NHA CPT NHA Certified Phlebotomy Technician - Set 5 - Part 1

Correct Answer: Form a barrier between cells and serum

the thixotropic gel migrates between cells and serum during centrifugation, hardening into a stable barrier within minutes. The barrier prevents cells from re-mixing with serum during transport and downstream handling. Option a is incorrect because clot formation is accomplished by silica or other clot activators, not by the thixotropic gel. The gel is purely a physical separator that flows during the spin and hardens afterward. Option b is incorrect because platelet sedimentation is a separate centrifugation effect rather than the role of gel. The gel exists to keep cellular elements physically separated from serum, not to sediment platelets specifically. Option d is incorrect because concentration of microorganisms is not the role of separator gel in routine chemistry tubes. Cultures use entirely different broth-based bottles, not gel separator tubes for microbial growth detection.

Correct Answer: Swinging-bucket rotor

the swinging-bucket rotor swings tubes horizontally during the spin, producing a flat horizontal interface ideal for SST gel formation. Routine clinical chemistry laboratories use this rotor design for serum and plasma separation. Option b is incorrect because the fixed-angle rotor holds tubes at a tilted angle and produces an angled cell interface. The tilted interface is less ideal for clean serum-cell separation and is used in different applications. Option c is incorrect because the cytocentrifuge is a specialized device that deposits cells onto a slide for cytology examination. It does not produce serum or plasma for chemistry analysis from a routine SST tube. Option d is incorrect because the microcentrifuge spins very small volumes at very high speed for hematocrit or molecular work. It is not the routine choice for SST chemistry separation, since it accommodates only small tubes.

Correct Answer: Refrigerated centrifuge

the refrigerated centrifuge maintains the chamber at four degrees Celsius during the spin. The cold chamber preserves thermolabile analytes such as ammonia, lactate, ACTH, gastrin, and parathyroid hormone during processing. Option a is incorrect because the microcentrifuge is a small bench-top device for tiny volumes at very high speed. It is not specifically refrigerated and would not protect thermolabile analytes during the spin without a refrigerated chamber. Option b is incorrect because a standard fixed-angle bench centrifuge does not refrigerate the chamber. Without chilling, thermolabile analytes degrade during the spin, so the standard refrigerated centrifuge is needed instead. The standard reflects current practice in routine clinical phlebotomy. Option c is incorrect because the cytocentrifuge is for cytology slide preparation rather than thermolabile chemistry analytes. It does not maintain a refrigerated chamber for analyte preservation during spinning at all. The standard

Correct Answer: Thirty minutes

gel SST tubes require thirty minutes of clotting time before centrifugation. Spinning earlier produces latent fibrin clots that clog analyzer probes and disrupt the gel barrier during the analytical run. Option a is incorrect because zero minutes applies to plasma tubes containing anticoagulant, where clotting is prevented entirely. SST tubes have a clot activator, so they need time to clot before any centrifugation occurs. Option c is incorrect because five minutes applies to the rapid serum tube containing thrombin rather than the standard SST. The SST relies on silica plus gel and needs the full thirty minutes to complete clotting. Option d is incorrect because two hours far exceeds the necessary clotting interval and delays processing. Thirty minutes is the standard SST minimum, with longer waits offering no benefit to specimen quality during routine chemistry.

Correct Answer: Draw a new tube

the standard requires drawing a new tube when more serum is needed. Re-centrifuging an SST risks cracking the gel barrier, releasing intracellular potassium and lactate dehydrogenase into the serum. Option b is incorrect because re-centrifuging the SST is contraindicated because the hardened gel can crack during the second spin. Cracked gel allows cells to re-contact serum, producing dramatic potassium and lactate dehydrogenase errors. Option c is incorrect because flipping the tube and re-spinning still re-centrifuges the same tube and risks the same gel barrier cracking. The standard always requires a new tube for additional serum requirements. Option d is incorrect because heating the gel does not safely soften the barrier and would not produce additional serum reliably. The thixotropic gel is engineered to harden once, and reheating creates instability rather than additional usable specimen.

