Final answer:
A phlebotomist seeking to obtain serum should use a serum separator tube (SST) that typically contains a clot activator and separator gel. The clot activator allows blood to clot, and after centrifugation, the gel separates the serum from the clotted blood, ready for testing.
Step-by-step explanation:
For a phlebotomist with a requisition for tests on a patient's serum, the correct collection tube typically contains either a clot activator or none at all to allow the blood to clot, and a separator gel. These tubes are often referred to as serum separator tubes (SST). When blood is placed in these tubes, the clot activator helps the blood to clot, and the separator gel forms a physical barrier between the serum and the clotted blood after centrifugation. This allows for the serum to be easily collected for the tests specified on the requisition form.
The presence of the clot activator ensures that, over the period of typically 30 minutes to one hour, the blood will clot, and separation can be achieved through centrifugation. In the scenario where the technician collects the blood sample and an hour later harvests the serum, this indicates that during the hour, the blood had time to clot and subsequently, the sample was likely centrifuged to separate the serum from the clotted components. This serum is then used for various diagnostic tests.
It is important to select the correct tube with the right additive as per the test requirements. For serum-based tests, a tube with no additive or a clot activator and gel for serum separation is appropriate.