CCMA Phlebotomy and Specimen Collection 2 — Questions and Answers

Question 1: Which tube color is used when collecting a sample for a complete blood count (CBC)?

Red top (no additive)
Gold/SST (serum separator)
Lavender/purple top (EDTA) (Correct answer)
Light blue top (sodium citrate)

Correct answer: Lavender/purple top (EDTA)

The lavender/purple top tube contains EDTA (ethylenediaminetetraacetic acid), which preserves blood cell morphology and is required for CBC testing.

Lavender/purple top tubes contain EDTA (K2 or K3 EDTA), which chelates calcium ions to prevent clotting. This preserves red and white blood cells and platelets in their native state, making it the standard tube for hematology tests including CBC, differential, reticulocyte count, and HbA1c. Red/gold tops are used for chemistry panels; light blue tops for coagulation studies (PT/PTT); green tops for chemistry panels requiring heparinized plasma.

Question 2: What is the purpose of releasing the tourniquet before withdrawing the needle during venipuncture?

To increase blood flow for a larger sample volume
To prevent a hematoma from forming at the puncture site (Correct answer)
To slow the blood draw for accurate measurement
To maintain the vein for additional draws

Correct answer: To prevent a hematoma from forming at the puncture site

Releasing the tourniquet before withdrawing the needle prevents blood from continuing to flow under pressure into surrounding tissues, which would cause a hematoma.

The tourniquet must be released before withdrawing the needle (or at least within 1 minute of application) to: (1) prevent hematoma formation caused by blood forced into surrounding tissue under pressure, (2) prevent hemolysis, (3) prevent falsely elevated results for potassium and other analytes affected by prolonged venous stasis. After releasing the tourniquet, apply gauze to the site, withdraw the needle, and apply pressure immediately.

Question 3: Which of the following veins is most commonly used for routine venipuncture?

Cephalic vein
Median cubital vein (Correct answer)
Basilic vein
Femoral vein

Correct answer: Median cubital vein

The median cubital vein in the antecubital fossa is the preferred site for venipuncture due to its size, stability, and accessibility.

The antecubital fossa is the primary area for venipuncture, with three veins available: the median cubital (most preferred — central, large, stable, less likely to roll), the cephalic (lateral, used second choice), and the basilic (medial, last choice due to proximity to the brachial artery and median nerve). The femoral vein is used only in emergencies by qualified personnel and is not an appropriate site for routine phlebotomy.

Question 4: A fasting blood glucose specimen must be collected after the patient has fasted for at least:

2 hours
4 hours
8 hours (Correct answer)
24 hours

Correct answer: 8 hours

A fasting blood glucose requires a minimum 8-hour fast (no food or caloric beverages) to ensure baseline glucose levels unaffected by recent food intake.

A fasting blood glucose requires 8–12 hours of fasting (water is allowed). Fasting ensures that glucose levels reflect the body's baseline state and are not elevated from recent food intake. Normal fasting glucose is 70–99 mg/dL; 100–125 mg/dL indicates prediabetes; ≥126 mg/dL on two separate occasions indicates diabetes. Other fasting labs include lipid panels (9–12 hour fast) and glucose tolerance tests. Medical assistants must verify fasting status before collection.

Question 5: What does 'hemolysis' mean in the context of blood specimen collection?

Clotting of the blood sample in an anticoagulated tube
Destruction of red blood cells releasing intracellular contents (Correct answer)
Separation of serum from clotted blood
Contamination of the sample with bacteria

Correct answer: Destruction of red blood cells releasing intracellular contents

Hemolysis is the rupture or destruction of red blood cells, releasing their contents (especially potassium and hemoglobin) into the serum, which can interfere with many lab tests.

Hemolysis occurs when red blood cell membranes break down, releasing intracellular contents — particularly potassium, LDH, and hemoglobin — into the plasma or serum. The sample appears pink to red. Causes include: using too small a needle (shear force), excessive syringe suction, vigorous shaking, prolonged tourniquet time, and drawing through a butterfly in a small vein. Hemolysis can falsely elevate potassium, AST, LDH, and phosphorus, causing specimen rejection and requiring recollection.

Question 6: When using a syringe for venipuncture, which of the following is the correct step after withdrawing blood?

Immediately shake the syringe to prevent clotting
Transfer blood into collection tubes using a blood transfer device (Correct answer)
Recap the needle and store for later transfer
Inject blood directly into tubes through the rubber stopper using the syringe needle

Correct answer: Transfer blood into collection tubes using a blood transfer device

Blood drawn via syringe must be transferred into collection tubes using a safety blood transfer device to maintain specimen quality and prevent needlestick injuries.

After syringe venipuncture, blood must be transferred into vacutainer tubes using a Luer-lock blood transfer device (a needleless adapter that attaches to the syringe and allows safe tube engagement). Never manually push the plunger rapidly (causes hemolysis), never recap the needle, and never use the syringe needle to puncture the tube stopper (risk of needlestick, hemolysis, aerosol). Fill tubes in the correct order (same as ETS order of draw), allow vacuum to pull blood naturally.

CCMA Phlebotomy and Specimen Collection 2

Which tube color is used when collecting a sample for a complete blood count (CBC)?