Correct Answer: One to thirteen hundred g, ten minutes

the typical clinical range for routine SST processing is one thousand to thirteen hundred g for ten minutes. The range balances complete cell sedimentation with avoiding hemolysis or gel barrier disruption. Option a is incorrect because three hundred g for two minutes is far below the standard SST processing range. The lower force fails to drive complete sedimentation, leaving cells suspended in serum and producing inadequate separation. Option b is incorrect because five thousand g for two minutes exceeds the standard range and risks hemolysis from excessive force. Routine SST processing uses moderate force over a longer interval to achieve clean separation safely. Option d is incorrect because ten thousand g for one minute is far above the range and would risk hemolysis. The standard uses moderate force for ten minutes rather than extreme force for short intervals.

Correct Answer: Distribute at one hundred twenty degree intervals

three tubes naturally balance when distributed at one hundred twenty degree intervals around the rotor. Placing them in positions one, three, and five of a six-position rotor creates symmetric balance about the center. Option a is incorrect because placing all three together in one half creates severe imbalance during the spin. The rotor would vibrate violently and could fracture, breaking glass tubes and aerosolizing infectious blood contents. Option b is incorrect because placing tubes in adjacent positions creates side-heavy imbalance about the rotor center. The rotor must be balanced symmetrically, which adjacent placement does not achieve in a six-position rotor. Option c is incorrect because two opposite plus one with counter-tube works but is not the simplest approach for three patient tubes. The natural one hundred twenty degree distribution avoids the need for any counter-tube during spinning.

Correct Answer: Balance with water-filled counter-tube

the standard balances a single patient tube with a water-filled counter-tube of identical type and weight, placed in the opposing position. The counter-tube creates the symmetry needed for safe centrifugation. Option b is incorrect because spinning a single tube alone in any position creates severe imbalance during the spin. The rotor would vibrate and could fracture, posing a serious safety hazard during the procedure. Option c is incorrect because spinning uncapped is prohibited under OSHA rules because it aerosolizes infectious blood. Single tubes must be capped throughout centrifugation, with a counter-tube ensuring rotor balance during the run. Option d is incorrect because centering a single tube is not an option in standard centrifuges, which have peripheral positions only. The rotor lacks a center receptacle, so the answer must use a counter-tube for balance.

Correct Answer: OSHA Bloodborne Pathogens Standard

OSHA's Bloodborne Pathogens Standard prohibits practices that aerosolize infectious blood, including centrifuging unstoppered tubes. The cap must remain in place throughout centrifugation to prevent aerosol exposure during the spin. Option a is incorrect because HIPAA covers patient health information privacy and is unrelated to centrifuge stoppering practices. The rule involved here is the bloodborne pathogen exposure rule rather than information privacy. The standard reflects current practice in routine clinical phlebotomy. Option c is incorrect because CLIA quality control rules address analytical accuracy and proficiency testing rather than aerosol exposure. The cap rule comes from the bloodborne pathogen standard, which addresses worker safety. The standard reflects current practice in routine clinical phlebotomy. Option d is incorrect because ANSI Z358.1 covers emergency eyewash and shower equipment requirements rather than centrifuge stoppering. The relevant regulation is O

Correct Answer: Plus or minus five percent

the CLSI standard requires centrifuge rpm verification to be within plus or minus five percent of the displayed value. Monthly verification with an external tachometer documents this tolerance for the maintenance log. Option a is incorrect because plus or minus one percent is tighter than the CLSI standard requires. The actual tolerance sits at five percent, which is achievable across most commercial laboratory centrifuges in routine maintenance. Option b is incorrect because plus or minus twenty percent is far too loose and would allow significant analytical variation. The CLSI standard tightens this tolerance to five percent for reliable separation across runs over time. Option d is incorrect because plus or minus fifty percent is so loose that the centrifuge would essentially be uncalibrated. The standard sets five percent as the tolerance to ensure consistent force across runs.

