We have recently noticed a problem with the BD SST tubes when repeating some potassium levels after they had been stored at 4 degrees C for a few days. The potassium levels were noticeably higher, and did not agree with previous stability work.
BD were contacted who implied that the potassium is only stable for 48 hours, after which it increases (so much for the inert barrier then), and that if the blood has not clotted for 30 minutes before spinning, that you can see red cells in the gel and on the upper surface of the gel.
A quick eyeball of the sample coming off the instruments showed that almost every tube had red cells within the gel, and a monolayer of red cells on the upper surface. Probably the reason for the increase in Potassium levels. However, most of the samples we looked at were from GP practices, collected by courier, so would have been sitting around for far longer than 30 minutes before being spun down.
No-one here recalls seeing this before, so I am asking if other people are seeing the same phenomena, or is this a gel batch problem which we should be taking up with BD?
I would appreciate it if people using BD SST tubes could look at a number to see if they are seeing this also.
Thanks,
Gary Mascall
Worcestershire Acute Hospitals NHS Trust.
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