Order of Draw Explained: Clearing Out Any Confusion
Phlebotomy is not just about drawing blood. It also covers proper care and handling of the specimen that will be used for laboratory testing or analysis. It is vital that the samples are not contaminated or tainted in any way, and should be handled in such a way that quality and accuracy of the analysis is not compromised. Special considerations must also be applied when collecting indwelling catheter line draw and blood cultures. This is where the order of draw becomes necessary.
To avoid cross-contamination of additives between tubes, blood must be drawn in a specific order. The procedure is the same for all types of tubes or instruments used. It is vital that the order is followed not only to avoid contamination, but also to ensure accuracy of test results. Because the smallest error could mean that the patient might not receive the most appropriate care and treatment for his specific case.
Who determines the order of draw?
Formerly known as the National Commission of Clinical Laboratory Standards (NCCLS), the Clinical Laboratory Standards Institute (CLSI) (http://clsi.org/) approves and publishes the order of draw. Since the procedure can change if new research indicates probable inaccuracy in a test result, it is important that health care and testing facilities use the most recent order of draw. The latest update is the H3-A6 from November 2007 that is also used by several laboratory accreditation agencies, including The Joint Commission and the College of American Pathologist.
What is the recommended order?
The same order is used for glass and plastic venous blood collection tubes, evacuated system and a syringe. There used to be a separate order for blood collected using a syringe, but it has been rendered obsolete as research showed there was no reason to use a different order.
Before getting to the order of draw, familiarizing certain acronyms will make the entire process simpler and easier to understand.
SPS – Sodium polyanethole sulfonate
SST – Serum Separator Tube
EDTA – ethylenediaminetetraacetic acid
FDP – Fibrin degradation products
Order of Draw as Recommended by CLSI (http://188.8.131.52/NewsLetter.pdf)
- Yellow – SPS (Blood culture)
Blood cultures are used in microbiology. The additive it uses is a broth mixture that is intended to preserve the quality of microorganisms.
- Light Blue – Sodium Citrate
Coagulation tubes have light blue-colored stopper and a sodium citrate additive. It is used for coagulation tests, requiring full draw.
- Plain Red – No Additive
This is commonly used for routine venipuncture and does not require any additive.
- Plastic Red – Clot Activator
Tubes with plastic red stoppers contain a clot activator. It causes blood clots and help in separating the serum by centrifugation. This process is often used in blood bank (cross-match), chemistry, immunology and serology.
- Gold, Red/Gray – SST/Gel w/Clot Activator
Serum separator tube (SST) does not have any additive but a clot activator that will separate blood from the serum by centrifugation. This draw is used in chemistry, immunology and serology.
- Green – Heparin-Lithium or Sodium
Tubes with green tops have lithium heparin anticoagulant.
- Lavender, Purple, Tall Pink – EDTA
The EDTA anticoagulant in tubes with lavender or purple stopper helps remove calcium by forming calcium salts. This draw is often used in blood bank cross-matching and hematology.
- Gray – Sodium Fluoride, Potassium Oxalate
Tubes with gray-colored stopper contain sodium fluoride or potassium oxalate additives, which acts as an Antiglycolytic agent that helps preserve glucose for up to five days. This requires full draw, as the opposite may cause hemolysis.
Aside from these, there is a tube with royal blue top that contains FDP. The draw is used when there is an order to test deep vein thrombosis or blood clot in a deep vein, pulmonary embolism, stroke and other blood clotting disorders. If a patient shows any symptom related to the condition, royal blue draw will be requested.
Order of Draw for Skin Puncture
Skin puncture specimens have to be collected according to a certain order as recommended by CLSI, which is as follows:
- Lavender (EDTA) micro-collection tube
- Plasma additive micro-collection tubes, such as green (lithium heparin) light green (lithium heparin with gel), gray (sodium fluoride and potassium oxalate)
- Serum micro-collection tubes, such as red (no additive), gold (clot activator and gel)
This is to ensure that specimens requiring anticoagulants are drawn first. Whenever clot appears in a micro-collection tube with a lavender stopper/shield, the specimen will be rejected. An added precaution is to never use iodine or Betadine solutions to cleanse the skin before collecting blood samples to prevent possible interference of test results, especially in the analysis of potassium, glucose, and total protein.
Why must the order of draw be followed accordingly?
As already mentioned, this is done to avoid cross-contamination and unreliable test results. How can this happen?
A tube with EDTA, for example, is rich in potassium and can cause an increase in potassium levels. Therefore, if a test for potassium is required, the tubes used must be those that are placed before those that contain EDTA. The same thing is true when a coagulation test need to be performed. Since tubes with clot activators can interfere with the results, tubes with light blue stopper or shield must be used before those that have red/gray stopper, gray/yellow stopper, gold shield, red shield and orange shield tubes.
Blood culture tubes are usually at the top of the order of draw to avoid contamination of the blood collected. This is because bacteria from non-sterile tube stoppers or shields may result in bacteria growth, which will show in the test result as a blood infection. This is why blood culture bottles or SPS tubes with yellow stopper must be collected first before any other tubes.
How do you remember the order of draw?
Considering the number of colored stoppers or shields to remember, mistakes are bound to happen. Since there is no room for error in phlebotomy, it is crucial that you memorize the order in the easiest way possible. A very helpful mnemonics has been developed — Sally brings really good grease and leaves the gravy.
Brings – Blue
Really – Red
Good – Gold
Grease (and) – Green
Leaves (the) – Lavender
Gravy – Gray
Using this mnemonics, remembering the order of draw would be easier. There are also products in the market that are designed to aid phlebotomists in their jobs, such as a bracelet that is colored according to the draw specified.
Be aware, however, that certain tubes are made for research purposes only. The order of draw in this case is according to manufacturer’s instruction. When you switch from research to actual venipuncture, it is important that you are able to differentiate one task from another.
Color codes may also differ in certain laboratories and you should always verify before you draw any blood. It is the responsibility of a laboratory to determine the type of specimen to be collected based on various factors, such as manufacturer’s recommendation, analytical method and type of analyzer used. For STAT testing, for example, some labs may use a tube with a green top since the test can be done on plasma and can be centrifuged right after it was received. This eliminates the time spent on waiting for a specimen to clot.
There is the CLSI-recommended order of draw and there are steps specified by a laboratory. It is important to verify which order you should follow wherever you are assigned as a phlebotomist.