Correct Answer: Amber tube or foil-wrapped tube

amber tubes or foil-wrapped tubes protect photosensitive analytes like bilirubin from photodegradation. The light barrier prevents oxidation of bilirubin during processing and transport, preserving the analyte for accurate measurement. Option a is incorrect because clear plastic test tubes allow ambient light to reach the specimen, accelerating bilirubin photodegradation. The standard avoids clear containers entirely for any photosensitive analyte during routine handling and transport. Option b is incorrect because heat-sealed clear pouches still allow light to reach the specimen and offer no photoprotection. The standard requires opaque amber containers or foil wrap, regardless of pouch sealing during transport. Option c is incorrect because refrigeration alone does not protect against light degradation of bilirubin. Cold slows oxidation but does not block the photons that drive bilirubin breakdown in clear containers. The standard reflects current practice in routine clinical phlebot

Correct Answer: Cryoglobulins and cold agglutinins

cryoglobulins and cold agglutinins require warm transport at thirty-seven degrees Celsius. Cooling causes precipitation that produces false-negative results, so warm transport from bedside through processing is essential. Option b is incorrect because ammonia and lactate are classic ice slurry analytes rather than warm transport analytes. They require cold transport to slow ongoing in vitro metabolism, the opposite of cryoglobulin handling. Option c is incorrect because ACTH and gastrin require cold transport rather than warm. Both are thermolabile peptides degraded by warmth, so they belong to the ice slurry category in routine processing. The standard reflects current practice in routine clinical phlebotomy. Option d is incorrect because bilirubin and folate require light protection rather than warm transport. Both are photosensitive analytes managed with amber tubes or foil wrap, not with thirty-seven degree warming during transport.

Correct Answer: Two identifiers

the Joint Commission requires at least two patient-specific identifiers on every specimen container, including aliquot tubes. The two identifiers must travel with the patient and not depend on temporary location. Option a is incorrect because four identifiers exceed the Joint Commission minimum and are not required for routine aliquot labels. The rule sets two identifiers, with additional information optional based on facility procedure rather than mandate. Option b is incorrect because one identifier creates an unacceptably high error rate and does not satisfy the patient safety goal. Wrong-blood-in-tube events cluster around single-identifier shortcuts, the failure mode this rule prevents. Option d is incorrect because three identifiers exceed the Joint Commission floor and many transfusion services do require three. However, the routine standard for aliquot labels is two, with three reserved for the highest-stakes encounters.

Correct Answer: Routine SST aliquot, approximate volume

pour-off works well for routine aliquot transfer from an SST where volume is approximate and the gel barrier prevents cell carryover. The technique is fast and reduces aerosol generation compared with pipetting. Option a is incorrect because sending out a reference test requiring exact volume favors pipetting rather than pour-off. Calibrated transfer pipettes provide precise volume control, which the gravity pour cannot match reliably. Option c is incorrect because multiple aliquots of differing volumes favor pipetting because each volume can be precisely measured. Pour-off cannot deliver several different specific volumes from a single primary tube. The standard reflects current practice in routine clinical phlebotomy. Option d is incorrect because tubes with no gel and loose cells favor pipetting to avoid drawing cells with serum. Pour-off would risk transferring cells during the gravity tilt, distorting downstream chemistry results.

Correct Answer: Hemogard closure or gauze barrier with shield

the safer technique uses a Hemogard-style closure or a gauze barrier between the operator and the tube, with face shield or splash guard. The combination prevents aerosols and droplet exposure during the tube opening. Option a is incorrect because popping the cap with thumbs alone exposes the operator to aerosols when the closure releases. The standard requires a barrier and splash protection, not bare-thumb manipulation of stoppered tubes. Option b is incorrect because opening quickly with one hand still aerosolizes when the cap releases, regardless of speed. The standard uses a barrier such as gauze or Hemogard, plus splash protection, rather than relying on speed. Option c is incorrect because twisting the cap toward the face is dangerous and exposes the operator to direct splash. The standard always orients the cap away from the face, with appropriate barrier protection during the opening.

