The acellular fluid component of blood in which the cells are suspended. Plasma differs from serum in that plasma still contains clotting factors, whereas serum is processed from clotted blood in which the clotting factors have been consumed.
It practical terms, plasma has to be collected in tubes that contain an anti-coagulant, such as heparin. Centrifugation of the sample results in the cellular component at the end of the tube, while the less dense, straw-coloured plasma remains at the top of the tube as the supernatant. Plasma and serum can be used interchangeably for some tests, but in some assays, the anti-coagulant can interfere with analysis.
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