Nanda,
My first question would be, are these cut points so high because the average sample is high, or because the variability (SD) is high?
Given the information you provided, I suspect one of two things - either you have a lot of true positives among your cut-point samples, or there is something causing a background of non-specific binding in your assay that can be competed by excess drug. In the past, I have taken an approach of eliminating any sample with inhibition >50% as being assumed true positive. Granted, 50% is a bit arbitrary, but this was for a population that was expected to have many positives.
If the problem is non-specific binding, you could try adding an irrelevant antibody, or a heterophilic blocking reagent, to your assay buffer.
John Kamerud
JKBioanalytical Consulting LLC
Original Message:
Sent: 5/27/2025 10:05:00 AM
From: Nanda Balasubramanian
Subject: Biological Outliers in ADA assay
How do you go about identifying biological outliers for an ADA assay, especially for the confirmatory tier? We have a situation where there is a screening cut point of 1.9 and a high correlation between S/N and % inhibition with a confirmatory cut point of 79%. We did apply the conventional statistical outlier removal approaches but will appreciate any insight on approaches for removing biological outliers.
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Nanda Balasubramanian
Senior Principal Scientist
Bristol Myers Squibb
Cambridge MA
[email protected]
Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
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