Did you know that there is a correct order in which to collect your blood specimens during a venipuncture or cannulation?
This sequence is known as Order of Draw.
Why does it matter?
One problems when filling separate blood collection tubes is that additives contained on one tube may adhere to the needle inserted into the tube and carry-over to subsequent tubes.
This is of particular importance with coagulation tests. Many blood tubes contain anticoagulants or clot activators which would produce erroneous results if they infiltrated the coagulation tube (although in actuality, these effects are probably minimal).
Another problem is that when performing a venipuncture a small amount of tissue fluid may be present in the first-draw specimen. This can produce erroneous readings for some tests.
It is also recommended that when using a winged (butterfly) collection set and the first tube is to be a coagulation (blue) tube, a discard tube should be drawn first. This is expel the air from the butterfly tubing in order to ensure correct blood-to-additive ratio. I have seen some nurses just let the blood flow to the end of the tubing before connecting a collection device.
If using a discard tube it should also be a coagulation tube (for the reasons mentioned above).
What is the order?
Note: if taking blood cultures, these bottles should be filled first. There is also a correct order in which to take blood cultures. More on this here.
Also, it is most important to fill the coagulation tube to the fill line marked on the tube. Again, this is to ensure a correct ratio of blood to additive. Many labs will reject under-filled coags tubes.
Don’t forget to invert.
Finally, don’t forget to invert your tubes once collected to mix any additives.
8–10 times should suffice ( Note: tipping the top down, and then back up again = 1 inversion).
- Effect of Carryover of Clot Activators on Coagulation Tests During Phlebotomy. (n.d.). Retrieved July 1, 2015, from http://ajcp.ascpjournals.org/content/137/6/900.full
- Order of Draw for Multiple Tube Collections – Quest Laboratories. (n.d.). Retrieved July 1, 2015, from http://www.questlabs.com.sg/clinicians/order-of-draw-for-multiple-tube-collections/