Did you know that phlebotomy is one of the oldest forms of medicine? Thousands of years ago, as far back as the Egyptians and perhaps even further, “physicians” would draw blood (this was called blood-letting) for the perceived medical benefits. Today their methods seem foolish and barbaric but at the time, they were on the cutting edge of medicine.
Today, drawing blood is one of the most common medical procedures worldwide with hundreds of millions, if not billions, of samples of blood being drawn every year. As with all medicine, processes change as new information becomes available and drawing blood is no different. These procedures have changed to accommodate for advances in blood medicine and upgrades in medical technology, such as the transition to plastic tubes as opposed to glass tubes.
What is the Order of Draw and Why is it Important?
The order of draw was designed to protect against contamination in the blood samples that are drawn. An internationally recognized and uniform process is the elegant solution that was designed to tackle this significant challenge.
What exactly is it? It is the precise order in which the specimens are to be drawn from the patient and which labeled tubes these samples are to be drawn into. Why is it important? If the order of draw is not followed, there is a chance that there could be additive carryover from one tube to the other and this could alter the lab results. This can have incredibly significant consequences.
Is it important to follow this order? Absolutely it is. While there are some situations in which the order of draw may be different, understanding the standard order of draw is critical in phlebotomy training and practice. What is this order of draw?
The Order of Draw: The Process
First thing first, always make sure that the documentation for your patients matches and is accurate. This ensures that after the specimens are tested, the results are given to the right people. For these results to be accurate and reduce the risk of contamination, follow this order.
- Blood culture tubes
This is a specimen that is meant for the culture of microorganisms for the recovery of potential pathogens.
- Sodium citrate tubes (e.g., blue-stopper)
This tube and its blood specimen are for coagulation tests.
- Serum tubes with or without clot activator, with or without gel separator (e.g., red-, gold-, speckled-stopper)
The serum is what is left after the blood clots. It is a cell-free liquid that has no coagulation factors. Many tests are done on this serum to measure lipids, electrolytes, hormones etc.
- Heparin tubes with or without gel (e.g., green-stopper)
This “heparinized blood is used for special whole blood tests, among other uses.
- EDTA tubes (e.g., lavender-stopper)
These tubes use EDTA as a coagulant and are preferred for molecular tests.
- Glycolytic inhibitor tubes (e.g., grey-stopper)
Also known as potassium oxalate/sodium fluoride tubes they use potassium oxalate as a coagulant and sodium fluoride as a preservative. These are used to preserve glucose in the blood and are helpful for other special chemistry tests.
The Order of Draw Can Have Exceptions
As with almost all medical procedures, there can be exceptions to the rule. What it comes down to are the policy and trust. In certain situations, the order of draw may be different and if the policy suggests that it should be drawn in a different order, after making sure you understand why, always follow the policy.