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CI-CPT practice questions

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Question 1Blood Collection

A phlebotomist has just completed a venipuncture and is preparing to apply pressure to the site. Which action best follows accepted post-collection practice?

  1. Apply pressure with a clean gauze over the site while keeping the arm extended Correct answer.
  2. Massage the site firmly to disperse any bruising
  3. Apply pressure only after the needle has been removed for at least one minute
  4. Bend the arm sharply at the elbow to compress the site

Explanation

Standard practice is to apply clean gauze and steady pressure over the puncture site with the arm extended, which promotes clot formation and reduces hematoma risk. Bending the arm hides the site and prevents observation for bleeding. Massaging the area can disrupt the forming clot and increase bruising.

Question 2Blood Collection

Which additive is present in a light blue-top coagulation tube?

  1. Potassium EDTA
  2. Sodium heparin
  3. Silica clot activator
  4. Sodium citrate Correct answer.

Explanation

Light blue-top tubes contain sodium citrate, which binds calcium and preserves coagulation factors for testing. EDTA is in lavender tubes, heparin in green tubes, and silica clot activator in serum separator or red tubes.

Question 3Blood Collection

During a routine venipuncture, the needle is inserted and no blood flows into the tube. Which initial step is most appropriate?

  1. Slightly withdraw and redirect the needle without fully removing it Correct answer.
  2. Immediately remove the needle and start over in the same site
  3. Push the needle deeper into the tissue to reach the vein
  4. Advance the tube further into the holder to increase vacuum

Explanation

If no blood returns after insertion, the bevel may be against the vein wall or partially through it. Slight withdrawal and redirection, while keeping the needle under the skin, often restores flow. Pushing deeper risks arterial puncture or nerve injury.

Question 4Blood Collection

Which order of draw is correct when collecting multiple tubes during a single venipuncture?

  1. Light blue, blood culture, EDTA, serum separator, heparin
  2. Serum separator, light blue, blood culture, EDTA, heparin
  3. Blood culture, light blue, serum separator, heparin, EDTA Correct answer.
  4. EDTA, heparin, serum separator, light blue, blood culture

Explanation

The standard order places blood culture tubes first to protect sterility, followed by coagulation tubes, then serum tubes, heparin tubes, and finally EDTA tubes. This sequence minimizes additive cross-contamination between tubes.

Question 5Blood Collection

A patient reports fainting during a previous blood draw. Which precaution is most appropriate before and during the collection?

  1. Perform the draw with the patient seated in a chair with armrests or lying down Correct answer.
  2. Ask the patient to hyperventilate before needle insertion
  3. Proceed with the draw quickly without discussing the history
  4. Have the patient stand and shift weight to maintain circulation

Explanation

Patients with a history of syncope should be positioned reclining or seated securely to prevent injury if they faint. Standing increases fall risk and injury. Hyperventilation does not prevent vasovagal syncope and may worsen symptoms.

Question 6Blood Collection

Which site is generally contraindicated for venipuncture?

  1. The median cubital vein of the non-dominant arm
  2. The basilic vein in the antecubital area
  3. An arm with an active intravenous line and a dialysis fistula on the same side Correct answer.
  4. The cephalic vein distal to the antecubital fossa

Explanation

Areas with dialysis fistulas, grafts, or active IV lines should be avoided because of infection and thrombosis risk. The median cubital, cephalic, and basilic veins are standard collection sites when healthy.

Question 7Blood Collection

A blood specimen is collected in a tube containing EDTA. Which laboratory test is this tube primarily intended for?

  1. Glucose measurement
  2. Blood culture
  3. Complete blood count Correct answer.
  4. Prothrombin time

Explanation

EDTA preserves cell morphology and is the standard additive for hematology testing such as a complete blood count. Prothrombin time uses citrate, glucose is typically measured in fluoride or serum tubes, and blood cultures require dedicated culture bottles.

Question 8Blood Collection

The tourniquet has been applied and the vein is located. How long should the tourniquet remain in place before release?

