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ASCP MLT practice questions

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Question 1Blood Bank

In a group A individual, what reaction is expected in the reverse (serum) typing?

  1. Agglutination with both A1 and B cells
  2. No agglutination with either cell
  3. Agglutination with A1 cells only
  4. Agglutination with B cells only Correct answer.

Explanation

Group A individuals have anti-B in their serum, so reverse typing shows agglutination with B cells and no agglutination with A1 cells. Forward typing with anti-A is positive and anti-B is negative.

Question 2Blood Bank

What is the maximum storage time for red blood cells collected in CPDA-1 at 1-6 C?

  1. 42 days
  2. 21 days
  3. 45 days
  4. 35 days Correct answer.

Explanation

CPDA-1 preserves red blood cells for 35 days at 1-6 C. Additive solutions such as AS-1 extend storage to 42 days.

Question 3Blood Bank

Which blood component must be stored frozen at -18 C or colder?

  1. Fresh frozen plasma Correct answer.
  2. Washed red blood cells
  3. Packed red blood cells
  4. Platelet concentrate

Explanation

Fresh frozen plasma is stored frozen at -18 C or colder to preserve labile coagulation factors. Once thawed, it is stored at 1-6 C and used within 24 hours.

Question 4Blood Bank

What is the required storage condition for platelet concentrates?

  1. -18 C or colder
  2. 20-24 C with continuous agitation Correct answer.
  3. 1-6 C without agitation
  4. 1-6 C with agitation

Explanation

Platelets require storage at 20-24 C with continuous agitation to maintain viability and prevent clumping. Refrigeration impairs platelet function and reduces circulation time.

Question 5Blood Bank

Which immunoglobulin class is most commonly responsible for an immediate hemolytic transfusion reaction due to ABO incompatibility?

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

Explanation

ABO antibodies are naturally occurring IgM antibodies that activate complement and cause rapid intravascular hemolysis. IgG antibodies are more typically associated with delayed hemolytic reactions.

Question 6Blood Bank

What is the first action when a transfusion reaction is suspected?

  1. Repeat the crossmatch
  2. Notify the blood supplier
  3. Stop the transfusion and verify the patient's identity Correct answer.
  4. Perform a direct antiglobulin test immediately

Explanation

The transfusion must be stopped immediately and the patient identity and unit labels verified to rule out a clerical error. Further testing follows after patient safety is addressed.

Question 7Blood Bank

Which blood group system antibodies are naturally occurring and typically react at room temperature?

  1. Kell
  2. Rh
  3. Duffy
  4. ABO Correct answer.

Explanation

ABO antibodies are naturally occurring IgM antibodies that react at room temperature or immediate spin. Rh, Kell, and Duffy antibodies are generally immune-stimulated IgG antibodies that react at 37 C or AHG phase.

Question 8Blood Bank

Which preservative solution allows red blood cell storage for 42 days at 1-6 C?

  1. Heparin
  2. AS-1 Correct answer.
  3. ACD
  4. CPDA-1

Explanation

Additive solutions such as AS-1 extend red cell storage to 42 days. CPDA-1 supports 35-day storage, and ACD supports 21 days.

Question 9Blood Bank

A patient's forward typing shows 4+ agglutination with anti-A and no agglutination with anti-B. The reverse typing shows agglutination with A1 cells but not with B cells. What is the most likely explanation?

  1. A2 subgroup with anti-A1 Correct answer.
  2. Group B with anti-A1
  3. A1 subgroup with anti-A2
  4. Group AB with anti-A1

Explanation

A2 individuals can produce anti-A1, which agglutinates A1 cells but not A2 cells. The forward typing remains group A because A2 red cells still carry A antigen.

Question 10Blood Bank

Weak D testing is performed when the initial anti-D typing reaction is:

  1. strongly positive at immediate spin
  2. negative or weak at immediate spin Correct answer.
  3. equivocal with anti-B
  4. positive only at the AHG phase

Explanation

Weak D testing is indicated when the initial anti-D test is negative or weak, to detect weak expression of the D antigen. This helps prevent immunization of a weak D patient with D-positive blood.

Question 11Blood Bank

Which antibody commonly demonstrates a dosage effect, reacting more strongly with homozygous cells?

  1. Anti-K
  2. Anti-D
  3. Anti-Lua
  4. Anti-Jka Correct answer.

Explanation

Antibodies in the Kidd system, such as anti-Jka, often show dosage and react more strongly with cells homozygous for the antigen. Anti-K and anti-D usually react well with both heterozygous and homozygous cells.

