The Function of Additives in Venous Blood Collection Tubes: A Guide for Phlebotomists

Summary

• Additives in venous blood collection tubes play a crucial role in preserving blood samples and ensuring accurate Test Results.
• These additives prevent blood clotting, preserve cellular components, and maintain the integrity of the sample during transportation and storage.
• Understanding the function of additives in venous blood collection tubes is essential for phlebotomists to ensure the quality of blood samples for laboratory testing.

Phlebotomy is the practice of drawing blood from patients for laboratory testing, diagnostics, or blood transfusions. In the process of venous blood collection, phlebotomists use specialized tubes with various additives to preserve the integrity of blood samples and ensure accurate Test Results. These additives serve specific functions in maintaining the quality of the sample and preventing changes that could affect diagnostic outcomes. In this article, we will explore the function of additives in venous blood collection tubes in phlebotomy.

Anticoagulants

One of the essential additives in venous blood collection tubes is anticoagulants. These substances prevent blood clotting by inhibiting coagulation factors, thus ensuring that the blood sample remains in a liquid state. Clotting can interfere with laboratory tests by affecting the composition of the sample and leading to inaccurate results. Different types of anticoagulants are used depending on the tests being performed and the laboratory protocols in place.

Common anticoagulants used in venous blood collection tubes include:

1. Ethylenediaminetetraacetic acid (EDTA): EDTA is a chelating agent that binds calcium ions, which are necessary for the coagulation cascade. It is commonly used for hematology tests that require whole blood samples.
2. Heparin: Heparin inhibits the action of thrombin, a key enzyme in the blood clotting process. It is often used for biochemistry and coagulation tests.
3. Sodium Citrate: Sodium Citrate binds calcium ions and is used for coagulation studies to assess the clotting ability of the blood.

Preservatives

In addition to anticoagulants, venous blood collection tubes may contain preservatives to maintain the stability of certain analytes in the sample. These preservatives prevent degradation or changes in the composition of the blood components, ensuring accurate Test Results. Some common preservatives used in blood collection tubes include:

1. Borates: Borates are used to stabilize enzymes and prevent their degradation in plasma samples for biochemistry tests.
2. Fluorides: Fluorides inhibit glycolysis, the breakdown of glucose, in blood samples, enabling accurate measurements of glucose levels in plasma or serum.
3. Acids: Acids such as citric acid or acetic acid are used to lower the pH of the sample, preventing the degradation of certain analytes and stabilizing the sample for analysis.

Separation Gel

Some venous blood collection tubes are equipped with a gel separator that forms a barrier between the serum or plasma and the cells in the sample. This gel acts as a physical barrier during the centrifugation process, allowing for the separation of serum or plasma from cellular components. After centrifugation, the serum or plasma can be easily extracted from the top of the tube without contamination from the cellular fraction below.

The use of a separation gel in blood collection tubes is particularly important for tests that require serum or plasma samples free of cellular components, such as certain chemistry tests or serological assays. By preventing mixing between the serum or plasma and cells, the separation gel ensures the accuracy and reliability of Test Results.

Conclusion

Understanding the function of additives in venous blood collection tubes is crucial for phlebotomists to ensure the quality and integrity of blood samples for laboratory testing. Anticoagulants prevent blood clotting, preservatives maintain the stability of analytes, and separation gels facilitate the isolation of serum or plasma from cellular components. By using the appropriate tubes with the right additives, phlebotomists can help to ensure accurate and reliable Test Results for patient diagnosis and treatment.

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