  1. Three to five minutes
  2. Ten minutes
  3. No longer than one minute Correct answer.
  4. Until the last tube is filled

Explanation

The tourniquet should be released within one minute of application to prevent hemoconcentration and changes in analyte concentrations. Prolonged application can cause hemolysis and inaccurate test results.

Question 9Blood Collection

A phlebotomist notices that a specimen tube was filled short of the required volume for a coagulation test. What is the most appropriate action?

  1. Submit the short-draw specimen because the additive will compensate
  2. Add saline to bring the tube to the fill line
  3. Centrifuge the tube twice and submit the plasma
  4. Recollect the specimen in a new light blue tube filled to the correct volume Correct answer.

Explanation

Coagulation tubes require a precise blood-to-additive ratio; a short draw makes the citrate concentration too high and invalidates results. The correct action is to recollect with a properly filled tube. Adding saline or reprocessing cannot restore the correct ratio.

Question 10Blood Collection

Which action best reduces the risk of hemolysis during specimen collection?

  1. Drawing blood through a small-gauge needle with high vacuum
  2. Forcing blood rapidly into the tube using a syringe
  3. Vigorously shaking the tube after collection to mix the additive
  4. Allowing the blood to flow gently down the tube wall and mixing by gentle inversion Correct answer.

Explanation

Hemolysis is reduced by using appropriate needle gauge, avoiding excessive vacuum, and mixing tubes by gentle inversion rather than shaking. Vigorous handling and forced flow damage red blood cells.

Question 11Blood Collection

What is the primary purpose of the antiseptic step before venipuncture?

  1. To numb the skin and reduce pain
  2. To prevent the blood from clotting in the tube
  3. To dilate the vein for easier access
  4. To reduce transient and resident skin flora at the puncture site Correct answer.

Explanation

Antisepsis reduces skin microorganisms at the puncture site, lowering the risk of contamination and infection. It does not anesthetize, dilate veins, or affect coagulation.

Question 12Blood Collection

A patient is taking warfarin and is scheduled for a coagulation test. Which tube and handling are most appropriate?

  1. Lavender tube because it preserves coagulation factors
  2. Red tube because serum is preferred for coagulation
  3. Green tube because heparin stabilizes clotting times
  4. Light blue tube filled to the line and tested within the required time Correct answer.

Explanation

Coagulation testing requires citrate (light blue) tubes filled to the correct volume and processed within validated time limits. EDTA, heparin, and serum tubes are unsuitable because they alter or lack the required anticoagulant ratio.

Question 13Blood Collection

Which practice is recommended when labeling a blood specimen?

  1. Label only the requisition and leave the tube unlabeled
  2. Label tubes later at the desk using the requisition
  3. Label the tube before entering the patient's room
  4. Label the tube at the patient's side immediately after collection and verify identity Correct answer.

Explanation

Specimen labeling must occur at the bedside immediately after collection, with patient identity verified, to prevent mislabeling errors. Pre-labeling or delayed labeling increases the risk of patient identification errors.

Question 14Blood Collection

A patient has a hematoma forming at the puncture site during collection. What is the most appropriate immediate action?

  1. Stop the draw, remove the needle, and apply firm pressure Correct answer.
  2. Loosen the tourniquet and continue collecting
  3. Redirect the needle deeper into the vein
  4. Continue the draw to finish quickly and then apply ice

Explanation

A developing hematoma indicates blood is leaking into surrounding tissue; the draw should be stopped, the needle removed, and firm pressure applied. Continuing or redirecting increases tissue damage and blood loss.

Question 15Blood Collection

Which specimen would be rejected by the laboratory?

  1. A tube transported in a biohazard bag at room temperature
  2. A tube mixed by gentle inversion after collection
  3. A tube collected in the correct order with a complete label
  4. A tube with a missing patient identifier Correct answer.

Explanation

Specimens lacking proper patient identification cannot be reliably linked to a patient and must be rejected. Correctly labeled, properly mixed, and appropriately transported specimens meet acceptance criteria.

