What additive is found in a green top blood collection tube?

The green top blood collection tube contains lithium heparin, which is an anticoagulant that prevents blood from clotting. Lithium heparin works by inhibiting the action of thrombin, an enzyme that plays a crucial role in the clotting process. This characteristic makes the green top tube particularly useful for various plasma chemistry tests, as it allows for the collection of plasma samples without clot formation.

Understanding the application of different tubes is essential for veterinary practice, as using the correct additive ensures the integrity of the sample for accurate laboratory results. Other tubes mentioned in the options—such as those containing EDTA, which is used in purple top tubes for hematology tests, and sodium citrate, found in light blue top tubes for coagulation studies—serve different purposes in the collection and processing of blood samples. Therefore, recognizing the specific additive associated with each tube color is critical for proper sample collection and handling.