I'm not sure of the mechanism but Pottasium that has leached from the
red cells is forced through the gel giving falsely elevated serum
levels

This is news to me, we routinely respin SST vacutainers from our office
clients. Does it say why you should not respin them?

Gary

If I remember correctly, the aged serum below the gel layer contains a very
high potassium concentration due to its contact with the red cells.
Respinning the tube -- especially if spun initially in an angled head
centrifuge and respun in a floating head centrifuge -- forces some of the
serum in the lower level into the top layer, falsely elevating the potassium
value and the value any other analyte that would increase if left in contact
with the cells. The same criteria should hold true for any separator tube,
whether serum or plasma.

Since it takes a while for the potassium in the lower layer to leach out of
the cells, respinning a gel tube within an hour or two of the initial
spinning for the purpose of removing fibrin should be acceptable and give
you a valid potassium value. If the problem recurs frequently, either wait
longer to spin the tube (inserts usually suggest 20-30 mins, or 60 mins if
the patient is on heparin) or switch to heparin tubes so the problem is
moot.

If the tube was spun off-site and contains particulate matter or fibrin, we
routinely remove what we can of the serum layer and respin it in a separate
tube to clarify it before testing.  We do not respun old separator tubes.

Larry Smrz, MT(ASCP)SBB
Indianapolis, IN

We receive specimens that are collected at 2 offsite clinics.  They
typically bring in the specimens in the evening.  We usually respin the
SST's and have not had problems with the results.  However, if, by chance
the tubes are kept at the clinic overnight and we then respin them, we do
have problems with elevated potassium.  That has been our experience.