Free NHA Phlebotomy Procedures and Order of Draw Questions and Answers — Questions and Answers
Question 1: A phlebotomist is preparing to draw blood for coagulation, chemistry, and hematology tests. Which of the following is the correct order of draw?
- Lavender, Light Blue, Green
- Light Blue, Green, Lavender (Correct answer)
- Green, Lavender, Light Blue
- Red, Light Blue, Lavender
Correct answer: Light Blue, Green, Lavender
The correct order of draw is crucial to prevent cross-contamination of additives between tubes. The light blue top tube (sodium citrate) for coagulation tests must be drawn first, followed by tubes for chemistry (like a red or green top), and finally the lavender top tube (EDTA) for hematology.
Question 2: What is the primary function of the additive EDTA found in a lavender-topped tube?
- Promote clot formation
- Inhibit glycolysis
- Bind calcium to prevent clotting (Correct answer)
- Separate serum from cells
Correct answer: Bind calcium to prevent clotting
EDTA (Ethylenediaminetetraacetic acid) is an anticoagulant that works by binding to calcium in the blood. This action prevents the coagulation cascade from proceeding, thus keeping the blood in its whole liquid state for hematology tests.
Question 3: When performing a routine venipuncture, which vein is typically the first choice for the phlebotomist?
- Basilic vein
- Cephalic vein
- Femoral vein
- Median cubital vein (Correct answer)
Correct answer: Median cubital vein
The median cubital vein, located in the antecubital fossa, is the most common site for venipuncture. It is typically large, well-anchored, and less prone to rolling, making it the easiest and safest to access.
Question 4: A patient develops a large, swollen, and bruised area around the venipuncture site. This complication is known as a:
- Hemolysis
- Hematoma (Correct answer)
- Phlebitis
- Petechiae
Correct answer: Hematoma
A hematoma is a collection of blood that has leaked out of the blood vessel and into the surrounding tissue. This can occur if the needle is not fully in the vein or passes through the vein, causing blood to escape.
Question 5: A gray-topped tube is primarily used for which type of laboratory test?
- Coagulation studies
- Complete blood count (CBC)
- Glucose tolerance test (Correct answer)
- Blood cultures
Correct answer: Glucose tolerance test
Gray-topped tubes contain potassium oxalate, an anticoagulant, and sodium fluoride, an antiglycolytic agent. Sodium fluoride prevents the breakdown of glucose by blood cells, making this tube ideal for glucose tolerance tests and other glucose measurements.
Question 6: Which of the following best describes the primary reason for the established order of draw?
- To ensure patient comfort
- To organize tubes by color
- To prevent cross-contamination of additives (Correct answer)
- To fill the largest tubes first
Correct answer: To prevent cross-contamination of additives
The order of draw was established by CLSI to prevent the contamination of non-additive or later-draw tubes by additives from previous tubes. For example, EDTA from a lavender tube can contaminate a green tube and falsely decrease calcium levels.
Free NHA Phlebotomy Procedures and Order of Draw Questions and Answers
A phlebotomist is preparing to draw blood for coagulation, chemistry, and hematology tests.
Which of the following is the correct order of draw?