Question 16Blood Collection

What is the recommended angle of needle insertion for a routine antecubital venipuncture?

  1. 90 degrees
  2. 15 to 30 degrees Correct answer.
  3. 45 to 60 degrees
  4. 5 degrees

Explanation

A shallow angle of about 15 to 30 degrees allows the bevel to enter the vein without passing through it. Steeper angles increase the risk of puncturing through the vein or injuring underlying structures.

Question 17Blood Collection

Which factor most directly affects the accuracy of a fasting glucose result?

  1. The brand of gauze applied after collection
  2. The position of the patient's arm during labeling
  3. The color of the tourniquet used
  4. Whether the patient has fasted for the required period Correct answer.

Explanation

Fasting status directly influences glucose concentration, so adherence to the required fasting period is essential for accurate interpretation. Tourniquet color, gauze brand, and arm position during labeling do not affect glucose values.

Question 18Blood Collection

A phlebotomist is collecting blood from a patient with a known latex allergy. Which action is most appropriate?

  1. Double-glove with latex gloves
  2. Use standard latex gloves but avoid powder
  3. Use latex-free gloves and tourniquet Correct answer.
  4. Proceed without gloves to avoid latex contact

Explanation

For a latex-allergic patient, latex-free gloves and tourniquet should be used to prevent an allergic reaction. Avoiding gloves is never acceptable because standard precautions require gloves.

Question 19Blood Collection

Which statement about the use of a syringe versus a vacuum tube system is accurate?

  1. A syringe may be preferred for fragile or small veins where vacuum could collapse the vein Correct answer.
  2. A syringe is preferred for all routine draws because it is faster
  3. A syringe eliminates the need for a tourniquet
  4. A syringe prevents hemolysis in every situation

Explanation

Syringe collection is useful when vacuum pressure could collapse small or fragile veins, allowing gentler aspiration. It does not eliminate tourniquet use, is not universally faster, and does not guarantee absence of hemolysis.

Question 20Blood Collection

What is the correct technique for mixing a tube containing an anticoagulant after collection?

  1. Let the tube stand upright without mixing
  2. Invert the tube gently several times according to the additive requirement Correct answer.
  3. Shake the tube vigorously for ten seconds
  4. Roll the tube between the palms for two minutes

Explanation

Tubes with anticoagulants must be inverted gently a specified number of times to ensure adequate mixing without hemolysis. Vigorous shaking, prolonged rolling, or no mixing can cause clotting or cell damage.

Question 21Blood Collection

A patient has a deep, hard-to-palpate vein in the antecubital area. Which approach is most appropriate?

  1. Palpate carefully, use warmth, and consider a smaller needle with a syringe Correct answer.
  2. Probe the area repeatedly with the needle to locate the vein
  3. Apply the tourniquet for five minutes to engorge the vein
  4. Use the most distal visible vein without palpation

Explanation

Warmth, careful palpation, and gentle aspiration with a smaller needle improve success in difficult veins. Blind probing risks injury, and prolonged tourniquet time causes hemoconcentration.

Question 22Blood Collection

Which type of additive tube is typically used for blood bank compatibility testing?

  1. Silica clot tube
  2. Heparin tube
  3. Sodium citrate tube
  4. EDTA tube Correct answer.

Explanation

EDTA tubes are commonly used for blood bank testing such as ABO/Rh typing and crossmatching because EDTA preserves red cell antigens and prevents clotting. Citrate, heparin, and serum tubes are not standard for this purpose.

Question 23Blood Collection

Which action is most important to prevent needlestick injury after venipuncture?

  1. Place the used needle on the tray until the end of the shift
  2. Immediately activate the safety device and dispose of the needle in a sharps container Correct answer.
  3. Break the needle off the syringe before disposal
  4. Recap the needle carefully using one hand

Explanation

Immediate activation of the safety device and disposal in a sharps container is the key step to prevent needlestick injuries. Recapping, leaving needles on trays, and breaking needles all increase injury risk.

