Re: Insulin Testing - Important Update
Eleanor Kellon, VMD
I asked Dr. Barbara Schanbacher from Cornell about sample type interference in assays and her reply is below:
"The assay used for this paper was the Immulite 1000 chemiluminescent insulin assay. This assay states it does not work on EDTA samples in the package insert. We do not use it because the assay curve has very poor sensitivity and about 15% of equine samples tested have wildly discordant results compared to the RIA we use. They are unfortunately stuck with this assay over in Australia and New Zealand as one of the better options because they can't get many of the assays available in the US.
Insulin is stable in serum and EDTA and heparin plasma in the RIA we use for 1 week on cells, 2 weeks in the fridge and > 5 years in the freezer and the results are comparable for all 3 sample types. "
So, unless the lab is using a CIA assay (Immulite most often mentioned in equine papers), there shouldn't be a problem at least with the Millipore brand assays used by Cornell, Guelph, Michigan State, BET Labs. For other labs you will need to find out the type of assay being used.
Eleanor in PA