When used the immunoassay method, several metabolites are able to interfere with salivary cortisol determination especially in sample from neonates, therapy replacement, oral prednisolone use etc.
So we would like to know when its necessary to practice extraction. If possible, I would like to have a paper or personnal communication about the subject.
Best regards.
Dear Dr Alex
This sort of bacteria is not pathogenic,it is non pathogenic contaminant.It causes pseudohaemoptysis whicn is might seen in sputum pathological speciment.This red pigment ca be very useful in biological pollution tracing.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3671736/pdf/ISRN.TOXICOLOGY2012-942804.pdf
The above link is to a paper of ours where we looked at potential assay matrix issues. One of the largest concerns with steroid H's is the potential for organic contaminants to cross-react with the antibody. Inactive cortisone is probably one of the largest concerns, though it is my belief that if one could extract out cortisol and leave behind related metabolites, then you should use that method as your assay. The same goes for estrogen in my view.
We have done multiple serum cortisol ELISAs and not experienced an issue with organic contaminants. Years prior, I assisted a graduate student with a salivary cortisol assay, we did not perform solvent extraction, and those data came out fine.
I think that one of the tests you could run would be to dilute some control/ experimental/ cortisol-spiked samples across a fairly large serial spread, run them through the assay, and look for the ELISA data showing no dilution effect. It would bother me if after correcting for dilution factor the calculated values diverge by more than half of the serial dilution factor.
Dr Stephen,
Thank you very much for your answer.
We have performed a direct assay of cortisol in untreated saliva (only centrifugation was done). Spiked sampls were progressively spiked with standard but a significally deviation was shown. Theorically and measured values were signifcant different by t-test.
So i think to practise solvent extraction followed by colomn purification.
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