23 Venipuncture Procedure & Complications Practice Questions & Answers

1. 1. A phlebotomist collects the following tubes in this order: light blue (sodium citrate), lavender (EDTA), green (lithium heparin), gray (sodium fluoride/potassium oxalate). Which statement identifies the error?

   • A.The gray tube should have been collected before the lavender tube.
   • B.The light blue tube should have been collected after all serum and plasma tubes.
   • C.The lavender EDTA tube should have been collected after the green heparin tube.✓ Answer
   • D.The order was correct as performed; color sequence does not matter when no serum tube is ordered.

   The CLSI venous order of draw is blood culture, light blue citrate, serum (red/gold/SST), green heparin, lavender EDTA, then gray fluoride/oxalate. Heparin must precede EDTA because EDTA carryover contaminates later tubes and distorts chemistry results; the sequence exists to prevent additive carryover, not for convenience.

   Source: CLSI PRE02-Ed8, order of draw for venous collection (blood culture → citrate → serum → heparin → EDTA → fluoride/oxalate); NHA CPT Domain 3, task "follow order of draw"Report a problem with this question

2. 2. Carryover of EDTA from a lavender tube into a chemistry tube drawn afterward will most likely produce which result change?

   • A.No change, because EDTA is inert in chemistry testing
   • B.Falsely increased glucose with no other effect
   • C.Falsely increased potassium and falsely decreased calcium✓ Answer
   • D.Falsely decreased potassium and falsely increased calcium

   EDTA is supplied as a potassium salt (K2/K3EDTA) and works by chelating calcium, so carryover adds potassium to the specimen while binding calcium; it also falsely lowers alkaline phosphatase and iron. This is the mechanism the order of draw is designed to prevent.

   Source: CLSI PRE02-Ed8, additive carryover rationale for order of draw; NHA CPT Domain 3 knowledge statement on tube additivesReport a problem with this question

3. 3. A phlebotomist must collect only a PT/INR (light blue sodium citrate tube) using a winged (butterfly) collection set. What should be done first?

   • A.Use a 25-gauge needle so the tube fills more slowly
   • B.Draw a discard tube to fill the dead air space in the tubing✓ Answer
   • C.Deliberately fill the citrate tube only to about 60% of its stated volume
   • D.Draw a lavender EDTA tube first to prime the line

   The tubing of a winged set holds air; if the citrate tube is drawn first, that air displaces blood and the tube underfills, ruining the required 9:1 blood-to-anticoagulant ratio. A discard tube (non-additive or another coagulation tube) primes the line and need not be filled completely.

   Source: CLSI PRE02-Ed8, discard tube required when a citrate tube is the first tube drawn with a winged set; 9:1 fill ratio requirementReport a problem with this question

4. 4. Which tube may be drawn immediately before a light blue sodium citrate tube without compromising coagulation results?

   • A.A lavender-top EDTA tube
   • B.A plastic serum tube containing no clot activator✓ Answer
   • C.A green-top lithium heparin tube
   • D.A gold-top SST containing clot activator and separator gel

   CLSI permits only blood culture bottles, glass non-additive serum tubes, or plastic serum tubes without clot activator to precede the citrate tube. Clot activator, heparin, and EDTA carryover all interfere with the clotting cascade and falsely alter PT/aPTT.

   Source: CLSI PRE02-Ed8, tubes permitted before the citrate tube in the order of drawReport a problem with this question

5. 5. Which sequence is correct for a capillary (dermal puncture) collection?

   • A.Blood gas → serum → EDTA → other additive tubes
   • B.Serum tubes → other additive tubes → EDTA → blood gas
   • C.Blood gas → EDTA → other additive tubes → serum✓ Answer
   • D.EDTA → blood gas → serum → other additive tubes

   The capillary order differs from the venous order: blood gas first to limit air exposure, then EDTA, because platelets begin clumping at the puncture site within moments and a delayed EDTA sample yields falsely low platelet counts. Serum tubes are collected last.

   Source: CLSI GP42, capillary order of draw (blood gas, EDTA, other additive, serum)Report a problem with this question

6. 6. A light blue sodium citrate tube is filled to roughly 60% of its stated volume. What is the consequence?

   • A.The tube is acceptable if it is inverted 8 to 10 times instead of 3 to 4
   • B.PT and aPTT will be falsely shortened but remain reportable
   • C.Only the hematocrit is affected; coagulation results are unchanged
   • D.PT and aPTT will be falsely prolonged, so the specimen must be rejected and recollected✓ Answer

   Citrate tubes require at least 90% of the stated fill because the liquid anticoagulant is pre-measured for a 9:1 ratio. Excess citrate relative to plasma binds additional calcium in the test system, artificially prolonging clotting times.