Question 24Blood Collection

A specimen for ammonia testing is being collected. Which handling consideration is most critical?

  1. Expose the tube to light before transport
  2. Allow the specimen to clot at room temperature for one hour
  3. Centrifuge the sample at high speed immediately after collection
  4. Place the tube immediately on ice and transport promptly Correct answer.

Explanation

Ammonia levels rise in blood at room temperature because of red cell metabolism, so specimens should be placed on ice and transported promptly. Delayed processing or room-temperature storage falsely elevates results.

Question 25Blood Collection

Which patient identification practice meets standard requirements before venipuncture?

  1. Verify identity using the room number only
  2. Ask a family member to confirm identity without patient involvement
  3. Ask the patient to state full name and date of birth and compare with the requisition Correct answer.
  4. Assume identity is correct if the patient is asleep

Explanation

Positive patient identification requires at least two identifiers, typically full name and date of birth, matched to the requisition. Room number, assumption, or relying solely on a family member does not meet this standard.

Question 26Blood Collection

A phlebotomist must collect blood from an arm that has a functioning arteriovenous fistula used for dialysis. What is the appropriate action?

  1. Draw directly from the fistula needle port
  2. Draw from the opposite arm, avoiding the fistula side entirely Correct answer.
  3. Draw from the fistula arm but only distal to the fistula
  4. Apply the tourniquet above the fistula and draw distally

Explanation

An arm with a dialysis fistula or graft must be avoided because puncture or pressure can damage the vascular access and cause bleeding or thrombosis. Blood should be collected from the opposite arm when one is available. If both arms are compromised, a clinician should be consulted rather than risking the access site.

Question 27Blood Collection

During a venipuncture, the needle bevel is only partially within the vein and blood flow is poor. Which adjustment is most appropriate?

  1. Probe gently side to side to locate the lumen
  2. Pull back on the plunger or tube to increase suction
  3. Advance the needle slightly to seat the bevel fully in the lumen Correct answer.
  4. Withdraw the needle and reinsert at a steeper angle

Explanation

A partially seated bevel can rest against the vessel wall, restricting flow; gently advancing so the full bevel lies within the lumen usually restores flow. Probing or redirecting blindly increases the risk of hematoma and nerve injury. Increasing suction does not correct a malpositioned bevel and may collapse the vein.

Question 28Blood Collection

Which order of draw is correct when collecting a serum tube with clot activator, a sodium citrate tube, and a heparin tube during a single venipuncture?

  1. Citrate, serum, heparin
  2. Heparin, citrate, serum
  3. Serum, heparin, citrate Correct answer.
  4. Citrate, heparin, serum

Explanation

The standard order places sterile/non-additive and clot-activator serum tubes before sodium citrate, and citrate before heparin. Following this sequence prevents additive carryover that could interfere with coagulation testing. Serum first also allows clotting before anticoagulant tubes are filled.

Question 29Blood Collection

A capillary blood specimen is needed from an infant's heel. Which site on the heel is appropriate?

  1. The central area of the heel pad
  2. The medial or lateral edge of the plantar surface Correct answer.
  3. The posterior curvature of the heel
  4. Directly over the calcaneus bone

Explanation

Heel puncture should be performed on the medial or lateral plantar surface of the heel, where tissue is less likely to involve bone. The central heel and posterior curvature risk puncturing the calcaneus or causing osteomyelitis. Avoiding the bone is the key safety principle.

Question 30Blood Collection

A blood culture set is ordered. What is the recommended collection practice for adult patients?

  1. Collect only anaerobic bottles to reduce contamination
  2. Collect one aerobic bottle from a single site
  3. Collect after antibiotics have been started
  4. Collect aerobic and anaerobic bottles from each of two separate sites Correct answer.

Explanation

Standard practice is to collect at least two sets, each including an aerobic and an anaerobic bottle, from separate venipuncture sites. Multiple sites improve detection of intermittent bacteremia and help distinguish contamination. Cultures should be drawn before antimicrobial therapy whenever possible.

