American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

When collecting blood with a syringe, what is the proper order to place samples into evacuated tubes?

1. Lavender, Blue, Red

2. Red, Blue, Lavender

3. Blue, Lavender, Red

4. Blue, Red, Lavender

The correct answer is: Blue, Lavender, Red

The correct sequence to place blood samples into evacuated tubes is dictated by the type of additive present in each tube and the potential for cross-contamination. The appropriate order starts with the blue-top tube, which contains sodium citrate, used primarily for coagulation studies. Following this, the red-top tube is next; it is usually without additives and can be used for serum tests. Finally, the lavender-top tube, which contains EDTA as an anticoagulant, is placed last. This order helps to prevent any contamination of the blood samples from additives that could interfere with test results, such as the anticoagulants in EDTA. By placing the blue tube first, any citrate from the blue tube will not affect the coagulation studies, and since the red tube does not have any additives, placing it before the lavender tube ensures that the serum obtained does not interact with the anticoagulants in the lavender tube. The incorrect sequences fail to maintain optimal sample integrity, which is critical for accurate testing results in a clinical setting.