NHI Phlebotomy and Lab Procedures 5 — Questions and Answers
Question 1: Which tube additive is found in a green-top tube and is used for plasma chemistry tests?
- EDTA
- Sodium citrate
- Heparin (Correct answer)
- Sodium fluoride
Correct answer: Heparin
Green-top tubes contain heparin (lithium or sodium heparin), which inhibits thrombin and is used when plasma is needed for chemistry testing.
Question 2: What is the MAXIMUM recommended time a tourniquet should remain applied during venipuncture?
- 30 seconds
- 1 minute (Correct answer)
- 2 minutes
- 5 minutes
Correct answer: 1 minute
Tourniquets should not remain applied for more than 1 minute to prevent hemoconcentration and alteration of analyte levels.
Question 3: A patient has an IV line running in the left antecubital fossa. Where should the phlebotomist collect blood?
- Below the IV site in the same arm
- From the right arm or a site distal to the IV in the same arm (Correct answer)
- Directly from the IV tubing
- From the same arm above the IV site
Correct answer: From the right arm or a site distal to the IV in the same arm
Blood should be drawn from the opposite arm or distal to the IV to avoid IV fluid contamination of the specimen.
Question 4: When collecting a specimen for a PKU (phenylketonuria) neonatal screen, what collection method is used?
- Venipuncture into a lavender tube
- Heel stick onto a filter paper card (Correct answer)
- Urine catheterization
- Arterial blood gas via radial puncture
Correct answer: Heel stick onto a filter paper card
Neonatal PKU screens use capillary blood from a heel stick applied directly to specific circles on a filter paper (Guthrie card).
Question 5: What term describes the clear, yellowish fluid that remains after blood has clotted and the clot is removed?
- Plasma
- Serum (Correct answer)
- Buffy coat
- Filtrate
Correct answer: Serum
Serum is the liquid portion of blood after clotting; unlike plasma, it lacks fibrinogen and other clotting factors consumed in the clot.
Question 6: Which of the following BEST describes the 'butterfly' or winged infusion set?
- A large-bore needle used for rapid transfusion
- A small-gauge needle with flexible tubing used for difficult veins (Correct answer)
- A device for arterial blood gas collection only
- A syringe system used exclusively for pediatric heel sticks
Correct answer: A small-gauge needle with flexible tubing used for difficult veins
Butterfly needles (winged infusion sets) have small gauges and flexible tubing, making them ideal for fragile, small, or difficult veins such as in elderly or pediatric patients.
Question 7: After venipuncture, gauze is applied and the patient bends their arm to hold pressure. Why is bending the arm discouraged by many guidelines?
- It restricts blood return to the heart
- It can increase bruising and hematoma formation at the puncture site (Correct answer)
- It causes the specimen tube to clot prematurely
- It dislodges the tube label
Correct answer: It can increase bruising and hematoma formation at the puncture site
Bending the arm can reopen the puncture site or increase venous pressure, promoting hematoma formation; direct pressure with the arm extended is preferred.
NHI Phlebotomy and Lab Procedures 5
Which tube additive is found in a green-top tube and is used for plasma chemistry tests?