Question 12Blood Bank

What is the most common cause of a febrile nonhemolytic transfusion reaction?

  1. IgA deficiency in the recipient
  2. Recipient antibodies to donor leukocyte antigens Correct answer.
  3. Bacterial contamination of the unit
  4. Donor antibodies to recipient red cells

Explanation

Febrile nonhemolytic reactions most often result from recipient antibodies directed against donor leukocytes, including HLA antigens, releasing cytokines. Leukoreduction reduces the frequency of these reactions.

Question 13Blood Bank

Which component is most appropriate for a patient with severe IgA deficiency and anti-IgA who requires red cell transfusion?

  1. Irradiated red blood cells
  2. Fresh frozen plasma
  3. Leukoreduced red blood cells
  4. Washed red blood cells Correct answer.

Explanation

Washing removes residual plasma proteins, including IgA, and reduces the risk of an anaphylactic reaction in patients with anti-IgA. IgA-deficient plasma or components from IgA-deficient donors may also be used when available.

Question 14Blood Bank

Which component is indicated for a patient with von Willebrand disease who does not respond to desmopressin?

  1. Platelets
  2. Washed red blood cells
  3. Granulocyte concentrate
  4. Cryoprecipitate Correct answer.

Explanation

Cryoprecipitate is rich in von Willebrand factor and fibrinogen and can be used when desmopressin is ineffective. Factor concentrates are preferred when available.

Question 15Blood Bank

What is the purpose of irradiating blood components?

  1. Prevent cytomegalovirus transmission
  2. Prevent febrile nonhemolytic reactions
  3. Prevent transfusion-associated graft-versus-host disease Correct answer.
  4. Prevent bacterial growth

Explanation

Irradiation inactivates donor T lymphocytes, preventing transfusion-associated graft-versus-host disease in susceptible recipients. It does not sterilize the unit or prevent most other transfusion reactions.

Question 16Blood Bank

Which red cell antigen matching is recommended for a patient with sickle cell disease receiving chronic transfusions?

  1. ABO only
  2. ABO and K only
  3. ABO and D only
  4. ABO plus C, E, and K Correct answer.

Explanation

Extended matching for Rh antigens C and E and for Kell (K) reduces the risk of alloimmunization in chronically transfused sickle cell patients. ABO and D matching alone is insufficient.

Question 17Blood Bank

Which test detects antibodies coating a patient's red cells in vivo?

  1. Immediate spin crossmatch
  2. Indirect antiglobulin test
  3. Antibody screening test
  4. Direct antiglobulin test Correct answer.

Explanation

The direct antiglobulin test detects antibodies or complement bound to red cells in the patient's circulation. The indirect antiglobulin test detects antibodies in serum or plasma.

Question 18Blood Bank

When a patient's ABO type is unknown and red cells must be released emergently, which component is given?

  1. Group AB red blood cells
  2. Group O red blood cells Correct answer.
  3. Group A red blood cells
  4. Group AB plasma

Explanation

Group O red blood cells are used for emergency release when the recipient's ABO type is unknown because they lack A and B antigens. Group AB plasma is used when plasma is needed emergently.

Question 19Blood Bank

Which antibody is most commonly implicated in a delayed hemolytic transfusion reaction?

  1. Anti-Jka Correct answer.
  2. Anti-I
  3. Anti-P1
  4. Anti-Lea

Explanation

Delayed hemolytic reactions often involve IgG alloantibodies such as anti-Jka that were not detectable before transfusion. The antibody becomes detectable as the anamnestic response develops.

Question 20Blood Bank

A patient's antibody screen is negative at immediate spin and 37 C but positive at the AHG phase. Which antibody class is most likely present?

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

Explanation

IgG antibodies typically do not agglutinate red cells at immediate spin and require the antiglobulin phase for detection. IgM antibodies usually react at room temperature or immediate spin.

Question 21Blood Bank

A postpartum Rh-negative woman has a Kleihauer-Betke result of 1.5% fetal cells. Assuming a maternal blood volume of 5000 mL and that each 300 mcg vial of Rh immune globulin covers 30 mL of fetal whole blood, how many vials should be given?

  1. 2 vials
  2. 4 vials
  3. 3 vials Correct answer.
  4. 1 vial

Explanation

The fetal bleed volume is 1.5% of 5000 mL, or 75 mL. Dividing 75 mL by 30 mL per vial gives 2.5, which is rounded up to 3 vials.

