Phlebotomy Technician

Answer: D - PST stands for “plasma separator tubes”. These tubes usually have green-gray or light green colored tops. The inside of a PST tube is coated with either sodium heparin, lithium heparin, or ammonium heparin. Always check which additive is inside the PST, before using. A PST with a lithium coating is not appropriate for a lithium level, as the lithium will increase the results. A PST tube also has a gel barrier at the bottom of tube that moves upward during centrifuge, separating the plasma from the whole blood.