Potassium is released from the platelets on clotting and therefore the potassium level would be higher - especially if the patient had a raised platelet level.
The situation can be demonstrated in a heparinised sample with a high platelet count. If you reduce the centrifugation speed and time by half - you wil produce platelet rich plasma and this will give a raised potassium result complared to the correctly spun sample.
A correctly spun heparinised sample will consist of clear plasma over packed red cells with a distict white buffy layer between.
"We tortured the data until it confessed."
Trevor Walmsley, Canterbury Health Labs, Christchurch, New Zealand.
Phone: (0064 3) 364 0326 Fax:Phone: (0064 3) 364 0320
eMail: [log in to unmask]
Internet: http://www.cdhb.govt.nz/chlabs/staff/trevorw.htm
>>> Keith Lewis <[log in to unmask]> 13/3/02 1:03 am >>>
We recently had a report from the ITU where the nurse obtained an heparinised blood specimen for blood gas analysis. Whatever the reason, at the same time another specimen was sent to the lab as a clotted specimen. Measurement of potassium on the ABL 725 blood gas analyser gave a result of 3.4 mmol/L, the potassium result on our analyser in the lab gave a result of 5.2 mmol/L. These findings were duplicated on several occasions, but only on one particular patient ! The usual causes were ruled out. When heparinised blood was sent to the lab as suggested we obtained the same result has on the ABL blood gas analyser. It was then found out that the patient had a very raised platelet count.
Keith Lewis
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