NHA Phlebotomy Certification Practice Exam

What is the correct order of draw for blood collection tubes?

1. Red, light blue, lavender, green

2. Light blue, green, lavender, red

3. Red, lavender, green, light blue

4. Green, lavender, light blue, red

The correct answer is: Red, light blue, lavender, green

The correct order of draw for blood collection tubes is essential to prevent cross-contamination of additives between tubes, which can affect test results. Starting with the red tube, it is used for serum testing and has no additives, making it a suitable first choice as it does not introduce any substances that could interfere with the tests performed in subsequent tubes. Following the red tube is the light blue tube, which contains sodium citrate for coagulation studies. This tube must be drawn after the red to ensure that no other additives interfere with the citrated samples. Next in line is the lavender tube, which contains EDTA, an anticoagulant used for hematology tests including complete blood counts. It is important that this tube follows the light blue tube to maintain the integrity of the anticoagulant properties. Finally, the green tube, which can contain heparin, is drawn last. By this point in the collection process, any potential contaminants from the previous tubes will not affect the heparin's effectiveness. This sequence—red, light blue, lavender, and green—ensures that each additive in the tubes does not contaminate subsequent samples, leading to more accurate test results. Understanding this order is crucial for anyone involved in blood collection and laboratory processes.