   Source: CLSI PRE02-Ed8, minimum 90% fill requirement for sodium citrate tubesReport a problem with this question

7. 7. How should a lavender-top EDTA tube be handled immediately after it is removed from the tube holder?

   • A.No mixing is needed; EDTA is a dry additive that dissolves on its own
   • B.Invert it gently 3 to 4 times, the same as a citrate tube
   • C.Invert it gently 8 to 10 times through a full 180-degree turn✓ Answer
   • D.Shake it vigorously 3 to 4 times to dissolve the additive quickly

   EDTA requires 8 to 10 gentle 180-degree inversions so the anticoagulant contacts all the blood; inadequate mixing produces microclots that make a CBC unacceptable, while shaking ruptures red cells and causes hemolysis.

   Source: CLSI PRE02-Ed8, manufacturer-specified tube inversion requirements (EDTA 8–10 inversions)Report a problem with this question

8. 8. During a venipuncture in the antecubital fossa, the patient suddenly reports a sharp, electric, shooting pain radiating into the thumb. Which action should the phlebotomist take FIRST?

   • A.Loosen the tourniquet and quickly finish the remaining tubes
   • B.Reposition the needle slightly and continue the draw
   • C.Reassure the patient that this sensation is normal and hold the needle still
   • D.Remove the needle immediately and discontinue the draw✓ Answer

   Sharp, electric, radiating pain or numbness signals nerve involvement, and any further needle movement can convert a transient injury into permanent damage such as complex regional pain syndrome. The needle is withdrawn at once, the draw is stopped, and the event is reported and documented.

   Source: CLSI PRE02-Ed8 Chapter 4, nerve injury response; NHA CPT Domain 3, recognize and respond to complicationsReport a problem with this question

9. 9. Blood entering the tube is bright red and pulsating, and the tube fills unusually fast. What is the appropriate response?

   • A.Remove the needle immediately, apply firm direct pressure for at least 5 minutes, and notify the provider✓ Answer
   • B.Decrease the needle angle and keep filling the remaining tubes
   • C.Continue the collection; arterial blood is acceptable for routine chemistry
   • D.Reapply the tourniquet above the site to slow the blood flow

   Those findings indicate accidental arterial puncture. Arterial pressure causes rapid hematoma formation and prolonged bleeding, so the needle is removed at once and firm pressure held until bleeding stops; the specimen is also flagged as possibly arterial because reference ranges differ.

   Source: CLSI PRE02-Ed8 Chapter 4, accidental arterial punctureReport a problem with this question

10. 10. Midway through a draw, the phlebotomist notices swelling forming rapidly under the skin at the puncture site. What should be done?

    • A.Have the patient bend the elbow tightly over gauze to stop the swelling
    • B.Keep the tourniquet in place and press on the swelling while the last tube fills
    • C.Release the tourniquet, remove the needle, and apply direct pressure to the site✓ Answer
    • D.Advance the needle deeper so the bevel re-enters the vein lumen

    Rapid swelling is a hematoma from blood leaking into surrounding tissue, usually because the needle passed through the far wall or the bevel is only partly in the vein. Continuing the draw enlarges the hematoma, and hematoma pressure on a nerve can cause lasting injury; bending the elbow also worsens it.

    Source: CLSI PRE02-Ed8 Chapter 4, hematoma formation and managementReport a problem with this question

11. 11. A patient becomes pale and diaphoretic and says she feels dizzy while blood is being drawn. What should the phlebotomist do?

    • A.Break an ammonia inhalant under her nose to revive her
    • B.Remove the tourniquet and needle at once, lower her head or lay her supine with legs raised, and stay with her✓ Answer
    • C.Give her juice or candy immediately to raise her blood sugar
    • D.Help her walk outside for fresh air while the tubes are labeled

    These are presyncope signs from a vasovagal response; the priority is removing the sharp and restoring cerebral perfusion by lowering the head or elevating the legs. Ammonia inhalants are no longer recommended because they can trigger bronchospasm in asthmatics, nothing is given by mouth until the patient is fully alert, and the patient is never left alone or allowed to walk.

    Source: CLSI PRE02-Ed8 Chapter 4, dizziness/syncope management and syncope-prevention appendixReport a problem with this question

12. 12. Shortly after the tourniquet is applied, pinpoint red spots appear on the patient's forearm below the tourniquet. What do these indicate?

    • A.Petechiae, suggesting a capillary or platelet defect or an overly tight tourniquet, and predicting prolonged bleeding at the site✓ Answer
    • B.An early hematoma that requires immediate cold application
    • C.That the needle has entered an artery
    • D.An allergic reaction to the latex in the tourniquet

    Petechiae are tiny extravasations of blood from capillaries that cannot withstand the pressure, reflecting capillary fragility, a platelet abnormality, or excessive tourniquet tension. They are not an allergic reaction, but they warn the phlebotomist to hold pressure longer after the draw.