Question 31Blood Collection

A patient reports fainting during previous blood draws. Which preparation best reduces the risk of injury during the current collection?

  1. Have the patient stand during the draw for stability
  2. Position the patient reclining or supine before the draw Correct answer.
  3. Ask the patient to hold their breath during the procedure
  4. Perform the draw with the patient seated upright in a chair

Explanation

A reclining or supine position maintains cerebral perfusion if syncope occurs and reduces the chance of a fall. Seated or standing positions increase injury risk if the patient loses consciousness. Breath-holding does not prevent vasovagal syncope.

Question 32Blood Collection

A phlebotomist is about to collect blood from a patient with a known bleeding disorder. Which precaution is most important?

  1. Collect the specimen from a fingerstick instead
  2. Skip the antiseptic step to avoid skin irritation
  3. Apply firm pressure for an extended period after needle removal Correct answer.
  4. Use a smaller needle to reduce trauma

Explanation

Patients with bleeding disorders need prolonged firm pressure after venipuncture to prevent hematoma and continued bleeding. Needle size does not eliminate the bleeding risk. Skin antisepsis must never be skipped, and fingerstick is not a substitute for a needed venous sample.

Question 33Blood Collection

Which statement correctly describes the use of a winged (butterfly) collection set?

  1. It is only used for arterial punctures
  2. It allows flexible tubing for small or fragile veins Correct answer.
  3. It eliminates the need for a tourniquet
  4. It is preferred for large-volume collections in adults

Explanation

A winged set uses short tubing and a small needle, making it useful for fragile, small, or hard-to-reach veins. It does not eliminate the need for a tourniquet and is not the choice for high-volume adult draws. It is used for venous, not arterial, collection.

Question 34Blood Collection

A phlebotomist is collecting blood in a tube containing sodium citrate. Which action is essential to ensure accurate coagulation results?

  1. Shake the tube vigorously after collection
  2. Fill the tube to the indicated volume and mix gently Correct answer.
  3. Collect the tube after a heparin tube
  4. Allow the tube to clot at room temperature

Explanation

Citrate tubes must be filled to the marked volume to maintain the correct blood-to-anticoagulant ratio, and they must be mixed gently to prevent clotting. Vigorous shaking causes hemolysis. Collecting after a heparin tube risks contamination, and citrate tubes must not be allowed to clot.

Question 35Blood Collection

Which practice is correct when preparing the skin for a venipuncture with an alcohol wipe?

  1. Use alcohol only if the skin appears dirty
  2. Apply the antiseptic and allow it to dry before puncture Correct answer.
  3. Wipe once quickly and puncture immediately
  4. Wipe with alcohol and then fan the site with a hand

Explanation

The antiseptic must be allowed to dry on the skin to achieve its full antimicrobial effect and to avoid stinging. Puncturing while wet reduces effectiveness. Fanning with a hand can recontaminate the site, and antisepsis is required regardless of visible cleanliness.

Question 36Blood Collection

A phlebotomist needs to collect a specimen for a therapeutic drug level. Which timing principle is most appropriate?

  1. Collect immediately after the dose for peak levels
  2. Collect at the specified time relative to the dose, such as a trough Correct answer.
  3. Collect at any time regardless of dosing schedule
  4. Collect only when the patient reports symptoms

Explanation

Therapeutic drug monitoring depends on collecting the sample at the specified time relative to dosing, commonly a trough just before the next dose. Random timing yields uninterpretable results. Peak and trough requirements differ by drug and must follow the order.

Question 37Blood Collection

What is the primary reason for using a discard tube before collecting a coagulation specimen with a winged set?

  1. To test whether the vein has been entered
  2. To reduce the patient's blood volume
  3. To remove air from the tubing so the citrate tube fills correctly Correct answer.
  4. To warm the needle before collection

Explanation

When a winged set is used, the dead space in the tubing can contain air that would otherwise enter the citrate tube and reduce its fill volume. Drawing a discard tube clears the air so the coagulation tube fills to the correct ratio. It is not used for warming, vein testing, or volume reduction.

