Loky do
★    

Egypt,
2022-03-28 14:16
(845 d 00:45 ago)

Posting: # 22873
Views: 2,395
 

 BLQ considerations [Bioanalytics]

Dears

Regarding BLQ samples in the middle of plasma concentration curves, which remain BLQ after reanalysis, what is the best practice for those samples in calculations? To be considered as (missed or Non-reported samples or blank)? Or to keep it as it is <LLOQ?

Thanks in advance


Edit: Merged with a later (now deleted) post. You can edit your posts for 24 hours. [Helmut]
dshah
★★  

India/United Kingdom,
2022-03-28 16:14
(844 d 22:47 ago)

@ Loky do
Posting: # 22877
Views: 2,024
 

 BLQ considerations

Hi Loky do!
It is best to consider as per the SOP procedure of CRO.
IMHO, it can be considered as non-reportable samples.
Regards,
Divyen Shah
Helmut
★★★
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Vienna, Austria,
2022-03-28 16:32
(844 d 22:29 ago)

@ Loky do
Posting: # 22880
Views: 2,047
 

 ‘Embedded’ BQLs

Hi Loky do,

❝ Regarding BLQ samples in the middle of plasma concentration curves, which remain BLQ after reanalysis, what is the best practice for those samples in calculations?


My personal points of view…

❝ To be considered as (missed or Non-reported samples …


Why? You measured them (confirmed even in a second analysis).

❝ … or blank)?


:confused:
Do you mean setting them to zero? If yes, that would not make sense.
BTW, replacing BQLs by LLOQ/2 does not make sense either.1

❝ Or to keep it as it is <LLOQ?


Any nonnumeric code would be fine.2 However, I recommend to give them with the more common code ‘BQL’ and use the linear-up / logarithmic-down trapezoidal rule. If you use the linear trapezoidal rule, the AUC will be positively biased (i.e., the value ignored and a trapezoid calculated connecting the time point before and after with a straight line). See this article (esp. the example about missing values).

Of note, the lin-up/log-down trapezoidal is recommended in the trainings for Phoenix/WinNonlin (Certara) and PKanalix (LIXOFT). It is the default in the [image]-packages bear, PKNCA, and ncappc.


  1. I use it only for plots since I always give the geometric mean.
  2. If you want to make assessors, inspectors, and consultants happy: Use more informative codes in the bioanalytical report, e.g.,
    • ‘BQL’ for values which where <LLOQ,
    • ‘NR’ for not reportable ones (say, problems in sample processing or chromatography),
    • ‘missing’ for no sample (vial broken, etc.).
    All nonnumeric codes are ignored in software. However, data pretreatment is a must. A common procedure is to set all nonnumerics before tmax to zero and keep the code for later time points.

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