Veterinary Technician Practice Exam

The green top tube used for blood collection contains lithium heparin as its anticoagulant. Lithium heparin is ideal for various laboratory tests because it prevents blood clotting by inhibiting thrombin, thus allowing for the collection of plasma samples without the formation of clots. This property is particularly useful for tests requiring immediate separation of plasma from blood cells. Lithium heparin is commonly used in clinical settings for chemistry tests, enabling accurate analysis of electrolytes and other substances without the interference that may be caused by clot formation. The quick action of lithium heparin makes it a preferred choice for oncotic tests, veterinary diagnostics, and other laboratory analyses that need fresh samples. In contrast, other anticoagulants like EDTA (used in purple top tubes) are effective for hematology tests but can interfere with certain biochemical assays. Citrate, typically found in light blue top tubes, is mainly used for coagulation studies, while oxalate (found in grey top tubes) is used for glucose testing and can precipitate calcium, which is not suitable for many other types of tests. Thus, the green top tube's use of lithium heparin is specifically tailored for those ample requirements in clinical chemistry.