What do EDTA, Lithium Heparin, and Sodium Citrate have in common?

The correct answer is that EDTA, Lithium Heparin, and Sodium Citrate are all anticoagulants. These substances are utilized in laboratory settings to prevent blood from clotting, allowing for the analysis of blood components without interference from coagulation. Each anticoagulant works by a different mechanism: EDTA binds calcium ions, which are essential for the clotting process, while Lithium Heparin enhances the activity of antithrombin III, and Sodium Citrate also binds calcium.

These anticoagulants are critical in various blood tests, particularly those assessing coagulation parameters or complete blood counts, as they ensure that the sample remains in a liquid state, which is necessary for accurate analysis. The other options do not apply here; for example, promoting clotting and being used for serum samples are characteristics of substances that facilitate coagulation, rather than prevent it, and not all of them are found in red top tubes since red top tubes typically do not contain any additives, allowing for clot formation.