Many of us have experienced this: Every lab in the world has been ordered for your critical patient. In critical situations, our goal is to ensure that we collect blood properly to obtain the most accurate results. If the patient does not have a central line or arterial line, the convenience of blood sampling no longer exists in an emergent situation.
Of course, our worst nightmare is that the lab will call and ask for a redraw because the sample is contaminated or clotted. Several factors come into consideration, including site selection, needle gauge, tourniquet application and release, aseptic technique, gentle inversion of the tubes, and proper labeling. In the midst of the busyness of the situation, we must also remember the order of blood draw.
For some nurses, the order of blood draw is something we can remember easily. For others, we have to refer to our color-coded badge buddy. Of course, thanks to our tube label references, we are grateful that we do not have to memorize which color tube is used for each lab.
The order of blood draw is of the utmost importance because it promotes the accuracy of laboratory results and prevents cross-contamination of additives between blood collection tubes. Adhering to the correct order of draw is essential for maintaining the integrity of blood samples and ensuring patient safety. Although we are aware of this at a basic level, lets take a deeper dive into our nursing responsibilities when drawing blood.
Order of Draw Tube Sequence and Why It Matters
The Clinical and Laboratory Standards Institute (CLSI) is the chief provider of guidelines for the order of draw. Before we dive into the proper sequence, here is a quick history lesson.
If you have been a nurse for over 20 years, you may be aware that the order of draw used to be slightly different. In 2003, the last change in order of draw was made. Previously, serum tube collection preceded light blue top tube collection. At that time, there was also a call for a mass transition from glass blood collection containers to safer plastic tubes. Glass is a natural clot activator, while plastic is not. For this reason, the inside of plastic tubes is coated with a substance to facilitate clotting. As we already know, light blue top tubes are used for coagulation studies. Therefore, the order was changed so that light blue top tubes precede serum tubes.
Below is the current order of draw:
1. Blood Culture Tubes: These are drawn first to prevent contamination from other additives. These are the only tubes/bottles that can be drawn before a light blue top, unless you happen upon a glass non-additive serum tube or a plastic serum tube without a clot activator.
2. Light Blue Top (Sodium Citrate): This tube is used for coagulation tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests. These tubes should be completely filled to maintain the correct blood-to-additive ratio.
3. Red Top (No Additive or Clot Activator): This tube is used for serum tests, including chemistry, electrolytes, cholesterol, thyroid function, liver function, and serology tests. Because there is no additive, the blood can clot naturally.
4. Gold or Tiger Top (Serum Separator Tube - SST): These tubes are similar to the red top tube in that it is used for various chemistry tests. The difference is that it contains a clot activator and a gel separator for faster serum separation. The tiger's top is red-speckled in appearance.
5. Green Top (Lithium Heparin [dark green] or Sodium Heparin [light green]): These tubes are for plasma tests in chemistry. These tests require unclotted, whole blood or plasma (e.g., blood gas analysis, therapeutic drug monitoring, chemistry panels, liver function tests, and some hormone tests). The sodium heparin in the tube inhibits thrombin and other clotting factors. Lithium heparin prevents clotting by binding to thrombin. The tubes must be gently inverted several times after blood collection to make sure the heparin mixes with the blood.
6. Lavender or Pink Top (Ethylenediamine Tetraacetic Acid [EDTA]): These tubes are used for hematology tests such as complete blood count (CBC) and blood bank testing. These tests require whole blood with an anticoagulant. EDTA prevents clotting by binding calcium ions. Pink top tubes are used less commonly than lavender top tubes.
7. Gray Top (Sodium Fluoride/Potassium Oxalate): These tubes are used for glucose testing. Sodium fluoride preserves glucose levels in the sample by inhibiting the glycolysis process.
8. Yellow Top (Acid-Citrate-Dextrose [ACD] Solution): These tubes are used for genetic and tissue typing tests. Some examples are transplantation, deoxyribonucleic acid (DNA) testing, histocompatibility testing, human leukocyte antigen (HLA) phenotyping, blood bank studies, and paternity testing. The ACD solution preserves the viability of cells.
What Scenarios Can Lead to Incidences of Additive Carryover?
The goal of blood culture collection is to ensure that the collection is sterile. For this reason, unlike other collection containers, blood culture bottles are capped. When blood cultures are collected simultaneously with other lab work and not filled first, bacteria from the non-sterile stoppers of the tubes can contaminate the bottles used for blood cultures.
The EDTA from a lavender or pink top tube is potassium-rich. If EDTA carries over into tubes used for chemistry tests (green, red, speckled, or gold-top tubes), the tests may show a falsely elevated potassium level. Imagine being treated for hyperkalemia unnecessarily. Scary thought, right?
If a gold top tube is drawn before a blue top tube, the clot activator from the gold top tube will carry over into the tube. Because the blue top tube is used for coagulation studies, the additive carryover could cause a false shortening of the PT or aPTT. Imagine titrating a continuous heparin infusion based on a false result.
Order of Draw Mnemonics and Memory Tips for Nurses
Some organizations provide badge buddies that serve as a quick reference for the order of blood draw. Some nurses may post the reference on their workstation. Others may opt to laminate the reference and place it right in the tube drawer. Some people create mnemonics or acronyms to remember the order.
The most important thing is to ensure that you are following the guidelines established by your organization. For instance, some less commonly used colors may not be listed above, but may still be used in your organization. According to CLSI, the tube order should take into consideration the potential for the additive in each tube to alter results obtained from the next tube if carryover were to occur.
Along with many other factors, the correct order of draw is vital in ensuring accurate laboratory results and preventing cross-contamination of additives. The responsibility for safe blood sampling no longer belongs solely to the phlebotomist. Nurses are increasingly being upskilled to share the responsibility, as the demand for lab draws often exceeds the bandwidth of phlebotomy staff. I encourage you to be diligent in every aspect of blood sampling and to hold each other accountable in the name of patient safety. I wish you all the best!
About the Author:
With over 20 years of healthcare experience, Karen has been a registered nurse for 16 years. Her direct patient care background is critical care, with 6 years of experience in the medical intensive care unit. She is Master's-prepared in Nursing Education through Towson University with 14 years of nursing education experience. A portion of her nursing education experience was in the university setting as a clinical instructor, clinical practicum nursing instructor, lecturer, and lab instructor. Her current work and most of her nursing education experience have occurred in the hospital setting, facilitating nursing and interdisciplinary education as a systemwide Nursing Professional Development Specialist II, certified by the American Nurse Credentialing Center (ANCC).
Karen is a published scholarly nursing journal corresponding author, blogger, and continuing education course writer. She is also a certified trainer for Crisis Prevention Institutes Nonviolent Crisis Intervention with Advanced Physical Skills and Johns Hopkins Activity & Mobility Promotion (JH-AMP). In addition, she is a member of the American Nurses Association, the Maryland Nurses Association, the Delaware Organization of Nurse Leaders, the Association of Nursing Professional Development, and the American Association of Critical Care Nurses (AACN).
Karen is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely those of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your healthcare provider for any health-related questions or concerns.
If you want to learn more about CEUfast's Nursing Blog Program or would like to submit a blog post for consideration, please visit https://ceufast.com/blog/submissions.
