What is the correct order of draw for blood collection?

The correct order of draw for blood collection is important to prevent cross-contamination of additives from one tube to another, which can affect test results. The standard order begins with tubes that contain no additives, followed by tubes with different types of anticoagulants and additives.

In this case, the sequence of green, lavender, and gray reflects the appropriate protocol. The green tube generally contains lithium heparin or sodium heparin, which is ideal for certain chemistry tests. After that, the lavender tube is used for hematology tests, containing EDTA, an anticoagulant that preserves blood cell morphology. Finally, the gray tube, which typically contains sodium fluoride and potassium oxalate, is used for glucose testing and requires careful ordering to avoid contamination with additives that could skew results.

Choosing this specific order helps ensure that the blood samples maintain their integrity for accurate testing, as each tube's additive serves a different purpose in the analysis. This approach mitigates the risk of erroneous laboratory results resulting from cross-sample contamination.