nobody
Compliance
★    

India,
2015-03-23 11:53
(3294 d 04:04 ago)

@ nobody
Posting: # 14598
Views: 10,678
 

 Change in curve changed the ratio of Cmax

❝ Do I get this right: You basically suggest that the improved LLOQ increased the number of samples >LLOQ and thereby Cmax statistics changed dramatically?


Yes. we assume that we will get full characterization and it happen.

❝ But AUC was largely unaffected?


AUC is also get affected as the data set pool increases due to less LLOQ with respect to previous one.

❝ Was the absolute slop unaffected by changing the calibration range? Did you change weighting factors for lin. regression?


Weighting factor for liner regression is same as previous i.e. 1/x2

❝ Hmm... really hard to say "no problem" based on spares data! ;-)


this is Meselamine and giving very hard time to me. :confused:

regards,

Compliance
Ohlbe
★★★

France,
2015-03-23 15:13
(3294 d 00:44 ago)

@ Compliance
Posting: # 14599
Views: 10,667
 

 Change in curve changed the ratio of Cmax

Dear Compliance,

❝ We had run one 4 Way crossover study with 1-800 ng/ml and we get the ratio of Cmax 102%. We have revised the range 0.250- 250 ng/ml. we repeated the same samples which are initially run with 1-800 ng/ml.


Was there any change in the method apart from the LLOQ ?

Did you run ISR with both methods ? What was the outcome ?

Regards
Ohlbe
Compliance
★    

India,
2015-03-23 16:29
(3293 d 23:28 ago)

@ Ohlbe
Posting: # 14600
Views: 10,587
 

 Change in curve changed the ratio of Cmax

Dear Ohlbe,

❝ Was there any change in the method apart from the LLOQ ?


Yes. we also change the processing volume from 0.5 ml to 0.150 ml.

❝ Did you run ISR with both methods ? What was the outcome ?


yes, first set of ISR is run and found satisfactory. second set is about to run of repeat study. However ISR of initial analysis is pass comfortably with around 90% acceptance.

I would like to add one thing that, i had done comparison of Cmax data between originally run assay and repeat study and found there is a difference of around 8-10% (negative side) and the same is getting reflected in the Cmax ratio.

some of the subject which are not getting qualify with initial range i.e. 1-800 ng/ml is getting qualify with the revised range 0.250 -250 and in that one of the period of test is showing very less concentration and this is affecting the ratio.

Please note this is 4 way crossover study.

Regards,

Compliance
nobody
nothing

2015-03-23 17:11
(3293 d 22:45 ago)

@ Compliance
Posting: # 14601
Views: 10,701
 

 Change in curve changed the ratio of Cmax

❝ ...

❝ I would like to add one thing that, i had done comparison of Cmax data between originally run assay and repeat study and found there is a difference of around 8-10% (negative side) and the same is getting reflected in the Cmax ratio.



...again: did the slope differ between method 1 and 2?

And again: Nobody (not eve the real one ;-) ) can decide the results are valid without having a deep look into your lab notebooks and reports ;-)

Kindest regards, nobody
Dr_Dan
★★  

Germany,
2015-03-24 09:15
(3293 d 06:42 ago)

@ Compliance
Posting: # 14604
Views: 10,547
 

 Change in curve changed the ratio of Cmax

Dear Compliance

❝ Please note that the difference between the concentration obtain during initial analysis and repeat analysis is around 10-12%.


Again: If you use a different method the absolute concentratiosn measured in the samples can be different from method to method since bioanalytical methods are "semi-quantitative". However, if both methods are accurate and precise the slope of the curve should not be different i.e. the ratio of Cmax should be the same. When applying another method all samples are affected in the same way, there can not be a difference between test and reference samples. It is therefore absolute unlogical to have a shift in Cmax from 102% to 87% without having differences in method performance.
Kind regards
Dr_Dan

Kind regards and have a nice day
Dr_Dan
Compliance
★    

India,
2015-03-24 10:39
(3293 d 05:18 ago)

@ Dr_Dan
Posting: # 14605
Views: 10,505
 

 Change in curve changed the ratio of Cmax

Dear Dr_Dan,

Agree with your point but please consider one thing that the subject which are not getting qualify during initial analysis are getting qualify with the revised range.

In this case, the concentration obtain during repeat analysis of period which was showing zero or BLQ during initial study analysis having very less concentration. For example see below:

subject no. 13 during initial analysis showing only one period gets quantify concentration and the Cmax is around 23 ng/ml. second period of test has shown zero or BLQ. Now with the revised range both test period gets qualify and the Cmax is around 22 ng/ml (which was previously 23 ng/ml) and second period of test got Cmax 0.75 ng/ml.

Now in the point estimation of 4WC this mean of the test will affect the data.

there is some other subject also who has shown same kind of data or some deviation around 10-12% during repeat study analysis.

Now please let me know under such situation affect at the Cmax ratio is logical or not?

Regards,

Compliance
Dr_Dan
★★  

Germany,
2015-03-24 12:05
(3293 d 03:51 ago)

@ Compliance
Posting: # 14609
Views: 10,626
 

 Change in curve changed the ratio of Cmax

Dear Compliance
So the difference in Cmax ratio is due to the different number of test/reference comparisons since you now have additional profiles which were not available before due to the poor sensitivity of the first method, right?
In this case the first method is not appropriate to evaluate the study. According to the European BE guidelines the lower limit of quantitation should be 1/20 of Cmax or lower, as pre-dose concentrations should be detectable at 5% of Cmax or lower. I do not know if EMA considers the mean Cmax or the individual profiles. How many subjects/periods do you have with a Cmax between 0.25 ng/ml and 1.0 ng/ml?
However, to answer nobody´s question: The slopes of the individual profiles do not differ, right?
Kind regards
Dr_Dan

Kind regards and have a nice day
Dr_Dan
Compliance
★    

India,
2015-03-25 13:13
(3292 d 02:44 ago)

@ Dr_Dan
Posting: # 14616
Views: 10,349
 

 Change in curve changed the ratio of Cmax

Dear Dr_Dan,

❝ So the difference in Cmax ratio is due to the different number of test/reference comparisons since you now have additional profiles which were not available before due to the poor sensitivity of the first method, right?


Yes.

❝ In this case the first method is not appropriate to evaluate the study.


A product in which we are working having issue with itself. actually it is not possible to get the consistent performance in healthy subject. it is locally acting and if we need to get success then the patient is the only option. Actual suggested LLOQ in SBOA is 5 ng/ml which was used at the initiation of the study and based on the experience of each repeated study we have revised the LLOQ.

According to the European BE guidelines the lower limit of quantitation should be 1/20 of Cmax or lower, as pre-dose concentrations should be detectable at 5% of Cmax or lower.

we are working on Meselamine and conventional approach could not work.

Regards,

Compliance
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