Order Of Draw And Tube Additives In Blood Collection For Laboratory Testing

Summary

• The order of draw is crucial in blood collection to avoid Cross-Contamination and inaccurate results.
• Tube additives play a significant role in preserving blood samples and ensuring accurate Test Results.
• Understanding the relationship between the order of draw and tube additives can improve the quality of blood samples collected.

Introduction

When it comes to blood collection for laboratory testing, there are important guidelines that healthcare professionals must follow to ensure accurate and reliable results. Two critical factors in the blood collection process are the order of draw and tube additives. Understanding the relationship between these two elements is essential for preventing sample contamination and ensuring the integrity of the specimen.

The Order of Draw

The order of draw refers to the sequence in which blood tubes are collected during Venipuncture. Following a specific order helps prevent Anticoagulant contamination between tubes, which can lead to inaccurate Test Results. The order of draw is as follows:

1. Blood Culture tubes
2. Coagulation tubes (Sodium Citrate)
3. Serum tubes (no additives)
4. Heparin tubes
5. EDTA tubes
6. Glycolytic inhibitor tubes

Why is the Order of Draw Important?

Adhering to the proper order of draw is crucial for several reasons:

1. Prevents carryover contamination: When blood collection tubes are filled out of order, additives from one tube can carry over into the next tube, leading to inaccurate Test Results.
2. Ensures Sample Integrity: Following the correct order of draw helps preserve the quality of the blood sample and maintains the stability of the analytes being tested.
3. Reduces pre-analytical errors: By following a standardized order of draw, healthcare professionals can minimize the risk of errors and ensure patient safety.

Tube Additives

Tubes used for blood collection may contain various additives that serve specific purposes. Understanding the role of these additives is essential for selecting the right tubes for specific laboratory tests. Some common tube additives include:

Anticoagulants

Anticoagulants prevent blood from clotting by binding to calcium ions and inhibiting the coagulation cascade. Different anticoagulants are used depending on the type of test being performed:

1. Sodium Citrate: Used for coagulation studies such as PT and PTT.
2. Heparin: Prevents the formation of clots and is used for tests that require plasma samples, such as CBC and electrolyte measurements.
3. EDTA: Binds to calcium ions and is used for tests that require whole blood samples, such as CBC and blood typing.

Preservatives

Preservatives are additives that help maintain the stability of certain analytes in the blood sample. Common preservatives include:

1. Sodium Fluoride: Inhibits glycolysis and is used for tests that require glucose measurement.

Gel Separators

Gel separators are used in serum tubes to create a physical barrier between the serum and the blood cells after centrifugation. This barrier helps prevent cell lysis and ensures accurate Test Results.

Relationship Between the Order of Draw and Tube Additives

The order of draw and tube additives are closely related in the blood collection process. Understanding how these two elements interact is essential for ensuring accurate and reliable Test Results. Here are some key points to consider:

Order of Draw and Anticoagulants

Following the correct order of draw is essential for preventing Cross-Contamination between tubes containing different anticoagulants. For example, if a tube containing EDTA is collected before a Heparin tube, residual EDTA may interfere with coagulation tests and lead to inaccurate results.

Order of Draw and Preservatives

The order of draw also plays a role in preserving analytes that are sensitive to glycolysis. Tubes containing Sodium Fluoride, which inhibits glycolysis, should be collected after serum tubes to prevent interference with glucose testing. Failure to follow the correct order of draw can result in falsely elevated glucose levels due to glycolysis in the sample.

Order of Draw and Gel Separators

Gel separators are commonly used in serum tubes to separate serum from blood cells after centrifugation. Collecting tubes with gel separators out of order can disrupt the barrier created by the gel, leading to cell lysis and potential sample contamination. Following the proper order of draw helps maintain the integrity of the specimen and ensures accurate Test Results.

Conclusion

The relationship between the order of draw and tube additives is crucial in blood collection for laboratory testing. Adhering to the correct order of draw and understanding the role of tube additives helps prevent sample contamination, preserve Specimen Integrity, and ensure accurate Test Results. Healthcare professionals must be knowledgeable about these factors to deliver high-quality care and maintain patient safety.

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