Which tube contains lithium heparin and a gel separator?

The PST, or Plasma Separation Tube, is the correct answer because it is specifically designed to contain lithium heparin as the anticoagulant and a gel separator. Lithium heparin is an effective anticoagulant that prevents blood clotting during the collection and handling process, allowing for the testing of plasma or whole blood. The gel separator aids in the separation of plasma from the cellular components of the blood after centrifugation, facilitating easier sample processing and analysis.

Other tubes, such as the gray tube, typically contain additives like sodium fluoride and potassium oxalate, which serve to preserve glucose levels but do not include lithium heparin or a gel separator. The pink tube is primarily used for blood banking and contains EDTA as an anticoagulant, while the SST, or Serum Separation Tube, often contains a different type of gel separator and typically collects serum rather than plasma. The distinct combination of lithium heparin and a gel separator in the PST tube makes it ideal for specific plasma tests.