Question 1

Which of the following statements best explains why vacuum tubes must be filled to the indicated volume line during blood collection?

Accepted Answer

To ensure the correct blood-to-additive ratio and prevent erroneous test results.

Question 2

A patient requires a STAT serum potassium test. Which tube should be used to obtain the fastest serum separation?

Accepted Answer

Orange-topped tube with thrombin-based clot activator.

Question 3

Which additive is most appropriate for collecting blood for a complete blood count (CBC) and why?

Accepted Answer

EDTA, because it prevents platelet aggregation and preserves cell morphology.

Question 4

A phlebotomist is preparing to collect blood for a prothrombin time (PT) test. Which tube should be selected and why?

Accepted Answer

Light-blue–topped tube, because it contains sodium citrate for coagulation studies.

Question 5

Which of the following best describes the mechanism by which oxalates, citrates, and EDTA prevent blood clotting?

Accepted Answer

They remove calcium by forming insoluble calcium salts.

Question 6

A blood specimen for glucose testing is delayed in processing. Which tube additive best preserves glucose levels in the sample?

Accepted Answer

Sodium fluoride, because it inhibits glycolysis.

Question 7

Which of the following is a critical safety practice when using needles for blood collection?

Accepted Answer

Immediately discarding used needles in a rigid, leak-proof sharps container.

Question 8

A laboratory receives a blood sample in a green-topped tube. For which of the following tests is this sample LEAST appropriate?

Accepted Answer

Blood smear for Wright’s stain.

Question 9

Why should tourniquets used in blood collection be cleaned with a 1:10 bleach solution if contaminated with blood?

Accepted Answer

To disinfect and prevent transmission of blood-borne pathogens.

Question 10

Which of the following is a real-world consequence of using an expired vacuum tube for blood collection?

Accepted Answer

The tube may not fill to the required volume, resulting in an incorrect blood-to-additive ratio.

Question 11

A phlebotomist is collecting blood for lead testing. Which tube should be used and what is its additive?

Accepted Answer

Tan-topped tube containing EDTA.

Question 12

Which of the following best describes the function of the polymer barrier in serum separation tubes?

Accepted Answer

It forms a barrier between serum and cells during centrifugation.

Question 13

A blood culture is ordered for a patient suspected of septicemia. Which additive is most appropriate and why?

Accepted Answer

Sodium polyanethol sulfonate (SPS), because it inhibits phagocytosis and reduces antibiotic activity.

Question 14

Which of the following is a key reason for using gloves during blood collection?

Accepted Answer

To protect both the patient and the phlebotomist from exposure to blood-borne pathogens.

Question 15

A phlebotomist is preparing to collect blood from an infant. What is the recommended maximum penetration depth for a heel stick and why?

Accepted Answer

Less than 2.0 mm, to avoid penetrating the bone.

Question 16

Which of the following best explains why blood collection tubes with EDTA should not be used for calcium testing?

Accepted Answer

EDTA binds calcium, making it unavailable for measurement.

Question 17

A laboratory is conducting a nutritional study requiring trace element analysis. Which tube is most appropriate for this purpose?

Accepted Answer

Royal-blue–topped tube.

Question 18

Which of the following is a plausible reason for a vacuum tube failing to fill with blood during venipuncture?

Accepted Answer

The tube has lost its vacuum due to expiration or improper storage.

Question 19

A phlebotomist is using a butterfly needle for blood collection. What is a primary advantage of this device?

Accepted Answer

It is ideal for patients with small or fragile veins.

Question 20

Which of the following substances can interfere with clinical testing of blood analytes if present in the collection tube?

Accepted Answer

Talcum powder from gloves.

Blood Collection Equipment and Additives: Principles and Applications in Microbiology and Clinical Laboratory Science

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