How does the addition of lithium heparin in a green top tube impact specific tests?
The addition of lithium heparin in a green top tube serves as an anticoagulant, preventing blood clotting by inhibiting the coagulation cascade. This type of tube is commonly used for the collection of plasma specimens for various laboratory tests. Here's how the presence of lithium heparin in a green top tube can impact specific tests:
Role of Lithium Heparin:
Inhibition of Coagulation Cascade:
Lithium heparin acts by binding to antithrombin III, enhancing its inhibitory effect on several coagulation factors. This inhibits the coagulation cascade and prevents the formation of blood clots.
Preservation of Plasma:
The primary purpose of adding lithium heparin is to preserve the blood in a liquid, anticoagulated state, allowing for the collection of plasma.
Compatibility with Plasma Tests:
The use of lithium heparin in green top tubes is well-suited for tests that require plasma specimens. Unlike EDTA or citrate anticoagulants, which are often used for whole blood or platelet studies, lithium heparin allows for the collection of plasma without the need for centrifugation to separate cells.
Compatibility with Chemistry Panels:
Green top tubes with lithium heparin are commonly used for chemistry panels, including liver function tests (e.g., ALT, AST, bilirubin) and kidney function tests (e.g., creatinine).
Measurement of Enzymes:
Lithium heparin is suitable for tests that measure various enzymes present in plasma, as the anticoagulant does not interfere with enzyme activity.
Compatibility with Blood Gas Analysis:
Green top tubes with lithium heparin are used for blood gas analysis, where the preservation of plasma is important for the measurement of gases such as oxygen and carbon dioxide.
Tests Using Green Top Tubes with Lithium Heparin:
Comprehensive Metabolic Panel (CMP):
A panel of tests that includes liver function tests, kidney function tests, electrolytes, and other metabolic markers.
Basic Metabolic Panel (BMP):
A subset of tests within the CMP, focusing on basic metabolic markers.
Liver Function Tests (LFTs):
Tests such as ALT, AST, alkaline phosphatase (ALP), and bilirubin.
Kidney Function Tests:
Tests including creatinine and blood urea nitrogen (BUN).
Electrolyte Panels:
Measurement of electrolytes such as sodium, potassium, and chloride.
Blood Gas Analysis:
Measurement of blood gases, including oxygen and carbon dioxide levels.
Cardiac Enzyme Tests:
Measurement of enzymes such as troponin and creatine kinase-MB (CK-MB).
Pancreatic Enzyme Tests:
Tests measuring pancreatic enzymes such as amylase and lipase.
While lithium heparin in green top tubes is suitable for many chemistry and plasma-based tests, it's important to note that specific tests may have unique anticoagulant requirements. Healthcare professionals should be aware of any special handling or processing requirements specified by the laboratory, as proper sample collection and handling are crucial for obtaining accurate test results.
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