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Re: [NMusers] BLQ Data

From: Li Li <>
Date: Fri, 2 Oct 2015 12:21:50 -0400

Hi Brady,

There are many papers discussing methods of handling BQL data. Below are
some examples:

[1] Ways to fit a PK model with some data below the quantification limit.
Beal SL. Journal of Pharmacokinetics and Pharmacodynamics 2001; 28:481-504

[3] Analysis of toxicokinetic data using NONMEM: Impact of quantification
limit and replacement strategies for censored data. Hing JP. et al. Journal
of Pharmacokinetics and Pharmacodynamics 2001; 28:465-479

[4] Impact of censoring data below an arbitrary quantification limit on
structural model misspecification. Byon W. et al. Journal of
Pharmacokinetics and Pharmacodynamics 2008; 35:101-116

[5] Likelihood based approaches to handling data below the quantification
limit using NONMEM VI. Ahn JE. et al. Journal of Pharmacokinetics and
Pharmacodynamics 2008; 35:401-424

[6] Impact of low percentage of data below the quantification limit on
parameter estimates of pharmacokinetic models. Xu XS. et al. Journal of
Pharmacokinetics and Pharmacodynamics 2011; 38:423-432

Also, I have conducted some analysis using real clinical PK models and will
present a poster in ACoP next Monday with a recommendation of decision tree
on handling BQL. My experience is that it really depends. If you have a
simple model with low BQL% (<10%), I think excluding BQL is fine. But if
you have a complex model with large BQL, M3 method should be considered.


Li Li

Research Scientist, Global PK/PD and Pharmacometrics

Eli Lilly and Company

On Fri, Oct 2, 2015 at 10:22 AM, Moffett, Brady S. <>

> I am working with TDM data and am wondering when to use the M3 method for
> dealing with BLQ data, or, when to just exclude data?
> For instance: If I have <1% BLQ data in a large dataset (~1000 patients)=
> should I just exclude those patients/values? If I just have one patient
> with one value BLQ, is it worth using the M3 method for that one patient?
> Is there a breakpoint for which using these methods does/does not make a
> difference?
> Thanks in advanceā€¦
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Received on Fri Oct 02 2015 - 12:21:50 EDT

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