Drug concentration <LLQ [Bioanalytics]
Dear GM,
» As per the Bioanalytical guidance of FDA, all values <LLQ should be declared as zero.
»
» But my doubt is, is there any possibility to use the actual values measured for calculating key parameters?
In BE ? Not the slightest. Nada. Forget it.
» B’coz, we are not getting best fit (Rsq<0.8) when considering zero instead of actual values.
So what ? Who says it has to be < 0.8 ?
The question is rather: was your LLOQ low enough ? What you're describing sounds a bit like you're not able to follow the terminal elimination phase but are getting a mix of distribution + elimination. If you messed up, you can't make up for it by extrapolating below your LLOQ, you'll have to re-develop your method, validate, re-assay.
What is your LLOQ, and what is the Cmax range in your study ?
Edit, to make sure there is no misunderstanding: when you write
» B’coz, we are not getting best fit (Rsq<0.8) when considering zero instead of actual values.
I hope you're not using these values as 0 to calculate Kel, right ? These sampling points should just be ignored. They were to be reported as 0 in the tables of the concentration in the report, not to be used as 0 in the calculations. As pointed out by Helmut, in any case they now have to be reported as BQL. [Ohlbe]
» As per the Bioanalytical guidance of FDA, all values <LLQ should be declared as zero.
»
» But my doubt is, is there any possibility to use the actual values measured for calculating key parameters?
In BE ? Not the slightest. Nada. Forget it.
» B’coz, we are not getting best fit (Rsq<0.8) when considering zero instead of actual values.
So what ? Who says it has to be < 0.8 ?
The question is rather: was your LLOQ low enough ? What you're describing sounds a bit like you're not able to follow the terminal elimination phase but are getting a mix of distribution + elimination. If you messed up, you can't make up for it by extrapolating below your LLOQ, you'll have to re-develop your method, validate, re-assay.
What is your LLOQ, and what is the Cmax range in your study ?
Edit, to make sure there is no misunderstanding: when you write
» B’coz, we are not getting best fit (Rsq<0.8) when considering zero instead of actual values.
I hope you're not using these values as 0 to calculate Kel, right ? These sampling points should just be ignored. They were to be reported as 0 in the tables of the concentration in the report, not to be used as 0 in the calculations. As pointed out by Helmut, in any case they now have to be reported as BQL. [Ohlbe]
—
Regards
Ohlbe
Regards
Ohlbe
Complete thread:
- Drug concentration <LLQ GM 2018-06-29 05:47 [Bioanalytics]
- Drug concentration <LLQOhlbe 2018-06-29 12:00
- Report as BLQ Helmut 2018-06-29 12:15
- Report as BLQ jag009 2018-06-29 20:49
- Report as BLQ Helmut 2018-06-29 21:00
- Report as BLQ jag009 2018-06-29 20:49