What is the purpose of adding an anticoagulant to evacuated tubes?

The purpose of adding an anticoagulant to evacuated tubes is to prevent the blood from clotting. Anticoagulants work by inhibiting various components of the coagulation pathway, which allows for the collection of whole blood or plasma for accurate laboratory testing. Clot formation would lead to the separation of serum from the cellular components, complicating the analysis and potentially skewing results.

In clinical practice, the choice of anticoagulant can also depend on the type of tests being performed; for example, EDTA is commonly used for hematology tests as it binds calcium ions, which are necessary for blood clotting.

The other options focus on aspects that do not align with the primary purpose of anticoagulants. They might dilute the sample or ensure sterility, but these functions do not relate directly to the need to prevent coagulation.