Hi Jannalee,

In tests where it is appropriate to freeze the sample, the results are reliable from a frozen sample as long as it was separated and frozen properly initially and remained so until it is processed by the lab. Not all samples are suitable for freezing.

The Insulin/ glucose/ leptin sample should not be frozen so it cannot be stored appropriately for long periods of time. Glucose is esp vulnerable to degradation when not spun and separated promptly.

I believe that is what the lab person was referring to when s/he spoke to your vet. It seems as if the conversation may have been a bit vague in the details. Here are the instructions for sending the samples correctly directly from Cornell's website:

https://ahdc.vet.cornell.edu/docs/Test_and_Fee_List_Equine_only.

If I'm wrong, I'm sure one of the specialists here will correct me.


Lavinia, Dante, George Too and Peanut
Jan 05, RI
EC Support Team

Thanks, Dr. Kellon and Lavinia,

I think the vet knew/knows that the insulin/glucose/leptin don't need to be frozen; she is looking for a way to make her day easier, in general, and to be able to schedule blood draws any day of the week, rather than the Mon/Tues that I always suggest.

It sounds as if we just freeze it once, i.e., after spinning/separating per Cornell's instructions, and send it via FedEx the same day, it will be fine.

Clearly, that's not what Cornell recommends, but if this is the only way to get it done (most of our vets are still recommending fasting blood draws and use IDEX labs), and the results won't be affected by a one-time freeze, then that's what we'll do.

Thanks again for your prompt replies.

Jannalee
Talent, OR
2008

Ideally the serum tube is kept chilled on ice packs in an insulated shipping box en route to Cornell. Having talked to the lab myself, it wont hurt the serum to be frozen--its getting too hot that is the real problem

The abnormally low glucose results are caused by the length of time the reb blood cells remain in contain with the serum component of the blood (the fluid part that the RBCs are suspended in). The RBCs literally digest the glucose for energy so therefore making your sample horse's glucose result lower than what it truly is. Thats why its imperative to centrifuge the tube asap. However, the RBCs have to form a clot before they can be spun down, and that can take anyway from 1min to sometimes 30 mins. IMO the only glucose that is accurate is one done by veterinary glucometer at time of draw. I no longer rely on glucose results from the tubes sent out to labs for G:I ratios, etc. The disparity in results is unequivocal in the experiments ive done so far (checking glucometer results vs lab results on same blood sample). Please note thats my personally experience only, and not necessarily the group's opinion. The reason Ive been experimenting w glucometer results is my PPID mare is routinely hyperglycemic on glucometer but often "normoglycemic" on same sample commercial lab results, and with her initial borderline ACTH result the hyperglycemia was what finally got my local vet on board w the PPID diagnosis. Personally im concerned we--as veterinary professionals--are not catching hyperglycemia bc of the limitations of our current field glucose testing and therefore the primary vets may be less likely to consider early PPUD without the hyperglycemia as a nod toward PPID. FWIW, the theory saved my mare's life and thats why im pursuing it

Kerry in NY
Lic Vet Tech
Sept 14