NHI Phlebotomy and Lab Procedures 2 — Questions and Answers
Question 1: Which additive in a lavender-top tube prevents clotting by binding calcium?
- Sodium citrate
- Heparin
- EDTA (Correct answer)
- Sodium fluoride
Correct answer: EDTA
EDTA (ethylenediaminetetraacetic acid) chelates calcium ions to prevent coagulation in lavender-top tubes.
Question 2: A patient's arm shows a hematoma forming during venipuncture. What is the FIRST action?
- Apply a warm compress
- Release the tourniquet and remove the needle (Correct answer)
- Redirect the needle to a different angle
- Increase suction on the evacuated tube
Correct answer: Release the tourniquet and remove the needle
When a hematoma forms, the phlebotomist must immediately release the tourniquet and remove the needle to stop blood from leaking into surrounding tissue.
Question 3: Which vein is considered the FIRST choice for routine venipuncture in adults?
- Basilic vein
- Cephalic vein
- Median cubital vein (Correct answer)
- Dorsal hand vein
Correct answer: Median cubital vein
The median cubital vein is preferred because it is large, well-anchored, and usually close to the surface with minimal nerves nearby.
Question 4: What is the purpose of the 'order of draw' in phlebotomy?
- To speed up specimen processing time
- To prevent cross-contamination of additives between tubes (Correct answer)
- To ensure proper labeling sequence
- To reduce patient discomfort during collection
Correct answer: To prevent cross-contamination of additives between tubes
The order of draw minimizes carryover of tube additives into subsequent tubes, which could interfere with test results.
Question 5: A gray-top tube contains sodium fluoride. What is its PRIMARY purpose?
- Preserve coagulation factors
- Inhibit glycolysis to preserve glucose levels (Correct answer)
- Promote clot formation
- Prevent hemolysis of red cells
Correct answer: Inhibit glycolysis to preserve glucose levels
Sodium fluoride inhibits glycolytic enzymes, preventing red blood cells from consuming glucose and ensuring accurate glucose measurements.
Question 6: Which condition results from excessive tourniquet pressure or prolonged application?
- Hemodilution
- Hemoconcentration (Correct answer)
- Hemolysis
- Lipemia
Correct answer: Hemoconcentration
Prolonged tourniquet application causes fluid to shift out of vessels, concentrating cellular components and analytes — a condition called hemoconcentration.
Question 7: In the context of chain of custody, which specimen type typically requires this strict documentation?
- Routine CBC
- Drug-of-abuse urine specimen (Correct answer)
- Basic metabolic panel
- Thyroid function test
Correct answer: Drug-of-abuse urine specimen
Drug-of-abuse specimens require chain of custody documentation to ensure specimen integrity and legal defensibility of results.
NHI Phlebotomy and Lab Procedures 2
Which additive in a lavender-top tube prevents clotting by binding calcium?