    Source: NHA CPT Domain 3, recognize and respond to complications (petechiae); CLSI PRE02-Ed8 tourniquet application guidanceReport a problem with this question

13. 13. Blood flow stops after the first tube fills only partially. Which action should the phlebotomist take FIRST?

    • A.Withdraw the needle completely and immediately attempt the other arm
    • B.Ask the patient to pump the fist vigorously to push more blood into the tube
    • C.Remove the tube and seat a new tube, since loss of vacuum is a common cause and the tube is changed before the needle is moved✓ Answer
    • D.Probe laterally in the antecubital fossa until blood returns

    CLSI's troubleshooting sequence starts with the least invasive cause: a tube that has lost vacuum or is not fully engaged. Changing or reseating the tube is done before any needle manipulation, and blind probing is prohibited because it risks nerve and artery injury.

    Source: CLSI PRE02-Ed8, "blood specimen that cannot be obtained" — change tube before repositioning needle; prohibition on blind probingReport a problem with this question

14. 14. A phlebotomist has made two unsuccessful venipuncture attempts on an inpatient. What should be done next?

    • A.Attempt a foot vein, which is not counted toward the attempt limit
    • B.Perform a capillary puncture instead and report the change afterward
    • C.Make a third attempt using a winged set on the hand
    • D.Stop, ask another qualified collector to attempt the draw, notify the nurse or provider, and document the attempts✓ Answer

    Two attempts is the accepted maximum for one collector, because repeated punctures increase pain, hematoma, and nerve-injury risk. Foot and ankle veins require provider approval and are not an exception, and substituting a different specimen type without an order changes the ordered test.

    Source: CLSI PRE02-Ed8, limit of two attempts per collector and escalation requirementReport a problem with this question

15. 15. A patient has an easily palpable vein in the medial aspect of the antecubital fossa and an adequate vein in the median aspect. Which choice is correct and why?

    • A.Use the medial vein because it is larger and easier to anchor
    • B.Use the vein in the median aspect, because the brachial artery and major nerves lie in the medial aspect✓ Answer
    • C.Use the medial vein but insert at a shallower 10-degree angle to avoid the artery
    • D.Either vein is equally acceptable; all antecubital veins carry the same risk

    CLSI ranks antecubital sites median first, lateral (cephalic) second, and medial (basilic) last, because the brachial artery and the median and medial antebrachial cutaneous nerves lie in the medial aspect. The basilic area is used only when no acceptable vein is found after surveying both arms; prominence does not override anatomic risk.

    Source: CLSI PRE02-Ed8, antecubital site selection priority (median → lateral → medial last)Report a problem with this question

16. 16. An inpatient has an IV infusing in the left forearm. The right arm has acceptable antecubital veins. What should the phlebotomist do?

    • A.Draw from the right arm, the arm without the IV✓ Answer
    • B.Draw directly from the IV catheter after flushing it with saline
    • C.Draw from the left arm above the IV site, where the blood is undiluted
    • D.Stop the IV for 2 minutes and draw from the left arm above the IV

    The uninvolved arm is always the first choice because IV fluid dilutes the specimen and skews electrolytes and glucose. Drawing above an IV is never acceptable; when the IV arm is unavoidable, the draw is made distal to (below) the IV with the infusion stopped and a discard volume taken, and line draws are performed only by authorized staff with an order.

    Source: CLSI PRE02-Ed8, site selection with an intravenous line in place; NHA CPT Domain 2, site determination to minimize patient riskReport a problem with this question

17. 17. A patient reports a right-side mastectomy performed several years ago. The requisition contains no special instructions. What should the phlebotomist do?

    • A.Perform a heel stick instead to avoid both arms
    • B.Use the unaffected left arm; the mastectomy side may be used only with a provider's order✓ Answer
    • C.Draw from a foot vein without contacting the provider
    • D.Draw from the right arm because the surgery was more than five years ago

    Lymph node removal impairs lymphatic drainage on that side indefinitely, so venipuncture there raises the risk of lymphedema and infection and requires provider authorization regardless of how long ago the surgery occurred. Heel sticks are for infants, and foot veins also require provider approval.

    Source: CLSI PRE02-Ed8, contraindicated sites — mastectomy side requires provider authorizationReport a problem with this question

18. 18. When must blood collection tubes be labeled?