Correct Answer: About seven percent per hour

whole blood glucose drops approximately seven percent per hour at room temperature without an inhibitor. Erythrocytes and leukocytes continue glycolysis in vitro, consuming glucose until the specimen is processed. Option b is incorrect because half a percent per hour dramatically understates the actual glycolysis rate. Published data place the rate near seven percent per hour, which is why fluoride preservation matters for delayed-transport glucose specimens. Option c is incorrect because twenty-five percent per hour overstates the actual rate by a wide margin. The published rate is closer to seven percent per hour, which still meaningfully changes results during transport delays. Option d is incorrect because fifty percent per hour is far above the actual rate. The published value sits near seven percent per hour, which is enough to invalidate fasting glucose if the specimen sits for several hours.

Correct Answer: Room temperature, prothrombin within twenty-four hours

unspun citrated whole blood holds at room temperature, with prothrombin time accepted within twenty-four hours and partial thromboplastin time within four hours. CLSI specifies these intervals to maintain assay accuracy. Option a is incorrect because frozen storage of unspun whole blood ruptures cells and invalidates coagulation testing. Whole blood freezing is not used for coagulation specimens at any stage of routine processing. The standard reflects current practice in routine clinical phlebotomy. Option b is incorrect because refrigeration of unspun citrated specimens activates platelets and shortens partial thromboplastin time falsely. The standard holds these specimens at room temperature rather than refrigerated during the wait. The standard reflects current practice in routine clinical phlebotomy. Option d is incorrect because body temperature transport applies to cryoglobulins and cold agglutinins, not coagulation specimens. The room temperature standard applies to unspun citr

Correct Answer: Sodium fluoride and potassium oxalate

the gray-top tube contains sodium fluoride to inhibit glycolysis through enolase blockade, and potassium oxalate as the anticoagulant. The combination preserves glucose and lactate during transport and storage. Option a is incorrect because potassium EDTA is the lavender-tube additive for hematology, not the gray-tube combination. EDTA does not inhibit glycolysis adequately for glucose preservation in delayed-transport specimens. The standard reflects current practice in routine clinical phlebotomy. Option c is incorrect because sodium citrate at three point two percent is the light-blue tube anticoagulant for coagulation testing. Citrate prevents clotting through calcium chelation but does not block glycolysis, so it does not match. Option d is incorrect because sodium heparin is the green-tube anticoagulant for plasma chemistry. Heparin prevents clotting but does not inhibit glycolysis, so glucose continues dropping during transport in heparin tubes. The standard reflects current pra

Correct Answer: Potassium

potassium concentrates roughly twenty-five times higher inside red cells than in plasma. Hemolysis releases that intracellular potassium into serum, falsely elevating reported potassium results dramatically and risking misdiagnosis of hyperkalemia. Option a is incorrect because sodium is similar in concentration inside and outside cells, so hemolysis affects sodium minimally. The ion most affected by hemolysis is potassium because of the steep intracellular-extracellular gradient. Option b is incorrect because chloride is similar in concentration across the cell membrane, so hemolysis affects chloride minimally. Potassium is the dominant intracellular ion affected by red cell rupture during hemolysis. The standard reflects current practice in routine clinical phlebotomy. Option c is incorrect because calcium is mostly extracellular, so hemolysis affects calcium less than potassium. The classic hemolysis interference is on potassium, lactate dehydrogenase, aspartate aminotransferase, an

Correct Answer: Seven days

separated serum potassium holds for approximately seven days at refrigerated temperature between two and eight degrees Celsius. The cold environment preserves the analyte once cells are separated from the serum. Option a is incorrect because four hours dramatically understates the stability of separated serum potassium at refrigerated temperature. The published value is closer to seven days, which supports routine batch processing in chemistry laboratories. Option b is incorrect because twelve hours still understates the refrigerated stability of separated serum potassium. Routine chemistry stability tables list approximately seven days, allowing reasonable storage windows before analysis. The standard reflects current practice in routine clinical phlebotomy. Option d is incorrect because one year overstates the refrigerated stability and would only apply to frozen storage at minus twenty Celsius. Refrigerated separated serum potassium holds for around seven days rather than indefinite