Avoiding Errors: Learn the Correct Order of Blood Draw

If you’ve ever had your blood drawn for a blood test before, you might have noticed the phlebotomist selecting specific tubes in a particular sequence. This process is known as the order of draw, and it’s more than just a routine—it’s an important protocol to ensure accurate laboratory results.

But what exactly is the correct order of blood draw, and why does it matter?

Why the Order of Draw is Important

The primary reason for adhering to the correct order of draw is to avoid cross-contamination between additives in blood collection tubes. Each tube is designed for a specific test and contains an additive such as an anticoagulant or clot activator. If these additives mix due to improper sequencing, it can lead to erroneous test results, potentially impacting patient diagnosis and treatment.

Cross-contamination can occur when residual additives from one tube mix with blood in another tube. For example:

• If EDTA from a lavender-stopper tube, which contains high levels of potassium, contaminates a tube intended for potassium testing (such as green-, red-, gold-, or speckled-top tubes), it can artificially elevate potassium levels, potentially causing serious medical errors.
• If a clot activator from another tube contaminates a blue-stopper tube used for coagulation studies, it may falsely shorten the prothrombin time (PT) or activated partial thromboplastin time (aPTT).
• If blood cultures are not collected first during simultaneous lab work, bacteria from the non-sterile stoppers of other tubes may contaminate the blood culture bottles.

Following the order of draw minimizes these risks and ensures the integrity of the sample.

The Standard Order of Draw

To minimize cross-contamination among samples, CLSI has established guidelines for the correct order of draw. Follow this order whether you are using a syringe or vacutainer. Here’s the standard sequence:

1. Blood Culture Tubes (Yellow or Yellow-Black Top)
   • Purpose: Used for microbiological tests to detect infections in the bloodstream.
   • Rationale: These tubes are sterile and drawn first to prevent contamination from additives in other tubes. Any contamination could compromise the ability to accurately identify pathogens.
2. Coagulation Tubes (Light Blue Top)
   • Purpose: Used for coagulation studies such as prothrombin time (PT) and activated partial thromboplastin time (aPTT).
   • Rationale: The sodium citrate additive in these tubes can be affected by contamination, so they’re drawn immediately after blood cultures. Accurate coagulation results are vital for diagnosing clotting disorders.
3. Serum Tubes (Red Top or Gold Top)
   • Purpose: Used for tests requiring serum, such as chemistry panels and serology.
   • Rationale: These tubes contain no additives (red top) or clot activators and gel separators (gold top) that should not interact with anticoagulants from other tubes. Proper order ensures the separation of serum for accurate testing.
4. Heparin Tubes (Green Top)
   • Purpose: Used for plasma determinations in chemistry tests.
   • Rationale: These tubes contain lithium or sodium heparin, which could interfere with other tube additives if drawn earlier. Heparin prevents clotting, making it ideal for certain chemistry analyses.
5. EDTA Tubes (Lavender or Pink Top)
   • Purpose: Used for hematology tests like complete blood count (CBC) and blood typing.
   • Rationale: EDTA is a strong anticoagulant and could interfere with potassium levels and other tests if drawn out of order. Its anticoagulant properties are essential for preserving cellular morphology in hematology.
6. Oxalate/Fluoride Tubes (Gray Top)
   • Purpose: Used for glucose and lactate testing.
   • Rationale: These tubes contain potassium oxalate and sodium fluoride, which can significantly affect other test results if cross-contamination occurs. Sodium fluoride preserves glucose levels by inhibiting glycolysis.

What is the Order of Draw by Tube Color?

If you are wanting the order of tube color, here’s a quick reference for the tube colors in the correct sequence:

1. Yellow or Yellow-Black (Blood Culture)
2. Light Blue (Coagulation Studies)
3. Red or Gold (Serum Tests)
4. Green (Heparin)
5. Lavender or Pink (EDTA)
6. Gray (Oxalate/Fluoride)

How to Remember the Order of Draw

For phlebotomists and nurses who are sort of new to the profession forgetting the order of draw may happen sometimes. However, you don’t want to forget the order of draw and collect blood in the wrong order. If that happens you can always ask a fellow phlebotomist nearby.

To remember the order of draw though, many use mnemonics. One popular one is:

• Your Brother Runs Good Laps Greatly.
  • Yellow, Blue, Red, Green, Lavender, Gray.

You can use that one, or you can create your own mnemonic that’s easy for you to recall! Some phlebotomists prefer to visualize the tubes and their corresponding tests to help them remember. Whatever works for you is okay just ensure that you are following the correct order.

Best Practices for Drawing Blood

• Stay Updated: Always confirm the order of draw with the latest CLSI guidelines and facility protocols.
• Mix Properly: Ensure proper mixing of tubes by gentle inversion (avoid vigorous shaking to prevent hemolysis).
• Label Immediately: Label each tube immediately after drawing to avoid mix-ups.
• Organize Supplies: Arrange tubes in order before the procedure to streamline the process and minimize errors.

Exceptions and Special Cases

In some cases, special protocols may override the standard order of draw. For instance:

• Winged infusion sets (butterfly needles): When using these, a discard tube may be required to eliminate air from the tubing before collecting a light blue top tube. This step ensures the proper blood-to-additive ratio.
• Patient-specific requirements: Certain tests or conditions may necessitate deviations from the typical sequence. For example, if a test requires immediate analysis, its corresponding tube may take precedence.
• Pediatric Draws: In pediatric patients, the volume of blood collected may influence the sequence to prioritize essential tests.

Common Phlebotomy Errors and How to Avoid Them

1. Mixing Tubes Incorrectly: Failing to follow the correct order can lead to contaminated samples and inaccurate results. Always double-check the sequence.
2. Insufficient Sample Volume: Underfilling tubes can compromise test accuracy. Use the correct technique to ensure adequate blood collection.
3. Hemolysis: Vigorous shaking or improper handling can cause red blood cells to rupture, affecting test outcomes. Handle samples with care.

Conclusion

It is very important to follow the order of draw when drawing blood. If you are new to the profession, use mnemonics or some other creative idea to help you remember the order.

If you forget, don’t be afraid to ask another phlebotomist or nurse. If you make a mistake don’t hesitate to redo the collection. It’s critical that the order of draw is always followed to prevent cross contamination and ensure the best results.

So, remember it’s the Yellow or Yellow-Black (Blood Culture) first, then Light Blue (Coagulation Studies), Red or Gold (Serum Tests), Green (Heparin), Lavender or Pink (EDTA), and Gray (Oxalate/Fluoride).