Question 38Blood Collection

Which factor should be documented when a specimen is collected from a patient receiving intravenous fluids?

  1. The color of the IV tubing
  2. The patient's room number
  3. The site of collection relative to the IV line Correct answer.
  4. The brand of the IV catheter

Explanation

Collecting downstream of an IV line can dilute the specimen with infusate, so the collection site relative to the IV must be documented and the other arm used when possible. Catheter brand, tubing color, and room number do not affect specimen integrity. Documentation supports interpretation of potentially diluted results.

Question 39Blood Collection

A phlebotomist must collect blood from a patient with severe burns over both arms. Which approach is most appropriate?

  1. Refuse to collect the specimen
  2. Draw from an area of intact, unburned skin or consult for an alternative site Correct answer.
  3. Draw through the burned tissue to avoid other sites
  4. Draw from the burned area after applying extra antiseptic

Explanation

Burned tissue is compromised and prone to infection and poor healing, so venipuncture should be performed through intact skin at an alternative site. Extra antisepsis does not make burned tissue acceptable. Refusing without exploring alternatives is not appropriate; consultation can identify a safe site.

Question 40Blood Collection

Which action best protects the integrity of a specimen for bilirubin testing after collection?

  1. Freeze the tube immediately
  2. Allow the tube to sit at room temperature for hours
  3. Expose the tube to bright light before transport
  4. Protect the tube from light and transport promptly Correct answer.

Explanation

Bilirubin is light-sensitive and degrades when exposed to light, so the tube should be protected from light and transported promptly. Freezing and prolonged room-temperature storage can also alter results. Prompt, light-protected transport preserves the analyte.

Question 41Specimen Handling and Processing

A peripheral blood smear is being prepared from an EDTA tube that arrived in the laboratory 6 hours after collection. Which change is most likely to be observed on the smear?

  1. Drying artifact with echinocytes
  2. Red cell spherocytes and smudge cells
  3. Platelet satellitism around neutrophils Correct answer.
  4. Neutrophil nuclear hypersegmentation

Explanation

EDTA anticoagulated blood left standing for several hours can show platelet satellitism, in which platelets rosette around neutrophils, and neutrophils may also show degenerative vacuolation. Smears should ideally be made within 2 to 4 hours of collection to avoid these artifacts. Recognizing the timing helps the reviewer avoid misinterpreting the finding as immune-mediated.

Question 42Specimen Handling and Processing

Which anticoagulant is preferred for a blood specimen submitted for osmotic fragility testing?

  1. Potassium EDTA
  2. Lithium heparin Correct answer.
  3. Sodium fluoride
  4. Sodium citrate

Explanation

Heparin is the anticoagulant of choice for osmotic fragility because it does not alter red cell osmotic behavior. EDTA and citrate change the ionic environment and can shift the fragility curve, while fluoride preserves glucose but distorts red cell metabolism. Using heparin keeps the test result comparable to reference values.

Question 43Specimen Handling and Processing

A 24-hour urine specimen for creatinine clearance arrives without preservative and was kept at room temperature. What is the primary concern?

  1. Photodegradation of creatinine
  2. Bacterial overgrowth degrading creatinine Correct answer.
  3. Adsorption of creatinine to the container wall
  4. Volatilization of creatinine

Explanation

Unpreserved urine held at room temperature supports bacterial proliferation, which can consume or alter analytes including creatinine. Collection vessels for clearance studies should be refrigerated or chemically preserved during the collection period. Proper handling protects the accuracy of the calculated clearance.

Question 44Specimen Handling and Processing

A blood culture set is ordered for an adult with suspected sepsis. Which collection practice best supports recovery of the organism?

  1. Inoculate the bottles after the tube for the chemistry panel
  2. Draw both bottles from the same venipuncture site at the same time Correct answer.
  3. Draw one aerobic bottle now and the second set 12 hours later
  4. Collect the anaerobic bottle only when a wound is present

Explanation

For each blood culture set, the aerobic and anaerobic bottles should be filled from a single venipuncture to distribute the blood evenly and reduce contamination risk. Sets are typically collected from separate sites or at intervals to improve yield. Delaying the second bottle of a set reduces the volume recovered at that draw.

