Odd QC values but not outliers [Bioanalytics]

posted by Thi Nguyen – Australia, 2017-09-19 15:14 (2382 d 00:33 ago) – Posting: # 17816
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Thank you so much Ohlbe for your reply!

We are trying to identify the cause of the issue and focusing on the contamination. Few tests have been done such as extracting LLOQ at the same time with ULOQ by different analysts. The result of first analyst showed perfect clean, no-contaminated, consistent LLOQs (6 replicates). The second batch from another analyst is running right now.

LLOQ and all other QCs (LQC, MQC, HQC) were prepared in bulk by spiking solutions into 10 ml plasma then aliquoted into small vials (enough for 2 replicates in assay) so LLOQ are homogenous, it shouldn't cause one very high, another from the same vial normal.

And yes, the concentrations measured match with the nominal concentration (accuracy were quite good, most of them around 100%). The abnormal only happened with LLOQ, but not with any other QCs.

No carry-over was observed at all, and the LLOQ with high values were not following any ULOQ in the run.

Agree with you that there are plenty of possible reasons and aspects to look at. That is my concern: If we can't identify any causes, what should we conclude about the method?
Could you please advise how you do in this case in your lab?

Thanks and best regards,
Thi Nguyen

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