Question 22Blood Bank

A patient with warm autoimmune hemolytic anemia has a positive DAT and panreactive serum. Which procedure is most appropriate to identify an underlying alloantibody?

  1. Polyethylene glycol enhancement
  2. Autologous adsorption Correct answer.
  3. Heat elution
  4. Immediate spin crossmatch

Explanation

Autologous adsorption removes the warm autoantibody from the patient's serum, allowing any underlying alloantibody to be detected. If the patient was recently transfused, allogeneic adsorption may be required.

Question 23Blood Bank

A patient develops fever, hypotension, hypoxemia, and bilateral pulmonary infiltrates within 6 hours of a transfusion. What is the most likely diagnosis?

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

Explanation

Transfusion-related acute lung injury presents with acute hypoxemia and bilateral infiltrates within 6 hours of transfusion, often with fever and hypotension. It is distinct from circulatory overload, which is associated with volume excess and hypertension.

Question 24Blood Bank

How long may deglycerolized red blood cells be stored at 1-6 C after thawing and washing?

  1. 10 days
  2. 72 hours
  3. 6 hours
  4. 24 hours Correct answer.

Explanation

Once frozen red cells are deglycerolized, they are stored at 1-6 C and must be used within 24 hours. This limits the logistics of using frozen red cell units.

Question 25Blood Bank

A patient develops high fever, hypotension, and shock during a platelet transfusion. What is the most appropriate immediate action?

  1. Stop the transfusion and culture the unit and patient Correct answer.
  2. Administer diuretics and continue the transfusion
  3. Perform a Kleihauer-Betke test
  4. Continue the transfusion and give antipyretics

Explanation

These findings suggest a septic transfusion reaction from bacterial contamination. The transfusion must be stopped, the patient treated, and the unit and patient cultured to identify the organism.

Question 26Blood Bank

Platelet concentrates must be stored under which of the following conditions?

  1. 20-24 C with continuous agitation Correct answer.
  2. -18 C or colder
  3. 20-24 C without agitation
  4. 1-6 C with continuous agitation

Explanation

Platelets require room temperature storage (approximately 20-24 C) with continuous gentle agitation to maintain pH and prevent clumping, which supports a shelf life of about 5 days. Refrigeration causes platelet shape change and loss of function, and freezing without a cryoprotectant destroys them.

Question 27Blood Bank

Fresh frozen plasma is thawed and then kept refrigerated at 1-6 C. Within what period must it be transfused?

  1. Within 12 hours
  2. Within 4 hours
  3. Within 24 hours Correct answer.
  4. Within 72 hours

Explanation

Once thawed, fresh frozen plasma is considered a liquid component with labile coagulation factors; if held at 1-6 C it must be transfused within 24 hours. After that point the labile factors, particularly factor VIII, have deteriorated and the unit must be discarded.

Question 28Blood Bank

A patient's serum agglutinates all reagent red cells tested at room temperature and at the antihuman globulin phase. After the serum is treated with dithiothreitol, the reactivity disappears. This result indicates that the responsible antibody belongs to which class?

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

Explanation

Dithiothreitol reduces the disulfide bonds that hold immunoglobulin subunits together, destroying the agglutinating ability of IgM (and IgA) while leaving IgG activity intact. Loss of reactivity after treatment therefore points to an IgM antibody, which is typical of cold-reacting antibodies such as anti-I.

Question 29Chemistry

Which blood collection tube is preferred for glucose testing because it inhibits glycolysis by red blood cells?

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

Explanation

Sodium fluoride blocks the enolase step of glycolysis, so glucose remains stable for hours in an unseparated gray-top tube. Tubes without an antiglycolytic agent allow glucose to fall by roughly 5–7% per hour at room temperature.

Question 30Chemistry

Which analyte is routinely measured in serum to estimate glomerular filtration rate?

  1. Amylase
  2. Uric acid
  3. Creatinine Correct answer.
  4. Urea nitrogen

Explanation

Creatinine is produced at a relatively constant rate from muscle creatine and is cleared almost entirely by glomerular filtration, so its concentration rises as GFR falls. Urea is also filtered but is reabsorbed by the tubules and varies with hydration and protein intake.

Question 31Chemistry

What is the reference interval for arterial blood pH in a healthy adult?

  1. 7.30–7.35
  2. 7.20–7.30
  3. 7.35–7.45 Correct answer.
  4. 7.45–7.55

Explanation

The normal arterial pH range is 7.35 to 7.45, reflecting the balance between carbon dioxide tension and bicarbonate. Values below 7.35 indicate acidemia and values above 7.45 indicate alkalemia.

