What is the function of anticoagulants in green top tubes?

Anticoagulants in green top tubes serve the primary function of preventing blood from clotting. The green top tubes contain sodium heparin or lithium heparin, which are both effective anticoagulants. Their presence allows for the collection of plasma, which is used in various laboratory tests that require the analysis of blood components without the interference of clotted cells. This is particularly important in tests that need accurate measurement of substances such as electrolytes or certain hormones.

The other options do not accurately represent the role of anticoagulants in green top tubes. Making a blood sample sterile relates more to collection techniques rather than the function of anticoagulants. Enhancing glucose testing is not a function of the anticoagulants themselves, and while preserving the sample for longer periods is a consideration in sample handling, it is not directly attributable to the role of anticoagulants like those found in green top tubes. Thus, the correct answer highlights the essential role of anticoagulants in maintaining the integrity of blood samples for testing.