Which Of The Following Color Tubes Should Be Drawn First

Which Color Tube Should Be Drawn First? A Comprehensive Guide to Phlebotomy Order of Draw

The order of draw in phlebotomy is a critical aspect of blood collection. Following the correct order is paramount to prevent cross-contamination of additives between tubes and ensuring accurate test results. Getting the order wrong can lead to inaccurate lab results, compromising patient care and potentially necessitating repeat venipunctures. This comprehensive guide will delve into the intricacies of the order of draw, explaining the reasons behind it and providing a clear, concise overview for healthcare professionals.

Understanding the Importance of the Order of Draw

The order of draw is a standardized procedure designed to minimize the risk of cross-contamination between different blood collection tubes. Each tube contains various additives, such as anticoagulants, clot activators, or gel separators. These additives can interfere with test results if they contaminate other tubes. For example, an anticoagulant leaking into a tube designed for coagulation studies would render the results useless. Therefore, adhering to the established order of draw is not just a best practice; it’s a crucial step in ensuring the reliability and validity of laboratory test results.

The Standard Order of Draw: A Step-by-Step Breakdown

The universally accepted order of draw is based on the type of additive contained within each tube. While slight variations may exist depending on the specific laboratory or institution, the general principle remains the same. The order prioritizes tubes with no additives, followed by those with clot activators, and finally tubes with anticoagulants. Here’s a detailed breakdown:

1. Blood Culture Bottles (if applicable)

Why first? Blood cultures are collected first to minimize the risk of contamination from other tubes. Bacteria from the skin or other sources could potentially enter the blood sample during the venipuncture process. Collecting the blood culture bottles first helps to reduce this contamination risk. The process usually involves using two bottles – an aerobic and an anaerobic bottle - to cultivate both types of bacteria.

Important Considerations: Thoroughly cleanse the venipuncture site using an appropriate antiseptic to minimize the chances of introducing contaminants.

2. Tube with Clot Activator (Red Top Tube - no additive, Gold/Red Tiger Top Tube - with clot activator and gel separator)

Why Second? After blood cultures, tubes with clot activators are drawn next. These tubes are typically used for serum tests. The clot activator ensures rapid clotting, making serum separation faster and easier. Red top tubes, though technically lacking additives, are often placed before the tiger top because of the likelihood of clotting interfering with the next tubes. The gold/tiger top contains both a clot activator and a gel separator; this gel separates the serum from the blood cells after centrifugation, resulting in a clearer sample.

Important Considerations: Allow sufficient time for complete clotting before centrifugation.

3. Serum Gel Separator Tube (SST) (Gold/Red Tiger Top Tube, sometimes labeled as SST)

Why after the Red Top? As mentioned above, the SST tube contains both a clot activator and a gel separator, promoting efficient clotting and clean serum separation. The gel is inert and prevents cross-contamination between serum and cells following centrifugation.

4. Coagulation Tubes (Light Blue Top Tube - Sodium Citrate)

Why next? Light blue top tubes containing sodium citrate are drawn next. Sodium citrate is an anticoagulant that prevents blood clotting by binding to calcium ions. These tubes are specifically used for coagulation tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT).

Important Considerations: It's crucial to fill the tube completely to maintain the correct blood-to-anticoagulant ratio. Underfilling can lead to inaccurate results.

5. Heparin Tubes (Green Top Tube - Heparin, Light Green Top Tube - Lithium Heparin with Gel Separator)

Why after Coagulation Tubes? Heparin is another anticoagulant, and these tubes are used for plasma testing. Heparin prevents clotting by inhibiting thrombin. Drawing these tubes after coagulation tubes minimizes the risk of heparin contaminating the coagulation samples. Light green tubes with gel separators allow for easy separation of plasma from cells after centrifugation, similar to SST tubes.

Important Considerations: Different types of heparin tubes might exist, each with specific uses and additive concentrations.

6. EDTA Tubes (Lavender/Purple Top Tube - EDTA)

Why after Heparin? EDTA (Ethylenediaminetetraacetic acid) is a chelating anticoagulant that binds to calcium, preventing blood clotting. These tubes are used for hematology testing (e.g., complete blood count - CBC) and other tests requiring whole blood. Drawing them after heparin prevents EDTA contamination of other samples.

Important Considerations: Gently invert the tube several times to ensure proper mixing of the EDTA with the blood.

7. Glycolytic Inhibitors (Gray Top Tube - Sodium Fluoride/Potassium Oxalate)

Why last? Gray top tubes contain additives that prevent glycolysis, the breakdown of glucose. These are used for glucose and other metabolic tests. These are drawn last to avoid contaminating previous tubes.

Important Considerations: It's critical to use the correct amount of additive for accurate blood glucose measurements.

Consequences of Incorrect Order of Draw

Failing to adhere to the correct order of draw can have significant consequences:

• Inaccurate Test Results: Cross-contamination can lead to erroneous results, potentially resulting in misdiagnosis and inappropriate treatment.
• Wasted Resources: Incorrectly collected samples may need to be redrawn, leading to extra costs and time.
• Patient Discomfort: Repeat venipunctures can cause discomfort and potentially lead to complications like hematoma formation.
• Delayed Treatment: Inaccurate results can delay appropriate treatment, which can have serious health implications for the patient.

Beyond the Basics: Situational Considerations

While the standard order of draw provides a solid framework, certain situations may necessitate adjustments. These situations often include:

• Limited Blood Volume: In cases where blood volume is limited (e.g., infants, elderly patients), the phlebotomist might prioritize certain tests and strategically select the order.
• Specific Test Requests: If certain tests have stringent requirements regarding the collection method, these might necessitate deviations from the standard order. Always consult the laboratory's guidelines and individual test requirements.
• Emergency Situations: In emergency situations, the immediate needs of the patient may take precedence. Rapid testing might necessitate prioritizing certain tubes over others.

Conclusion: Mastering the Order of Draw for Accurate and Reliable Results

The order of draw is a crucial aspect of phlebotomy that significantly impacts the accuracy and reliability of laboratory results. Healthcare professionals must be meticulously trained and thoroughly understand the implications of following the correct procedure. By meticulously adhering to the established order of draw and exercising diligence in blood collection practices, healthcare providers can contribute to accurate diagnoses, appropriate treatment, and ultimately, better patient outcomes. Consistent, proper execution of this seemingly simple procedure safeguards the integrity of laboratory results and ensures high-quality patient care. Remember that continual education and adherence to best practices remain vital for maintaining the highest standards in phlebotomy.