    • A.At the nurses' station afterward, using the requisition as the reference
    • B.At the patient's side immediately after collection, before leaving the patient✓ Answer
    • C.On arrival in the laboratory, where printed labels are available
    • D.Before the draw, so tubes cannot be mixed up during the collection

    Labeling in the patient's presence, immediately after collection, is the only point at which the tube, the patient, and the identifiers can all be verified together; this is why pre-labeling and labeling away from the patient are prohibited. The label must carry two identifiers plus the date, time, and collector's initials or ID.

    Source: CLSI PRE01 (patient and specimen identification), labeling at the point of collection; Joint Commission NPSG.01.01.01 two-identifier requirementReport a problem with this question

19. 19. A phlebotomist leaves the tourniquet in place for about three minutes while searching for a vein, then collects the specimen. Which result change is most likely?

    • A.Falsely elevated total protein, albumin, and calcium✓ Answer
    • B.Falsely decreased hemoglobin and hematocrit
    • C.Falsely decreased total protein and calcium
    • D.No change, because the tourniquet is removed before the needle

    A tourniquet left on longer than one minute causes hemoconcentration: water and small molecules filter out of the vessel while large molecules and cells stay behind, so protein-bound and cellular analytes rise. If vein location takes longer than a minute, release the tourniquet, wait at least two minutes, and reapply.

    Source: CLSI PRE02-Ed8, one-minute tourniquet limit and hemoconcentration effectsReport a problem with this question

20. 20. A patient asks whether she should pump her fist to make the vein easier to find. What is the correct response and rationale?

    • A.Yes, vigorous fist pumping is recommended because it makes the vein easier to palpate
    • B.No; vigorous pumping can falsely elevate potassium, so only a single gentle clench is acceptable✓ Answer
    • C.No, because fist pumping falsely lowers the potassium result
    • D.It makes no measurable difference to any laboratory result

    Repeated forearm muscle contraction releases potassium from muscle cells into the local circulation, and combined with tourniquet stasis it produces pseudohyperkalemia that can trigger an unnecessary critical-value workup. A single gentle fist closure is acceptable.

    Source: CLSI PRE02-Ed8, prohibition on fist pumping (pseudohyperkalemia)Report a problem with this question

21. 21. A specimen is ordered for legal blood alcohol testing. Which site preparation is required?

    • A.70% isopropyl alcohol applied with friction and allowed to air dry
    • B.An alcohol-based chlorhexidine scrub, as used for blood cultures
    • C.A non-alcohol antiseptic such as povidone-iodine, benzalkonium chloride, or soap and water✓ Answer
    • D.An alcohol wipe followed by fanning the site dry to save time

    Any alcohol-containing antiseptic can contaminate the sample and be challenged in court as the source of the measured ethanol, so a non-alcohol preparation is required. Blood alcohol specimens also follow chain-of-custody handling with a sealed container and signed documentation.

    Source: CLSI PRE02-Ed8, site antisepsis for blood alcohol/ethanol testing; NHA CPT Domain 4, blood alcohol site prep and chain of custodyReport a problem with this question

22. 22. The last tube has been removed from the holder. Which action must occur immediately BEFORE the needle is withdrawn?

    • A.Ask the patient to bend the arm at the elbow
    • B.Activate the needle's safety device
    • C.Press firmly on the gauze placed over the puncture site
    • D.Release the tourniquet✓ Answer

    Withdrawing the needle with the tourniquet still on leaves the vein under pressure, which forces blood into the tissue and produces a hematoma. Gauze is laid over the site without pressure until the needle is out, the safety feature is activated at withdrawal, and only then is firm pressure applied with the arm kept extended.

    Source: CLSI PRE02-Ed8, needle removal sequence — tourniquet released before needle withdrawalReport a problem with this question

23. 23. A serum specimen arrives with a red-tinged supernatant after centrifugation. Which pattern of falsely changed results should be expected?

    • A.Falsely elevated glucose and BUN
    • B.Falsely elevated potassium, LDH, and AST✓ Answer
    • C.Falsely decreased potassium and LDH
    • D.Falsely prolonged PT and aPTT

    Red-tinged serum indicates hemolysis: ruptured red cells spill their intracellular contents into the serum, and potassium, LDH, AST, magnesium, phosphorus, and iron are far more concentrated inside the cell than outside. Common causes include a too-small needle bore, forceful syringe aspiration, wet alcohol at the site, vigorous shaking, and underfilled additive tubes.

    Source: CLSI PRE02-Ed8 Chapter 4, hemolysis — causes and effect on analytes; NHA CPT knowledge statement on preanalytical errorsReport a problem with this question

Concept-focused practice questions based on CLSI GP41 (venous blood collection), the CLSI order of draw, and the OSHA Bloodborne Pathogens Standard (29 CFR 1910.1030). Not affiliated with the NHA, ASCP, or CLSI, and not medical advice. Facility protocols and current CLSI standards take precedence — always follow your employer's procedures. About the CPT exam →