Phlebotomy Test Blood Collection Equipment and Supplies 2 — Questions and Answers
Question 1: What additive is found in light blue top tubes and what is its primary use?
- EDTA; for complete blood count
- Sodium citrate; for coagulation studies such as PT and PTT (Correct answer)
- Lithium heparin; for plasma chemistry testing
- Sodium fluoride; for glucose preservation
Correct answer: Sodium citrate; for coagulation studies such as PT and PTT
Light blue tubes contain sodium citrate, which reversibly binds calcium to prevent coagulation; this makes them essential for PT, PTT, and other coagulation studies requiring a precise 9:1 blood-to-additive ratio.
Question 2: Which tube color indicates a plain tube with no additive, used to collect serum by allowing natural clotting?
- Green (lithium heparin)
- Lavender (EDTA)
- Plain red (no additive) (Correct answer)
- Gray (sodium fluoride)
Correct answer: Plain red (no additive)
Plain red top tubes contain no additive, allowing blood to clot naturally so that serum can be separated by centrifugation for chemistry and serology testing.
Question 3: What does SST stand for in phlebotomy, and which color is it typically associated with?
- Standard Serum Tube; red
- Serum Separator Tube; gold or tiger-top (Correct answer)
- Sodium Sulfate Tube; green
- Sterile Specimen Tube; white
Correct answer: Serum Separator Tube; gold or tiger-top
SST stands for Serum Separator Tube; it contains a thixotropic gel and a clot activator, and after centrifugation the gel forms a barrier between serum and the clot for easy serum harvest.
Question 4: How should used phlebotomy needles be disposed of immediately after removal from the patient?
- Recap the needle using the two-handed technique and place in regular trash
- Place directly into an approved sharps container without recapping (Correct answer)
- Bend or break the needle before disposal
- Place in a labeled biohazard bag for later transport to sharps disposal
Correct answer: Place directly into an approved sharps container without recapping
OSHA standards require immediate disposal of used needles into an approved sharps container without recapping, as recapping is the leading cause of needlestick injuries among healthcare workers.
Question 5: What is the required blood-to-additive ratio for a light blue sodium citrate tube to ensure valid coagulation results?
- 1:1
- 4:1
- 9:1 (Correct answer)
- 10:1
Correct answer: 9:1
Light blue tubes must be filled to the correct volume to achieve a 9:1 blood-to-sodium-citrate ratio; underfilling dilutes the sample while overfilling leaves excess anticoagulant, both of which invalidate PT and PTT results.
Question 6: Which additive in gray top tubes inhibits glycolysis to preserve accurate glucose measurements?
- EDTA
- Sodium fluoride (Correct answer)
- Lithium heparin
- Sodium citrate
Correct answer: Sodium fluoride
Sodium fluoride inhibits the glycolytic enzyme enolase, halting cellular consumption of glucose and preserving accurate glucose concentrations for up to 24 hours.
Question 7: What gauge needle is typically used for whole blood donation collection to allow rapid collection of the required volume?
- 25 gauge
- 23 gauge
- 21 gauge
- 16 gauge (Correct answer)
Correct answer: 16 gauge
Blood donation uses a 16-gauge needle to allow approximately 450–500 mL of blood to be collected efficiently within the required timeframe without excessive hemolysis.
Phlebotomy Test Blood Collection Equipment and Supplies 2
What additive is found in light blue top tubes and what is its primary use?