# BLQ rule

**URL:** <https://forum.certara.com/t/blq-rule/3421>\
**Category:** Phoenix WNL basics\
**Created:** [June 19, 2019, 9:34am UTC](https://forum.certara.com/t/blq-rule/3421 "2019-06-19T09:34:31Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mvanzutphen](https://avatars.discourse-cdn.com/v4/letter/m/22d042/32.png) [@mvanzutphen](https://forum.certara.com/u/mvanzutphen)\
**Post date:** [June 19, 2019, 9:34am UTC](https://forum.certara.com/t/blq-rule/3421/1 "2019-06-19T09:34:31Z")

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Hi,

I’m working on an NCA and the client asks to implement some LLOQ rules, I would like to add PK concentration column with the substituted values in my dataset.

1.LLOQ before Tmax = LLOQ/2

1. first LLOQ after Tmax = LLOQ/2

2. all subsequent LLOQ values should be missing

LLOQ = 45

I’m using PHX 8.1 and struggling with the BQL Rules option (never had to use it before).

Attached is a subset of the data.

Could you please advize on how to fill in the BQL rules?

p.s. the client data shows LLOQ/2 for CONCN when CONCT(text) \<LLOQ, but now they want to implement the new rule but not update their dataset.

Thanks very much in advance

[sel variables, properties.xls](https://forum.certara.com/uploads/short-url/gsD6inf2Op4v6DPXYPcdU2b8Cxl.xls) (195 KB)

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**Author:** ![SimonDavis](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@SimonDavis](https://forum.certara.com/u/SimonDavis)\
**Post date:** [June 19, 2019, 1:01pm UTC](https://forum.certara.com/t/blq-rule/3421/2 "2019-06-19T13:01:32Z")

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Mariëlle, I wasn’t sure but I think this will get you what you /your clinet wants. the sample data set has some interesting things. e.g.

1. do you really want to assign a numeric value to time zero e.g predose?

2. assigining numeric conc values pre Tmax means you won’t have an estimate for tlag.

3. I see the data has a late Tmax, but not very much data to really test if I am setting up the rules correctly for later samples.

Simon

PS next time posting an actual project would be easier.

PPS this is a v81 project but rule is also shown in this screenshot

[Marielle\_BQL.phxproj](https://forum.certara.com/uploads/short-url/oaf4d1aeADgSbKfXfqDGXDmMJpQ.phxproj) (511 KB)

 ![Marielle_BQLrule.jpg](https://us1.discourse-cdn.com/certara/original/2X/8/83e30861598de3515293e97082291b926f208ea1.jpeg)