Question 32Chemistry

Which enzyme is considered the most pancreas-specific marker of acute pancreatitis?

  1. Creatine kinase
  2. Alkaline phosphatase
  3. Lipase Correct answer.
  4. Aspartate aminotransferase

Explanation

Lipase is produced primarily by the pancreas and remains elevated longer than amylase, giving it greater specificity and sensitivity for pancreatic injury. Alkaline phosphatase, creatine kinase, and aminotransferases arise from other tissues.

Question 33Chemistry

Hemoglobin A1c reflects the average blood glucose concentration over approximately what period of time?

  1. The preceding 24 hours
  2. The preceding 6 to 12 hours
  3. The preceding 2 to 3 months Correct answer.
  4. The preceding 12 months

Explanation

Glucose attaches irreversibly to hemoglobin over the roughly 120-day lifespan of the erythrocyte, so HbA1c represents a weighted average of glycemia over the preceding two to three months. It is not a measure of acute glucose control.

Question 34Chemistry

Which ion is the principal intracellular cation in the body?

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

Explanation

Potassium is concentrated inside cells, where it serves as the main intracellular cation, while sodium is the dominant extracellular cation. The sodium-potassium ATPase maintains this gradient.

Question 35Chemistry

Total calcium results are most affected by the concentration of which plasma protein?

  1. Albumin Correct answer.
  2. Haptoglobin
  3. Fibrinogen
  4. Transferrin

Explanation

Roughly 40% of circulating calcium is bound to albumin, so a low albumin lowers total calcium without changing the physiologically active ionized fraction. Laboratories therefore report albumin-corrected calcium values.

Question 36Chemistry

Which specimen is preferred for blood gas analysis?

  1. Serum from a plain clot tube
  2. Citrated plasma
  3. Heparinized arterial whole blood Correct answer.
  4. EDTA whole blood

Explanation

Arterial whole blood collected in heparin is used because heparin is the only anticoagulant that does not meaningfully alter pH, pCO2, or pO2, and arterial blood directly reflects oxygenation. The sample must be analyzed promptly and kept anaerobic.

Question 37Chemistry

A patient has a sodium of 140 mmol/L, chloride of 104 mmol/L, and bicarbonate of 24 mmol/L. What is the anion gap?

  1. 12 mmol/L Correct answer.
  2. 20 mmol/L
  3. 16 mmol/L
  4. 8 mmol/L

Explanation

The anion gap is calculated as sodium minus the sum of chloride and bicarbonate, so 140 − (104 + 24) = 12 mmol/L. This value falls within the usual reference interval of about 8 to 16 mmol/L.

Question 38Chemistry

Which marker is most specific for myocardial injury?

  1. Troponin I Correct answer.
  2. Total creatine kinase
  3. Aspartate aminotransferase
  4. Lactate dehydrogenase

Explanation

Cardiac troponin I and T are expressed only in myocardium, so their release is highly specific for myocardial necrosis and they remain elevated for days. Older markers such as CK, LD, and AST also arise from skeletal muscle, liver, and red cells.

Question 39Chemistry

A patient has an elevated alkaline phosphatase together with an elevated gamma-glutamyl transferase. This combination most likely indicates disease of which origin?

  1. Bone
  2. Skeletal muscle
  3. Intravascular hemolysis
  4. Hepatobiliary Correct answer.

Explanation

Gamma-glutamyl transferase is present in hepatocytes and biliary epithelium, so a concurrent rise confirms that an elevated alkaline phosphatase comes from the liver or biliary tree rather than bone. Bone disease raises alkaline phosphatase without raising GGT.

Question 40Chemistry

In a patient with hemolytic anemia, which bilirubin fraction is predominantly increased in serum?

  1. Conjugated bilirubin
  2. Bilirubin glucuronide
  3. Delta bilirubin
  4. Unconjugated bilirubin Correct answer.

Explanation

Accelerated red cell destruction delivers excess heme to the liver, and the conjugating capacity is exceeded, so unconjugated (indirect) bilirubin accumulates. Conjugated fractions rise mainly with cholestasis or hepatocellular disease.

Question 41Chemistry

When should a trough specimen be collected for therapeutic drug monitoring of a drug given at fixed intervals?

  1. At the midpoint of the dosing interval
  2. At any convenient time of day
  3. Thirty minutes after a dose is given
  4. Immediately before the next scheduled dose Correct answer.

