working with is trying to get us to send them serum instead of plasma, but it is easier for us to use plasma. Do you have an opinion on which is better?
JEFFREY ROSSIO: We have done a lot of measurements both ways. Plasma is usually easier to get and more available. We haven't had a lot of trouble in measuring cytokines in plasma. So, probably you have to talk to the laboratory and see if they have a problem with standardizing their assays one way, and they don't want to go to the trouble of standardizing them again or not. We haven't found interfering substances.
Now, in some of our studies in cancer patients, we have gone to the extent of doing a double molecular filtration to remove everything with a molecular weight of over 50,000 and everything under a molecular weight of 15,000 or 10,000 with centrifugal filters to see if there were inhibitors around that were affecting our results. The conclusion of that study was that it was not worthwhile to go to the trouble of performing a double molecular filtration.
DAVID NIEMAN: One follow-up question. Immediately after heavy exertion when we take a sample and separate the plasma and try to freeze it within 30 minutes, on doing that we find that IL-6 goes up about sixfold. Is there anything you can recommend like deliverance timing for freezing, or is 30 minutes okay?
JEFFREY ROSSIO: I don't know. We usually just recommend as fast as possible. I think 30 minutes is probably okay. When cytokines are present in low concentrations, like any protein in low concentration, they have a tendency to adhere to glass, to adhere to polystyrene. So, we are usually trying to do it as quickly as possible and get it frozen as quickly as possible.