Phlebotomy Test Phlebotomy Exam Simulation 1 — Questions and Answers
Question 1: A physician orders a prothrombin time (PT/INR). Which tube is collected FIRST if no other tubes are being drawn?
- Lavender top (EDTA)
- Light blue top (sodium citrate) (Correct answer)
- Gold top (SST)
- Green top (heparin)
Correct answer: Light blue top (sodium citrate)
Sodium citrate tubes for coagulation tests must be the first tube collected (after a discard tube in some protocols) to avoid EDTA or additive contamination that would interfere with coagulation testing.
The established order of draw for venipuncture (per CLSI H3-A6/GP41) is: (1) Blood culture bottles (if ordered); (2) Sodium citrate (light blue) — coagulation studies. When collecting only a coagulation tube, a discard tube of the same type (sodium citrate) is sometimes recommended before it to avoid the first drops of blood that may contain tissue thromboplastin (which could activate coagulation factors and alter PT results)—however, current CLSI guidance indicates a discard tube is not required if the collection is clean with a straight-stick, though some facilities still require it; (3) Serum tubes (gold, red, SST); (4) Heparin tubes (green); (5) EDTA tubes (lavender, pink); (6) Other additive tubes (gray). The critical reason for citrate first (without blood cultures) is that additives from other tubes can contaminate citrate samples—EDTA carryover particularly interferes with coagulation factor activity.
Question 2: During venipuncture, the needle bevel should be positioned:
- Downward (facing the skin surface)
- Upward (facing away from the skin) (Correct answer)
- At a 90-degree angle to the vein
- Parallel to the patient's arm regardless of bevel position
Correct answer: Upward (facing away from the skin)
The needle bevel must be up (facing the ceiling) so the sharp cutting edge enters the vein cleanly and blood enters the needle without the bevel edge cutting the vessel wall.
The bevel of a needle is the angled cut at the tip that creates the sharp point for penetration. Correct venipuncture technique requires the bevel facing up (away from the skin/toward the ceiling) for several reasons: (1) The sharp edge enters the vein wall cleanly, causing minimal trauma; (2) The opening of the bevel faces into the vessel lumen, allowing blood to flow efficiently into the needle; (3) Bevel-down would place the sharp cutting edge against the inner wall of the vein, increasing the risk of laceration, digging into the opposite vessel wall (trans-fixation), and causing hematoma; (4) Blood flow into a bevel-down needle is also less efficient as the opening may be partially against the vessel wall. The bevel-up position is standard for all venipuncture procedures, confirmed visually before insertion by ensuring the orientation marking on the needle hub corresponds to the bevel.
Question 3: A patient identifies themselves, but the name on the tube label doesn't match the requisition. The phlebotomist should:
- Draw the blood using the tube that's already labeled and correct it later
- Stop the procedure and resolve the discrepancy before drawing blood (Correct answer)
- Draw the blood and inform the nurse after collection
- Use the name the patient stated and cross out the label name
Correct answer: Stop the procedure and resolve the discrepancy before drawing blood
Any patient identification discrepancy must be resolved BEFORE drawing blood; collecting on a mislabeled specimen is a serious patient safety error that can cause wrong-patient results.
Patient identification is the single most critical step in phlebotomy and the most common source of wrong-patient laboratory errors. CLSI GP47 and TJC National Patient Safety Goals require at least two independent patient identifiers (name and date of birth being most common) be verified with the patient (not from a room sign or chart) and matched to the requisition/labels before any specimen is collected. If ANY discrepancy exists—name spelling, date of birth, identifier number—the phlebotomist must STOP and resolve the discrepancy before proceeding. Actions: check the patient's armband, verify with nursing staff, re-check the requisition, contact the laboratory or ordering provider. Drawing blood with a known ID mismatch and planning to correct it afterward is never acceptable, as the specimen is compromised and could result in a wrong-patient result if the correction is not made properly. This is a never event.
Question 4: Which of the following represents the CORRECT order of draw for a patient requiring a CBC, BMP, and INR?
- Lavender → Light blue → Gold
- Light blue → Gold → Lavender (Correct answer)
- Gold → Lavender → Light blue
- Lavender → Gold → Light blue
Correct answer: Light blue → Gold → Lavender
The correct order is light blue (sodium citrate/INR) first, then gold (SST/BMP) second, then lavender (EDTA/CBC) last, following the established CLSI order of draw.
CLSI order of draw for this combination: (1) Light blue (sodium citrate) — for INR/PT/coagulation; must be first because EDTA contamination (from lavender) would chelate calcium needed for the coagulation cascade, falsely prolonging PT and invalidating INR. (2) Gold top (SST) — serum separator tube for BMP (metabolic panel); clot activator and gel separator; collected after citrate so tissue thromboplastin from the first puncture doesn't affect coagulation. (3) Lavender top (EDTA) — for CBC; EDTA chelates calcium and anticoagulates; collected last among these three because EDTA carryover into serum or citrate tubes is most damaging. This sequence is critical: if EDTA were collected before the SST, trace EDTA on the needle tip could contaminate the SST and cause calcium to be falsely low, potassium falsely elevated, and multiple enzyme values to be affected.
