Final answer:
A phlebotomist centrifuges a serum specimen before sending it to a reference lab to separate the serum from the cells. This process ensures specimen purity and prevents cellular contamination that could interfere with diagnostic tests. Centrifugation is a standard protocol in sample preparation for various laboratory analyses.
Step-by-step explanation:
A phlebotomist should centrifuge a serum specimen before transport to an outside reference laboratory to separate the serum from the blood cells. During centrifugation at high rotations, typically 3000 rpm or higher, the denser components like red blood cells and platelets move to the bottom of the tube, allowing the clear, cell-free serum to be collected from the top. Serum is the liquid portion of blood that remains after clotting has occurred and it lacks clotting factors unlike plasma. The separation process ensures that the reference laboratory receives a specimen that is not contaminated by cells, which could interfere with diagnostic tests and compromise the accuracy of results.
In the provided examples, blood samples containing anticoagulants like lithium heparin or K2EDTA were centrifuged to obtain plasma, whereas for serum production, no anticoagulants are used and the blood is allowed to clot first before centrifugation. Centrifuging samples is a crucial step in laboratory protocols, whether preparing samples for analyses, such as blood glucose levels, or for more complex procedures like cross matching blood types for transfusions. Pretreatment of samples, like quenching plasma with methanol, may also be done to stabilize them for accurate analysis.