Detection and quantitation limits for assay method

[35manikanta]

hello veryone!

can anyone please suggest me .....when any health authority asks to submit data of LOD and LOQ for an assay method....?

[Consumer Products Guy]

In my opinion, LOD and LOQ are "interesting" parts of cGMP method validation, because there apparently are not a pass/fail criteria. But it helps show that you've done decent investigation into your test methodology.

For example, if your working range is very close to your LOQ, likely not as good as if your working range is 100 times or 1000 times your LOQ.

[35manikanta]

Thank you for your reply

........and my doubt is according to ICH Q2- its not necessary to provide such data for an assay method and my working concentration is far above the two levels and and in my opinion this is a baseless question from HA.

[Don_Hilton]

It is not unreasonable for a regulatory body to ask for LOD and LOQ. I have seen results reported below LOQ - and perhaps from noise (mark that asdisregard for LOD)... This was not in a regulated laboratory, by the way.

[tjb]

hello veryone!

can anyone please suggest me .....when any health authority asks to submit data of LOD and LOQ for an assay method....?

If by assay method you mean stability indicating assay (deg) method? For these methods there is a requirement to establish the ~0.02% (LOD) and ~0.05% (LOQ) nominal levels,assessing reproducibility or signal to noise and linearity down to the LOQ level.

If you had a content only method (assay only or dissolution), then you would not need this, your linearity range (50 - 150% nominal) would cover the intended purpose of the method.

If however your method combines assay and degs, then yes it would be a regulatory requirement.

[35manikanta]

Thank you very much

[HPLCaddict]

hello veryone!
If by assay method you mean stability indicating assay (deg) method? For these methods there is a requirement to establish the ~0.02% (LOD) and ~0.05% (LOQ) nominal levels,assessing reproducibility or signal to noise and linearity down to the LOQ level.

Erm, really? Where did you get this from? I'm not aware of authorities generally demanding these absolute values for LOD and LOQ. And I don't think it would make much sense. The necessary levels for LOD and LOQ depend on the requirements of the analysis method. If you want to quantify an impurity with a specification of NMT 1.0%, why should you be forced to use a method with an LOQ of 0.05%? On the other hand, if there's a very toxic impurity with a specification limit of just 0.05%, then a LOQ of 0.05% would be questionable.
ICH Q2 guideline just says something like "LOQ and reporting limit have to fit together", i.e. LOQ must be lower than the reporting limit.
Furthermore, if i remember correctly then according to this guideline you need for a quantitative impurity method only LOQ, LOD is optional. For a limit test, it's vice versa.