Recently I sought views on this infrequent but alarming problem. Three
possibilities were advanced; our thanks to those who responded:
(a) carry-over from Hep C-antibody kits, which apparently contain gentamicin
[not likely in our case]
(b) fibrin clots from plasma or serum [see below]
(c) incorrect specimen type [see below].
A misaligned sample probe, a fourth suggestion, typically causes low
results.
The kit insert allows serum or plasma, and recommends centrifuging at
8-10,000 RCF X 10' for specimens containing 'particulate matter or RBC'.
We have concluded that insufficient centrifugation, especially of
stored/refrigerated specimens, was allowing clots to interfere. We've
increased the speed of our routine separation centrifuges, and added a
repeat spin to the protocol for use of stored/cloudy plasma specimens.
How many labs are routinely pulling 8-10,000 RCF on their separation
centrifuges?
Chris
Dr Chris Lovell-Smith
Chemical Pathologist and Clinical Leader
Healthlab Otago, Dunedin, NZ
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