Question 5: A tourniquet should be released:
- Only after the needle is removed from the vein
- As soon as blood begins flowing into the collection tube (Correct answer)
- After all tubes have been filled and the needle is removed
- After 3 minutes to ensure adequate venous filling
Correct answer: As soon as blood begins flowing into the collection tube
The tourniquet should be released as soon as blood flow is established (within 1 minute of application) to prevent hemoconcentration and altered test results from prolonged venous occlusion.
Tourniquet application causes localized venous congestion, which over time concentrates non-filterable substances in the stasis blood: large proteins, red blood cells, and non-diffusible analytes increase in concentration while fluid shifts out of capillaries. This hemoconcentration effect becomes significant after approximately 1 minute and causes falsely elevated results for: total protein, albumin, bilirubin, cholesterol, hematocrit, hemoglobin, potassium, and calcium. CLSI guidelines specify: (1) Apply the tourniquet no more than 1 minute before collection; (2) Release the tourniquet AS SOON AS blood begins flowing into the first collection tube; (3) If a tourniquet must be reapplied (failed first attempt), allow 2 minutes for blood to normalize before reapplying. Never leave a tourniquet on for the entire multi-tube collection—release after the first tube fills, or immediately upon needle insertion if blood flows well.
Question 6: Which personal protective equipment (PPE) is REQUIRED for routine venipuncture?
- Gloves only (Correct answer)
- Gloves and mask
- Gloves, gown, and face shield for all routine draws
- Gloves and eye protection for all routine draws
Correct answer: Gloves only
OSHA's Bloodborne Pathogens Standard requires gloves for all routine venipuncture; additional PPE (mask, gown, face shield) is added based on the splash/exposure risk of the specific procedure.
OSHA's Bloodborne Pathogens Standard (29 CFR 1910.1030) requires appropriate personal protective equipment to protect healthcare workers from exposure to blood and body fluids. For routine venipuncture: (1) Gloves are ALWAYS required—they provide a barrier against contact with blood; (2) Mask and eye protection are added when there is a risk of splash, spray, or spatter of blood or body fluids—this applies during certain procedures but is not required for every routine draw; (3) Gowns are added when contamination of clothing is likely. Specific situations requiring full PPE: arterial blood gas collection (risk of blood spray during de-capping), blood culture collection, patients with active bleeding, collection of large volumes, and certain precaution-level patients (contact, droplet, or airborne precautions may require gown, mask, or N95 in addition to gloves). Gloves must be changed between patients; hands must be washed with soap and water or sanitized with hand sanitizer before and after gloving.
Question 7: A phlebotomist experiences a needlestick injury after blood collection. What is the FIRST action to take?
- Complete the remaining specimen collection first, then report the injury
- Immediately wash the wound with soap and water and report the exposure per facility protocol (Correct answer)
- Apply a bandage and notify the supervisor at the end of the shift
- Squeeze the wound to express blood and apply antiseptic
Correct answer: Immediately wash the wound with soap and water and report the exposure per facility protocol
Immediate wound washing with soap and water is the first response to needlestick injury, followed by immediate reporting per facility exposure control plan.
The correct response to a needlestick or sharps injury, per OSHA Bloodborne Pathogens Standard and CDC guidelines: (1) IMMEDIATELY wash the wound thoroughly with soap and water for several minutes; do NOT squeeze the wound (squeezing may increase exposure) and do NOT use bleach or caustic chemicals; (2) For mucous membrane exposure: flush eyes/mouth with large amounts of water; (3) IMMEDIATELY report the exposure to the supervisor and employee health/occupational health department—do not wait until end of shift; (4) Document the incident per the facility's exposure control plan (source patient, type of needle, depth of injury, PPE worn, immediate actions taken); (5) Receive post-exposure evaluation including source patient HIV/HBV/HCV status if available and consent obtained; (6) Consider post-exposure prophylaxis (PEP) for HIV if indicated—PEP must be started within 2 hours of exposure for maximum effectiveness; (7) Follow up with occupational health for testing and monitoring. Completing the blood draw before addressing the injury is NEVER acceptable.
Question 8: Which blood tube additive is used to inhibit glycolysis and preserve glucose concentration in the specimen?
- EDTA
- Sodium heparin
- Sodium fluoride (Correct answer)
- Sodium citrate
Correct answer: Sodium fluoride
Sodium fluoride inhibits the enzyme enolase in the glycolytic pathway, preventing cells from metabolizing glucose after collection and preserving the glucose concentration in the specimen.
Sodium fluoride (NaF), found in gray-top tubes (typically combined with potassium oxalate as an anticoagulant), is the standard additive used for glucose specimen preservation. It acts as a glycolysis inhibitor by blocking enolase, an enzyme in the glycolytic pathway. Without inhibition, red blood cells, white blood cells, and platelets continue to metabolize glucose after specimen collection at approximately 5–7 mg/dL/hour at room temperature. Gray-top tubes maintain glucose stability for 24–48 hours at room temperature (3 days refrigerated). EDTA anticoagulates for hematology but does not prevent glycolysis—glucose falls in EDTA tubes at room temperature. Heparin anticoagulates but also does not inhibit glycolysis. Sodium citrate prevents coagulation for coagulation studies. For routine stat glucose testing where the specimen will be analyzed immediately, plasma from a heparin tube or serum from SST is acceptable; gray-top is critical when processing is delayed.
Phlebotomy Test Phlebotomy Exam Simulation 1
A physician orders a prothrombin time (PT/INR).
Which tube is collected FIRST if no other tubes are being drawn?