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Phlebotomy is more than the skill of drawing blood or acquiring different specimens. It is an important procedure to determine specific aspects of patient health the physicians need to know in order to treat their patient. “Phlebotomy, which dates back to the age of ancient Greece, has gained experience through the evolution of medicine becoming a fundamental diagnostic tool.” (Ialongo, C., 2016). In order to obtain a variety of specimens, it is crucial to preform phlebotomy procedures safely and effectively. A phlebotomist needs to be well trained in their scope of practice and be well educated in all aspects of phlebotomy. Knowing the tubes being used and in what order to use them in is part of the knowledge needed to be a phlebotomist.
When obtaining a patient’s blood, it is significant to draw in the correct order of draw. Each tube has specific additives and these additives can affect certain tests. If blood is drawn in the wrong order of tubes, the blood collected can be contaminated. This will exhibit improper values for the tests being done on that tube. This comes back to patient safety, because the patient may get an improper diagnosis or treatment that can harm them. The correct order of draw and tube colors are blood cultures (anaerobic and aerobic), light blue, red-clear, red, red-black tiger or gold, light green, green, gray-green tiger, lavender, pink, tan, royal blue, and gray. It is important to know this order because patients will need a specific amount of tubes drawn, per the doctors orders, and the phlebotomist needs to order them correctly.
The lavender tube comes ninth in the order of draw and is a very common tube for phlebotomists to use. It is crucial to draw a lavender tube after all the previous colors have been drawn. This will ensure the additives have not contaminated future specimens. The additive in the lavender (purple) topped tube is ethylenediamenetetraacetic acid or abbreviated to EDTA. Inside the tube wall is coated with K2EDTA or K3EDTA. The K2 and K3 represent the form of potassium in the tube. “The EDTA can be ordered as K2 (spray-dried potassium) attached to EDTA or K3 (liquid potassium) attached to EDTA.” (Garza, D., 2015). This additive is also a coagulant, which is important for certain tests the lavender topped tube is used for.
The common tests for each tube depend on the additives that are in each tube. For the lavender tube, the common tests are complete blood count (CBC), hemoglobin and hematocrit (H&H), red blood count (RBC), white blood count (WBC), platelet count, WBC differential count, erythrocyte sedimentation rate (ESR), sickle cell screening, HGB A1-C, mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and mean cell volume (MCV). Some other tests used with this tube are molecular diagnostic testing, immunology, and hemoglobin A1-C. The additives in this tube, K2 and K3, are important for certain types of tests. For hematology tests like CBC and RBC, the additive K2 is better to use. For viral markers it is better to use the K3 additive. (Garza, D., 2015).
Most tubes have special considerations which are actions that need to be taken for that specimen and additive. The lavender tube does not have many special considerations, but like all tubes, need to be filled with the correct amount of blood, need to be inverted the proper amount of times, and used in the correct order of draw. However, if the lavender tube is not mixed properly with 8 inversions, micro clots may form. Mixing the sample to much or violently may cause hemolysis. An interesting fact about the lavender tube is that it can also be used for blood donor screening like the pink topped tube.
Each tube has a specified amount of blood the vacuumed pressure of the tube will allow. The lavender topped tubes can hold 2.0 mL, 3.0 mL, 5.0 mL or 0.75 mL depending on the size of the tube. “To assure proper ratio of EDTA to blood, it is recommended that the tubes contain no less than one-half of the stated volume.” (Department of Pathology, 2019). Over or under filling a tube can cause errors in the test results because of the improper ratio between blood and additive. Under filling the lavender topped tube can cause false low blood counts, low hematocrits, blood smears, and morphologic changes to red blood counts. “Insufficient sample volumes produce relatively elevated EDTA levels, which can increase the chelation of magnesium and zinc, and can then affect reagent enzymes used for signal generation, such as alkaline phosphatase.” (Bowen, R. A., 2014).
To properly mix the blood sample for the lavender topped tube, the tube is inverted 8 times. Gently inverting the sample will mix the correctly mix the additive with the blood. It is also important to not break the blood cells and mix the sample quickly to avoid micro clots. Each tube will vary slightly on the amount of inversion needed to mix the sample. As part of staying educated on all the tubes and tools for a blood draw, the phlebotomist should be aware of each tubes inversions.
A phlebotomist has numerous responsibilities that include the patient’s safety, staying educated, and preforming their skills effectively. Knowing each tube will ensure the phlebotomist will carry out all of their responsibilities. The phlebotomist must know the additives, the tests that tube is used for, any special considerations that tube may have, the volume of blood that needs to be in the tube, how many inversions the tube needs to properly mix the blood and additives, and where in the order of draw the tube needs to be. “Tubes are drawn in a specific order to avoid the possibility of erroneous test results caused by carryover of an additive.” (Mohammed, S., 2013). If one or any of these aspects about the tubes are not done properly, the test results will be flawed. When the test results are off, the patient is in danger of a false diagnosis or treatment options.
- Bowen, R. A., & Remaley, A. T. (2014, February 15). Interferences from blood collection tube components on clinical chemistry assays. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936985/
- Garza, D., Becan-McBride, K., Hermis, D., & Lockett, P. S. (2015). Phlebotomy handbook: Blood specimen collection from basic to advanced. London: Pearson.
- Ialongo, C., & Bernardini, S. (2016, February 15). Phlebotomy, a bridge between laboratory and patient. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783087/
- Mohammed, S., & JB, A. A. (2013, June 02). Effects of Blood Collection Tubes on Determination Vitamin-A by HPLC. Retrieved from https://www.omicsonline.org/effects-of-blood-collection-tubes-on-determination-vitamin-a-by-hplc-2157-7064.1000184.php?aid=14520&view=mobile
- Department of Pathology and Laboratory Medicine. University of California, Irvine- School of Medicine. Specimen Requirements/Containers. (2019, January 25). Retrieved from http://www.pathology.uci.edu/services/specimen-containers.asp
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