‘Embedded’ BQLs [Bioanalytics]

posted by Helmut Homepage – Vienna, Austria, 2022-03-28 14:32 (183 d 08:58 ago) – Posting: # 22880
Views: 649

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)?

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.

Dif-tor heh smusma 🖖 Довге життя Україна! [image]
Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes

Complete thread:

UA Flag
 Admin contact
22,391 posts in 4,685 threads, 1,595 registered users;
online 4 (0 registered, 4 guests [including 4 identified bots]).
Forum time: Tuesday 23:31 CEST (Europe/Vienna)

Statistics. A sort of elementary form of mathematics which consists of
adding things together and occasionally squaring them.    Stephen Senn

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz