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ASCP PBT practice questions

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Question 1Phlebotomy

Which needle gauge is most appropriate for routine venipuncture of a healthy adult with a prominent median cubital vein?

  1. 16 gauge
  2. 30 gauge
  3. 21 gauge Correct answer.
  4. 25 gauge

Explanation

A 21-gauge needle is the standard choice for routine adult venipuncture because it balances adequate blood flow with vessel and patient comfort. Larger gauges (smaller numbers) increase trauma risk, and much smaller gauges are reserved for fragile or pediatric veins.

Question 2Phlebotomy

What is the maximum recommended length of time a tourniquet should remain applied during a routine venipuncture?

  1. 10 minutes
  2. 10 seconds
  3. 5 minutes
  4. 1 minute Correct answer.

Explanation

A tourniquet should be released within 1 minute of application. Prolonged constriction causes hemoconcentration and shifts in analyte concentrations, and it increases patient discomfort.

Question 3Phlebotomy

In the standard order of draw for evacuated tubes, which tube is collected first?

  1. Lavender EDTA
  2. Light blue sodium citrate
  3. Blood culture Correct answer.
  4. Serum separator

Explanation

Blood culture tubes are drawn first to minimize contamination risk from skin flora and to preserve sterility. Sterile or additive-free considerations place them ahead of coagulation and additive tubes.

Question 4Phlebotomy

Which additive is present in a lavender-top evacuated tube?

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

Explanation

Lavender-top tubes contain EDTA, typically as the potassium salt, which chelates calcium to prevent clotting. This additive is used for hematology testing such as complete blood counts.

Question 5Phlebotomy

Which site is generally the preferred first choice for venipuncture in an adult?

  1. Dorsal hand veins
  2. Cephalic vein
  3. Median cubital vein Correct answer.
  4. Basilic vein

Explanation

The median cubital vein is preferred because it is well anchored, large, and less likely to roll or injure nearby structures. The basilic and cephalic veins are acceptable alternatives but carry more risk or difficulty.

Question 6Phlebotomy

After a venipuncture, which action should the phlebotomist take to promote hemostasis at the site?

  1. Apply pressure with a clean gauze for several minutes Correct answer.
  2. Bend the arm sharply at the elbow
  3. Apply a warm compress immediately
  4. Massage the puncture site briskly

Explanation

Firm pressure with clean gauze for several minutes allows a clot to form and prevents hematoma. Bending the arm or massaging the site can disrupt clot formation and increase bruising.

Question 7Phlebotomy

Which action best describes proper hand hygiene before a venipuncture procedure?

  1. Rinse hands with water only
  2. Apply gloves without washing hands
  3. Wipe hands on a clean paper towel
  4. Use an alcohol-based rub or soap and water, then allow to dry Correct answer.

Explanation

Hands should be cleaned with soap and water or an alcohol-based rub and allowed to dry before donning gloves. This reduces the risk of transmitting organisms to the patient and the site.

Question 8Phlebotomy

What is the primary purpose of cleansing the venipuncture site with an antiseptic before needle insertion?

  1. To numb the skin
  2. To reduce skin flora and prevent contamination Correct answer.
  3. To slow blood flow
  4. To make the vein more visible

Explanation

Antiseptic cleansing reduces transient and resident skin flora at the puncture site, lowering the risk of contaminating the specimen or causing infection. The antiseptic must be allowed to dry before puncture.

Question 9Phlebotomy

A phlebotomist collects a light blue citrate tube and notices the tube is only half filled. What is the most appropriate action?

  1. Add saline to bring the tube to the fill line
  2. Submit the specimen because the color indicates the additive
  3. Recollect the tube to obtain the correct blood-to-additive ratio Correct answer.
  4. Centrifuge the tube twice before testing

Explanation

Citrate tubes require a specific blood-to-additive ratio, and underfilling dilutes the anticoagulant effect, altering coagulation results. The correct action is to recollect a properly filled tube.

Question 10Phlebotomy

During a draw, the phlebotomist notes the blood flow stops and a small bruise begins forming under the skin around the needle. What is the most appropriate immediate response?

  1. Aspirate vigorously with the syringe
  2. Rotate the needle a quarter turn and continue
  3. Withdraw the needle, apply pressure, and select another site Correct answer.
  4. Push the needle deeper to re-enter the vein

Explanation

A developing hematoma indicates the needle has left the vein or the vein is leaking, so the draw should be stopped. The needle is removed, pressure is applied, and a different site is chosen if a specimen is still needed.

Question 11Phlebotomy

A patient reports fainting during a previous blood draw and feels lightheaded as the needle is prepared. What is the best preventive action?

  1. Proceed quickly without pausing
  2. Position the patient reclined and monitor closely Correct answer.
  3. Have the patient stand during the draw
  4. Ask the patient to hold their breath

Explanation

A reclined position reduces the risk of injury from syncope and improves cerebral perfusion if the patient feels faint. Close monitoring and prompt response are essential for patients with a history of vasovagal reactions.

Question 12Phlebotomy

Which specimen tube should be collected before a serum separator tube when both are ordered?

  1. Gray fluoride tube
  2. Green heparin tube
  3. Lavender EDTA tube
  4. Light blue citrate tube Correct answer.

Explanation

Coagulation tubes (light blue) are drawn before serum tubes because additive carryover can affect coagulation testing. The standard order places citrate tubes ahead of serum separator tubes.

Question 13Phlebotomy

A phlebotomist is drawing blood from an arm with an active intravenous line. Which approach is correct?

  1. Draw from the opposite arm whenever possible Correct answer.
  2. Draw from the IV tubing port
  3. Draw from the same arm above the IV site
  4. Draw from the same arm below the IV site

Explanation

Drawing from the arm opposite an IV line avoids specimen dilution and contamination from infusing fluids. If the opposite arm is unavailable, a distal site below the IV may be considered per policy, but the opposite arm is preferred.

Question 14Phlebotomy

Which practice best prevents needlestick injuries during disposal of a used needle?

  1. Bending the needle before disposal
  2. Placing the needle in a biohazard bag
  3. Activating the safety device and placing it in a sharps container immediately Correct answer.
  4. Recapping the needle with one hand

Explanation

Immediately activating the safety feature and depositing the needle in a puncture-resistant sharps container prevents needlestick injuries. Recapping and bending needles are high-risk practices that are discouraged.

Question 15Phlebotomy

A blood specimen for a chemistry panel is collected in a tube containing EDTA. What is the most likely effect on the results?

  1. Falsely elevated glucose only
  2. No effect on any analyte
  3. Improved accuracy of all tests
  4. Falsely low calcium and altered electrolyte results Correct answer.

Explanation

EDTA chelates calcium and also introduces potassium and sodium depending on the salt form, so chemistry results such as calcium and electrolytes are altered. Chemistry testing requires serum or heparinized plasma, not EDTA plasma.

Question 16Phlebotomy

A phlebotomist must collect blood from a patient with a fragile, small vein in the hand. Which equipment combination is most appropriate?

  1. 21-gauge needle with a large-volume tube holder
  2. 18-gauge needle with an evacuated tube
  3. 16-gauge needle with a syringe
  4. 23-gauge butterfly needle with a small-volume tube Correct answer.

Explanation

A small-gauge butterfly needle is suited to fragile or small veins and reduces trauma, and small-volume tubes prevent excessive suction that can collapse the vein. Larger needles are inappropriate for such veins.

Question 17Phlebotomy

Which action is correct when a patient's arm veins are not visible and the first attempt is unsuccessful?

  1. Release the tourniquet, reassess, and try a different site or apply a warm compress Correct answer.
  2. Use a larger needle to improve flow
  3. Apply the tourniquet more tightly and reinsert at the same site
  4. Probe repeatedly with the needle in the same site

Explanation

After an unsuccessful attempt, the tourniquet should be released and the site reassessed; warming the arm can help dilate veins. Repeated probing at one site increases trauma and patient discomfort.

Question 18Phlebotomy

A specimen is collected in a tube with a clot activator but is not mixed. What is the most likely consequence?

  1. The tube will hemolyze immediately
  2. The blood will remain anticoagulated
  3. The additive will be neutralized
  4. The specimen will clot incompletely and yield poor serum Correct answer.

Explanation

Clot activator tubes require gentle inversion to mix the additive with blood so a complete clot forms and serum can be separated. Without mixing, clotting may be incomplete and the serum sample compromised.

Question 19Phlebotomy

Which of the following best describes the correct technique for mixing an anticoagulated blood tube after collection?

  1. Shake vigorously up and down
  2. Vortex on a mixer for one minute
  3. Invert gently several times Correct answer.
  4. Roll between the palms once

Explanation

Gentle inversion several times ensures the additive mixes with the blood without causing hemolysis. Vigorous shaking or vortexing damages red cells and alters results.

Question 20Phlebotomy

A phlebotomist needs to collect a specimen for coagulation testing and also a serum chemistry panel. Which sequence is correct?

  1. Citrate tube, then serum tube Correct answer.
  2. Serum tube, then citrate tube
  3. EDTA tube, then citrate tube
  4. Heparin tube, then citrate tube

Explanation

Coagulation tubes must be drawn before tubes containing other additives to avoid carryover that can interfere with clotting tests. Therefore the citrate tube precedes the serum tube.

Question 21Phlebotomy

A patient has a hematoma forming at the puncture site and reports sharp pain radiating down the arm. What does this most likely indicate?

  1. Arterial puncture or nerve involvement requiring immediate needle withdrawal Correct answer.
  2. Normal venous filling
  3. Proper needle position
  4. Adequate tourniquet pressure

Explanation

Radiating pain and rapid hematoma formation suggest the needle may have struck an artery or nerve, and the needle should be withdrawn immediately. Pressure should be applied longer for arterial punctures, and the event documented.

Question 22Phlebotomy

A phlebotomist collects a specimen in a tube containing sodium citrate but the patient's hematocrit is markedly elevated. Why does this matter?

  1. The additive will evaporate
  2. The citrate volume may be excessive relative to plasma, altering coagulation results Correct answer.
  3. The tube will clot prematurely
  4. The specimen will hemolyze

Explanation

Citrate tubes are formulated for a normal hematocrit; with marked polycythemia, the plasma volume is reduced so the fixed citrate volume is relatively excessive, prolonging clotting times. This can lead to inaccurate coagulation results.

Question 23Phlebotomy

A phlebotomist is asked to draw blood from a patient with a known bleeding disorder and very fragile veins. Which precaution is most important?

  1. Use a larger needle to shorten the procedure
  2. Apply the tourniquet for several minutes to engorge the vein
  3. Use the smallest needle possible and apply extended pressure after the draw Correct answer.
  4. Draw from the most distal small vein available

Explanation

Patients with bleeding disorders require minimal trauma and extended post-puncture pressure to reduce bleeding and hematoma risk. A small needle and careful technique help limit vessel injury.

Question 24Phlebotomy

During a draw, the phlebotomist observes that blood in the tube appears bright red and pulses into the tube under pressure. What is the most appropriate interpretation and action?

  1. This suggests the tourniquet is too loose; tighten it
  2. This suggests arterial puncture; withdraw the needle and apply prolonged pressure Correct answer.
  3. This indicates the tube is underfilled; continue
  4. This is normal venous flow; continue the draw

Explanation

Bright red, pulsatile flow indicates arterial blood, which can occur if the needle enters an artery. The needle should be withdrawn and firm pressure applied for a longer period to prevent hematoma, and the event documented.

Question 25Phlebotomy

A phlebotomist must collect blood from a patient receiving a heparin infusion through a line in the right arm. Which action best ensures an accurate specimen?

  1. Draw from the left arm, away from the infusion Correct answer.
  2. Draw from the right arm above the infusion site
  3. Draw from the infusion line after flushing
  4. Draw from the right arm below the infusion site

Explanation

Drawing from the arm opposite the infusion avoids dilution and contamination by the infusing drug. If only the infused arm is available, special procedures per policy are needed, but the opposite arm is preferred.

Question 26Blood Banking

Which ABO blood type is considered the universal donor for packed red blood cell transfusions?

  1. Type AB positive
  2. Type A positive
  3. Type O negative Correct answer.
  4. Type B negative

Explanation

Type O red cells lack A and B antigens, and O negative red cells also lack the D antigen, so they can be given to recipients of any ABO and Rh type without causing hemolysis. This makes O negative the universal red cell donor.

Question 27Blood Banking

A donor unit is labeled group A, Rh positive. Which antigen is present on the donor red cells in addition to the A antigen?

  1. D antigen Correct answer.
  2. Lewis antigen only
  3. I antigen only
  4. B antigen

Explanation

Rh positive means the D antigen is present on the red cells. Group A indicates the A antigen is present and B antigen is absent.

Question 28Blood Banking

What is the primary purpose of performing a forward and reverse ABO grouping?

  1. To determine the patient's Rh genotype
  2. To screen for irregular red cell antibodies
  3. To detect discrepancies between cell and serum typing Correct answer.
  4. To measure hemoglobin concentration

Explanation

Forward grouping tests the patient's red cells with known antisera, and reverse grouping tests the patient's serum against known A and B cells; comparing them detects discrepancies. Antibody screening and hemoglobin measurement are separate tests.

Question 29Blood Banking

Which anticoagulant is used in the collection of blood products for transfusion because it chelates calcium?

  1. EDTA
  2. CPD Correct answer.
  3. Heparin
  4. Sodium fluoride

Explanation

CPD (citrate-phosphate-dextrose) contains citrate, which binds calcium and prevents coagulation in collected blood units. Citrate-based solutions are standard for blood bank collection.

Question 30Blood Banking

What is the storage temperature range for whole blood and packed red blood cells?

  1. 20 to 24 degrees C
  2. 1 to 6 degrees C Correct answer.
  3. -18 to -25 degrees C
  4. 37 degrees C

Explanation

Red cells and whole blood are stored refrigerated at 1 to 6 degrees C to slow metabolic activity while maintaining viability. Room temperature, frozen, and body temperature are not appropriate for red cell storage.

Question 31Blood Banking

Which immunoglobulin class is responsible for naturally occurring ABO antibodies in serum?

  1. IgM Correct answer.
  2. IgA
  3. IgG
  4. IgE

Explanation

Naturally occurring ABO antibodies are predominantly IgM, which are large pentameric molecules that agglutinate red cells directly in saline. IgG ABO antibodies may also be present but are not the predominant naturally occurring class.

Question 32Blood Banking

What does a positive antibody screen indicate?

  1. An unexpected red cell antibody may be present Correct answer.
  2. The patient is ABO incompatible with all donors
  3. The patient's red cells are polyagglutinable
  4. The patient has a coagulopathy

Explanation

A positive antibody screen suggests the presence of an unexpected (non-ABO) red cell antibody that requires identification. It does not by itself indicate ABO incompatibility, coagulation problems, or polyagglutination.

Question 33Blood Banking

Which test is used to confirm the ABO type of a donor unit before labeling?

  1. Hemoglobin electrophoresis
  2. Repeat forward and reverse grouping on the donor sample Correct answer.
  3. Crossmatch against recipient serum
  4. Direct antiglobulin test

Explanation

Donor units are confirmed by repeating forward and reverse grouping on the donor sample to ensure the label matches the unit. The direct antiglobulin test, crossmatch, and hemoglobin electrophoresis serve different purposes.

Question 34Blood Banking

A patient's serum reacts with A1 cells but not with B cells, and the red cells react with anti-A but not anti-B. Which ABO discrepancy pattern is most consistent with these findings?

  1. Group B with extra anti-A
  2. Group AB with missing B antibody
  3. A subgroup with weak A antigen expression Correct answer.
  4. Group O with missing anti-A

Explanation

Weak or missing reverse anti-A with positive forward anti-A suggests an A subgroup such as A2 or weaker, where the patient may produce anti-A1. The forward and reverse results do not match a simple group AB, O, or B pattern.

Question 35Blood Banking

A patient's serum contains anti-D. Which red cell unit would be most appropriate for transfusion?

  1. Weak D positive
  2. D negative Correct answer.
  3. D positive
  4. D positive with a negative crossmatch

Explanation

A patient with anti-D must receive D negative red cells to avoid a hemolytic transfusion reaction. D positive and weak D positive units carry the D antigen and would be incompatible.

Question 36Blood Banking

Which antibody is most commonly associated with delayed hemolytic transfusion reactions?

  1. Anti-B
  2. Anti-Jka Correct answer.
  3. Anti-I
  4. Anti-A

Explanation

Delayed hemolytic transfusion reactions are most often caused by anamnestic IgG antibodies to red cell antigens such as Kidd (Jka), Rh, or Kell. Anti-A and anti-B cause acute hemolytic reactions, and anti-I is typically a cold autoantibody.

Question 37Blood Banking

What is the purpose of the immediate spin crossmatch?

  1. To detect IgG antibodies only
  2. To detect ABO incompatibility between donor and recipient Correct answer.
  3. To measure complement activity
  4. To confirm the donor's Rh type

Explanation

The immediate spin crossmatch primarily detects ABO incompatibility by demonstrating IgM-mediated agglutination. It does not detect IgG antibodies, measure complement, or confirm Rh typing.

Question 38Blood Banking

Which of the following is a characteristic of the indirect antiglobulin test (IAT)?

  1. It is used only for ABO typing
  2. It detects antibodies that sensitize red cells in vitro Correct answer.
  3. It requires no washing steps
  4. It detects antibodies bound to red cells in vivo

Explanation

The IAT detects antibodies in serum that bind to red cells during incubation in vitro, requiring washing and addition of antihuman globulin. The direct antiglobulin test detects in vivo sensitization.

Question 39Blood Banking

A unit of platelets is stored at 20 to 24 degrees C with continuous agitation primarily to do which of the following?

  1. Prevent bacterial growth
  2. Activate platelets for transfusion
  3. Maintain platelet viability and gas exchange Correct answer.
  4. Increase platelet count

Explanation

Platelets require room temperature storage with agitation to maintain viability and allow gas exchange. Agitation does not prevent bacterial growth, activate platelets, or increase the count.

Question 40Blood Banking

Which of the following best describes the function of antihuman globulin reagent?

  1. It lyses red cells directly
  2. It bridges antibody-coated red cells to produce visible agglutination Correct answer.
  3. It enhances complement fixation
  4. It neutralizes free antibody in serum

Explanation

Antihuman globulin contains antibodies against human immunoglobulins and complement, bridging sensitized red cells to create visible agglutination. It does not directly lyse cells, neutralize antibody, or primarily enhance complement fixation.

Question 41Blood Banking

A patient's antibody screen is positive at the antiglobulin phase but negative at immediate spin. What does this pattern suggest?

  1. An IgG antibody reactive at 37 degrees C Correct answer.
  2. A clerical error
  3. An IgM antibody reactive at room temperature
  4. An ABO incompatibility

Explanation

Reactivity only at the antiglobulin phase indicates an IgG antibody that sensitizes red cells at 37 degrees C. IgM antibodies typically react at immediate spin and room temperature, and ABO incompatibility is usually detected at immediate spin.

Question 42Blood Banking

Which of the following is a common cause of a positive direct antiglobulin test in a patient with autoimmune hemolytic anemia?

  1. ABO incompatibility in donor units
  2. Elevated hemoglobin
  3. Cold agglutinins in the serum only
  4. Warm IgG autoantibodies bound to red cells Correct answer.

Explanation

Warm autoimmune hemolytic anemia is characterized by IgG autoantibodies bound to red cells in vivo, producing a positive DAT. Cold agglutinins may also cause a positive DAT but are typically IgM and complement-mediated, and elevated hemoglobin is unrelated.

Question 43Blood Banking

Which red cell antigen system is most important to match for patients who require chronic transfusion therapy to prevent alloimmunization?

  1. Lewis and P
  2. I and i
  3. Rh and Kell Correct answer.
  4. MNS and Lutheran

Explanation

Patients on chronic transfusion are often matched for Rh (including C, c, E, e) and Kell antigens to reduce alloimmunization. Lewis, P, I, and i are not typically the focus of extended matching.

Question 44Blood Banking

What is the primary purpose of leukoreduction of blood products?

  1. To increase red cell survival
  2. To prevent ABO incompatibility
  3. To reduce febrile nonhemolytic transfusion reactions and CMV transmission Correct answer.
  4. To improve oxygen carrying capacity

Explanation

Leukoreduction removes white cells to decrease the risk of febrile nonhemolytic reactions and transmission of cell-associated viruses such as CMV. It does not increase red cell survival, prevent ABO incompatibility, or improve oxygen carrying capacity.

Question 45Blood Banking

A patient with group O blood receives a group A unit of red cells. Which reaction is most likely to occur?

  1. Acute hemolytic transfusion reaction Correct answer.
  2. Allergic reaction
  3. Febrile nonhemolytic reaction
  4. Transfusion-related acute lung injury

Explanation

Group O recipients have anti-A and anti-B antibodies that can cause acute intravascular hemolysis when given group A red cells. Febrile, allergic, and TRALI reactions are not specifically predicted by this ABO mismatch.

Question 46Blood Banking

Which of the following best describes the principle of the gel microcolumn technique in blood banking?

  1. Gel enhances complement binding
  2. Red cells are trapped in gel particles after agglutination Correct answer.
  3. Red cells are lysed by gel enzymes
  4. Gel replaces the need for antiglobulin reagent

Explanation

In gel testing, agglutinated red cells are trapped in the gel column while unagglutinated cells pass through, allowing detection of agglutination. The gel does not lyse cells, enhance complement, or eliminate the need for antiglobulin in IAT testing.

Question 47Blood Banking

A patient's serum agglutinates all panel cells equally at room temperature, including autologous cells. What is the most likely explanation?

  1. A warm autoantibody
  2. An alloantibody to a high-incidence antigen
  3. A cold autoantibody Correct answer.
  4. An ABO incompatibility

Explanation

Panreactivity at room temperature with autologous cells suggests a cold autoantibody, such as anti-I. Alloantibodies to high-incidence antigens typically do not react with autologous cells, and ABO incompatibility would not react with autologous cells.

Question 48Blood Banking

Which of the following is the most appropriate action when a patient has a positive antibody screen and a history of anti-Jka?

  1. Delay transfusion until the antibody disappears
  2. Transfuse group O negative units without crossmatch
  3. Select Jka-negative units and perform a crossmatch Correct answer.
  4. Select Jka-positive units with a negative crossmatch

Explanation

Patients with a history of anti-Jka should receive Jka-negative units to prevent a delayed hemolytic reaction, and a crossmatch should be performed. Jka-positive units could react, and transfusion should not be delayed unnecessarily.

Question 49Blood Banking

A patient's forward typing shows group AB, but the reverse typing shows agglutination with A1 cells and B cells. What is the most likely explanation?

  1. The patient is group B
  2. The patient has an acquired B antigen or a subgroup with weak antibody production Correct answer.
  3. The patient is group A
  4. The patient is group O

Explanation

Forward typing as AB with reverse reactivity against A and B cells suggests a discrepancy such as an acquired B antigen or a subgroup with unexpected antibodies. Group O, A, or B would not produce this forward typing pattern.

Question 50Blood Banking

Which of the following is a key consideration when selecting blood for a patient with sickle cell disease who requires chronic transfusion?

  1. Transfusion of the oldest available units
  2. Use of group O whole blood only
  3. Avoidance of leukoreduced products
  4. Extended antigen matching for Rh and Kell to reduce alloimmunization Correct answer.

Explanation

Patients with sickle cell disease are at high risk for alloimmunization and often receive extended antigen-matched (Rh and Kell) red cells. Whole blood, non-leukoreduced products, and older units are not preferred.