Drug concentration <LLQ [Bioanalytics]

posted by Ohlbe – France, 2018-06-29 14:00 (2155 d 17:16 ago) – Posting: # 18995
Views: 2,871

(edited by Ohlbe on 2018-06-29 17:11)

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]


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