Question 45Specimen Handling and Processing

A tissue specimen for routine histology is placed in 10% neutral buffered formalin. What is the primary purpose of the buffer?

  1. To preserve nucleic acids for molecular testing
  2. To accelerate fixation by raising temperature
  3. To decalcify bone within the specimen
  4. To prevent formation of formalin pigment and pH drift Correct answer.

Explanation

Neutral buffered formalin uses phosphate buffer to maintain a near-neutral pH, which prevents acid formalin pigment and preserves antigenicity and morphology. Unbuffered formalin becomes acidic as it oxidizes and can produce pigment deposits. Buffer choice is therefore central to consistent histologic quality.

Question 46Specimen Handling and Processing

A sample for plasma ammonia is collected in an EDTA tube and transported on ice. Which statement explains why this handling is problematic?

  1. Ice causes hemolysis that falsely lowers ammonia
  2. EDTA binds ammonia and removes it from measurement
  3. Ammonia is unstable in EDTA and evaporates rapidly
  4. EDTA interferes with the enzymatic assay, and ice delays separation of plasma Correct answer.

Explanation

EDTA can interfere with some ammonia assays, and chilling the specimen slows red cell metabolism but also delays plasma separation, allowing ammonia to continue to accumulate. Ammonia should be collected in a suitable tube and plasma separated promptly. Following the specific tube and transport requirements protects result validity.

Question 47Specimen Handling and Processing

Which specimen is appropriate for a sweat chloride test used in the evaluation of cystic fibrosis?

  1. Saliva collected after fasting
  2. A single drop of capillary blood
  3. Sweat collected after pilocarpine iontophoresis Correct answer.
  4. A random urine sample

Explanation

Sweat chloride testing requires stimulation of sweating with pilocarpine iontophoresis followed by collection of an adequate sweat sample on gauze or filter paper. The sweat is then analyzed for chloride concentration. Blood, urine, and saliva do not reflect sweat gland chloride transport.

Question 48Specimen Handling and Processing

A laboratory receives a 24-hour sputum collection for acid-fast bacilli culture. Which processing step is most appropriate before culture?

  1. Digestion and decontamination with N-acetyl-L-cysteine and sodium hydroxide Correct answer.
  2. Filtration through a 0.22-micron filter
  3. Direct inoculation without pretreatment
  4. Fixation in formalin

Explanation

Respiratory specimens for mycobacterial culture are typically digested and decontaminated, commonly with N-acetyl-L-cysteine and sodium hydroxide, to liquefy mucus and suppress faster-growing flora. The treated specimen is then concentrated and inoculated. Direct inoculation without decontamination risks overgrowth of commensals.

Question 49Specimen Handling and Processing

A serum separator tube is centrifuged and the serum is left in contact with the gel barrier and cells for 4 hours before testing. Which analyte is most likely to be falsely elevated?

  1. Glucose
  2. Potassium Correct answer.
  3. Sodium
  4. Chloride

Explanation

Prolonged contact between serum and cells allows potassium to leak from red cells into the serum, falsely elevating the result. Glucose tends to fall as cells consume it, while sodium and chloride are relatively stable. Prompt separation or timely analysis prevents this preanalytical error.

Question 50Specimen Handling and Processing

Which practice is correct when labeling a specimen container at the bedside?

  1. Label the container in the patient's presence after confirming identity Correct answer.
  2. Label the container at the nursing station after the draw
  3. Label only the requisition and leave the container unlabeled
  4. Label the container before entering the patient room using the order form

Explanation

Specimen containers should be labeled in the patient's presence after verifying identity with two identifiers, which links the specimen to the correct patient at the point of collection. Pre-labeling or labeling away from the bedside invites misidentification. The requisition alone does not substitute for container labeling.