Explanation

The trough is drawn just before the next dose, when the concentration has reached its lowest steady-state point, allowing comparison with a defined reference range. Timing must be consistent because concentrations change substantially across a dosing interval.

Question 42Chemistry

A narrow, dense band in the gamma region of serum protein electrophoresis most suggests which condition?

  1. Acute-phase inflammation
  2. Monoclonal gammopathy Correct answer.
  3. Iron-deficiency anemia
  4. Nephrotic syndrome

Explanation

A restricted, sharp band indicates a single clone of immunoglobulin-producing cells, as seen in multiple myeloma or other monoclonal gammopathies. Polyclonal increases produce a broad, diffuse gamma rise.

Question 43Chemistry

Cerebrospinal fluid glucose in a healthy fasting patient is approximately what proportion of the simultaneous serum glucose?

  1. About 60% Correct answer.
  2. About 20%
  3. About 85%
  4. About 40%

Explanation

CSF glucose is normally about 60% of the plasma value, reflecting facilitated transport across the blood-brain barrier. Values below roughly 40% of serum suggest bacterial meningitis or other causes of increased CSF glycolysis.

Question 44Chemistry

Gout results from tissue deposition of crystals composed of which substance?

  1. Calcium pyrophosphate
  2. Cholesterol
  3. Monosodium urate Correct answer.
  4. Calcium oxalate

Explanation

Hyperuricemia leads to deposition of monosodium urate crystals in joints and soft tissue, producing the acute inflammatory attack of gout. Serum uric acid is measured to support the diagnosis and guide therapy.

Question 45Chemistry

Which formula is used to estimate serum osmolality from sodium, glucose, and urea nitrogen?

  1. 2 × Na + glucose/2.8 + BUN/18
  2. Na + glucose/18 + BUN/2.8
  3. 2 × Na + glucose/18 + BUN/2.8 Correct answer.
  4. Na + glucose + BUN

Explanation

Sodium contributes with its accompanying anions, so it is doubled, and glucose and urea are converted from mg/dL to mmol/L by dividing by their molecular weights (18 and 2.8). The result is compared with a measured osmolality to calculate the osmolal gap.

Question 46Chemistry

When blood pH rises in alkalosis, the ionized calcium concentration typically does what?

  1. Remains unchanged
  2. Becomes undetectable
  3. Decreases Correct answer.
  4. Increases

Explanation

Hydrogen ions compete with calcium for albumin binding sites, so in alkalosis fewer hydrogen ions are available, more calcium binds to albumin, and the ionized fraction falls. This can produce tetany despite a normal total calcium.

Question 47Chemistry

According to Beer's law, absorbance is directly proportional to analyte concentration only when which condition is met?

  1. The wavelength is scanned continuously during reading
  2. The light path length and molar absorptivity are constant Correct answer.
  3. The solution is visibly turbid
  4. The cuvette path length is varied between samples

Explanation

Beer's law states that absorbance equals molar absorptivity times path length times concentration, so linearity with concentration requires that the absorptivity and the light path remain fixed. Turbidity and stray light cause deviations from linearity.

Question 48Chemistry

Which condition characteristically raises blood urea nitrogen out of proportion to creatinine?

  1. Early pregnancy
  2. Rhabdomyolysis
  3. Acute glomerulonephritis
  4. Upper gastrointestinal bleeding Correct answer.

Explanation

Digested blood in the gut provides a large protein load that the liver converts to urea, so BUN rises while creatinine, which depends on muscle mass and filtration, changes little. Dehydration and catabolic states produce a similar pattern.

Question 49Chemistry

A patient has total cholesterol 250 mg/dL, HDL cholesterol 50 mg/dL, and triglycerides 150 mg/dL. Using the Friedewald formula, what is the LDL cholesterol?

  1. 200 mg/dL
  2. 120 mg/dL
  3. 230 mg/dL
  4. 170 mg/dL Correct answer.

Explanation

Friedewald LDL equals total cholesterol minus HDL minus triglycerides divided by 5, so 250 − 50 − (150/5) = 170 mg/dL. The calculation assumes triglycerides are below about 400 mg/dL.

Question 50Chemistry

Which tumor marker is used to monitor adenocarcinoma of the prostate?

  1. Prostate-specific antigen Correct answer.
  2. Alpha-fetoprotein
  3. Carcinoembryonic antigen
  4. CA 125

Explanation

Prostate-specific antigen is a serine protease produced by prostatic epithelium, and serial measurements are used to follow response to therapy. Neither alpha-fetoprotein, CEA, nor CA 125 is prostate specific.