My Immunoassay is giving higher analyte concentrations for the same sample before plasma separation vs after plasma separation. For instance, I run my assay with whole blood, and I get a reading, then once i separate the whole blood from the plasma and just run the assay with the plasma, i get a reading that is ~20% lower. Usually this does not happen. Can anyone explain what is happening, and perhaps provide a solution? Thank you!
Do you have an alternative method to test your analyte? or better do you have a sample of known concentration? it could be that there are interference on the analysis when you run whole blood. what you could try to do is spike your analyte in the a whole blood sample and the plasma separated from the sample (while you do not know the initial concentration, you would know how much you added of the analyte) and calculate the ratio change. Also make sure that the analyte concentration is in the linear range of your assay otherwise your result will be a mess.
Something in your whole blood could be cross reacting in your immunoassay. Whatever it is, it is gotten rid of after plasma separation and the analyte reduction you see could be the loss of this non-specific signal. The only way to confirm this is to run a spiking study like Hanna Alalam suggested.
Hi Aaron Joseph Russo . Whole blood and plasma are difficult to work with since their quality deteriorates rapidly with time and storage conditions. Can you use serum? Serum is more stable and a whole lot easier to work with.
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