Stability of chemical and immunochemical analytes in uncentrifuged plasma samples.
BACKGROUND
The stability of analyte concentrations in plasma after prolonged contact with blood cells in uncentrifuged lithium-heparin gel tubes was studied.


METHODS
To investigate the stability of concentrations of 26 chemistry and 15 immunochemistry analytes, the simultaneously drawn samples (n = 50) were measured after 6 h storage at +8 degrees C and +22 degrees C in whole blood and after immediate separation of plasma. The analyte concentrations were measured with a Roche Modular PPEE analyser using reagents from Roche Diagnostics.


RESULTS
After prolonged contact with cells a clinically significant change was only observed for potassium where the mean value increased from 4.0 mmol/L to 4.8 mmol/L (P < 0.001) when stored at +8 degrees C.


CONCLUSIONS
Immediate separation of plasma from cells is recommended. However, when prolonged contact of plasma with cell is unavoidable, samples can be kept uncentrifuged for up to 6 h at +8 degrees C or at +22 degrees C. The stability of potassium, however, is temperature-dependent and cannot be measured from refrigerated blood samples.
Leino
Aila
A
TYKSLAB, the Hospital District of Southwest Finland, Turku, Finland. aila.leino@tyks.fi
Koivula
M K
MK
D001685:Biological Factors / Q000097:blood*; D001773:Blood Cells / Q000378:metabolism*; D002498:Centrifugation; D004355:Drug Stability; D007155:Immunologic Factors / Q000097:blood; D010949:Plasma / Q000737:chemistry; D011188:Potassium / Q000097:blood; D013048:Specimen Handling / Q000592:standards*; D013696:Temperature
D001685:Biological Factors; D007155:Immunologic Factors; D011188:Potassium