Phlebotomy Technician Certification
Tubes and additives: practice questions
Our Phlebotomy bank has 18 questions on this topic. Here are 4 of them with answers; the full mock exam draws from every topic, like the real one.
Question 1
Which tests usually use a light blue-top tube?
- CBC
- PT/INR and aPTT (coagulation tests)
- Lipid panel and fasting glucose tests
- Glucose
Show the answer
B. PT/INR and aPTT (coagulation tests) — The tube must be filled correctly for the 9:1 ratio.
Question 2
How many times should a light blue-top tube be gently inverted?
- 20 times
- 3–4 times
- Not at all
- 8–10 times
Show the answer
B. 3–4 times — Inversion counts follow the manufacturer's instructions.
Question 3
Which tube contains a clot activator and gel separator?
- Light blue (sodium citrate), used for coagulation studies
- Gray
- Gold or tiger-top serum separator tube (SST)
- Lavender
Show the answer
C. Gold or tiger-top serum separator tube (SST) — Gel separates serum from cells after centrifugation.
Question 4
What is the blood-to-anticoagulant ratio in a light blue-top tube?
- 1:1
- 4:1
- 9:1
- 20:1
Show the answer
C. 9:1 — Underfilled tubes give falsely prolonged results.