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ABPath Combined AP/CP Primary Certification study materials
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ABPath Combined AP/CP Primary Certification practice questions

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Question 1Clinical Pathology: Blood Banking/Transfusion Medicine

Which ABO group red blood cells can be transfused to a recipient of any ABO type without causing ABO incompatibility?

  1. Group A
  2. Group B
  3. Group O Correct answer.
  4. Group AB

Explanation

Group O red cells lack both A and B antigens, so recipient anti-A and anti-B cannot bind to them. Group AB plasma is the universal plasma donor, but AB red cells express both A and B antigens and are the universal recipient, not universal donor, for red cells.

Question 2Clinical Pathology: Blood Banking/Transfusion Medicine

Fresh frozen plasma must be maintained at which of the following temperatures during storage?

  1. 37 °C
  2. 2 to 6 °C
  3. −18 °C or colder Correct answer.
  4. 20 to 24 °C

Explanation

Plasma is frozen within 8 hours of collection (24 hours for FP24) and stored at −18 °C or colder for up to 12 months. It is then thawed at 30 to 37 °C and used within 24 hours.

Question 3Clinical Pathology: Blood Banking/Transfusion Medicine

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

  1. 2 to 6 °C with continuous agitation
  2. 22 °C without agitation
  3. −18 °C or colder
  4. 20 to 24 °C with agitation Correct answer.

Explanation

Platelets are stored at 20 to 24 °C with continuous gentle agitation for up to 5 to 7 days. Agitation maintains pH and oxygen delivery, preserving platelet viability.

Question 4Clinical Pathology: Blood Banking/Transfusion Medicine

Cryoprecipitate is most commonly transfused to replace which of the following?

  1. Fibrinogen Correct answer.
  2. Protein C
  3. Factor IX
  4. Factor VII

Explanation

Cryoprecipitate is rich in fibrinogen, factor VIII, von Willebrand factor, factor XIII, and fibronectin. Its most common current indication is replacement of fibrinogen in hypofibrinogenemic bleeding or in massive transfusion.

Question 5Clinical Pathology: Blood Banking/Transfusion Medicine

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

  1. Bacterial contamination of the unit
  2. Recipient anti-HLA antibodies Correct answer.
  3. Acute ABO incompatibility
  4. Severe IgA deficiency

Explanation

Febrile nonhemolytic reactions most often result from recipient antibodies directed against donor leukocyte antigens, or from cytokines that accumulate in stored components. Prestorage leukoreduction substantially reduces their frequency.

Question 6Clinical Pathology: Blood Banking/Transfusion Medicine

A trauma patient in hemorrhagic shock requires immediate transfusion, but compatibility testing cannot be completed in time. Which product should be released?

  1. Crossmatched red cells
  2. Group AB red cells
  3. O Rh-negative red cells Correct answer.
  4. Group A plasma

Explanation

Uncrossmatched emergency release uses group O red cells; Rh-negative units are preferred for women of childbearing potential to prevent anti-D alloimmunization. Group O red cells lack A and B antigens and therefore pose the lowest risk to recipients of unknown type.

Question 7Clinical Pathology: Blood Banking/Transfusion Medicine

Gamma irradiation of cellular blood components is performed primarily to do which of the following?

  1. Prevent febrile nonhemolytic reactions
  2. Sterilize the unit against bacteria
  3. Prevent transfusion-associated GVHD Correct answer.
  4. Reduce the risk of TRALI

Explanation

Irradiation inactivates donor T lymphocytes, which prevents engraftment and transfusion-associated graft-versus-host disease in at-risk recipients. It does not sterilize the unit, and it has no effect on plasma antibodies or cytokines.

Question 8Clinical Pathology: Blood Banking/Transfusion Medicine

Rh immune globulin is administered to an RhD-negative mother primarily to prevent which of the following?

  1. Neonatal alloimmune thrombocytopenia
  2. Transfusion-associated GVHD
  3. Maternal anti-D alloimmunization Correct answer.
  4. ABO hemolytic disease of the newborn

Explanation

Rh immune globulin clears RhD-positive fetal red cells before the maternal immune system can mount a primary response, preventing formation of anti-D. This in turn protects subsequent RhD-positive pregnancies from hemolytic disease.

Question 9Clinical Pathology: Blood Banking/Transfusion Medicine

Which red cell antibody is best known for evanescence, so that a previously sensitized patient may have a negative antibody screen and later develop a delayed hemolytic transfusion reaction?

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

Explanation

Antibodies of the Kidd system, especially anti-Jka, notoriously fall below the limit of detection and then rebound after transfusion. This anamnestic response produces a delayed hemolytic reaction, often with a positive DAT and falling hemoglobin days after transfusion.

Question 10Clinical Pathology: Blood Banking/Transfusion Medicine

A 72-year-old man with heart failure develops dyspnea, hypertension, and hypoxemia 2 hours after receiving two units of red cells; his BNP is elevated. Which is the most likely diagnosis?

  1. Circulatory overload Correct answer.
  2. Acute hemolysis
  3. TRALI
  4. Septic reaction

Explanation

Hypertension, elevated BNP, jugular venous distension, and dyspnea shortly after transfusion indicate transfusion-associated circulatory overload. TRALI instead presents with hypotension, normal filling pressures, and a normal or low BNP.

Question 11Clinical Pathology: Blood Banking/Transfusion Medicine

Which finding best supports a diagnosis of transfusion-related acute lung injury?

  1. Positive DAT with falling haptoglobin
  2. Elevated BNP with jugular venous distension
  3. Bilateral infiltrates within 6 hours without overload Correct answer.
  4. Onset 24 to 48 hours after transfusion

Explanation

TRALI is defined by new bilateral pulmonary infiltrates developing within 6 hours of transfusion, with hypoxemia and no evidence of circulatory overload. Donor antibodies against HLA or neutrophil antigens are frequently implicated.

Question 12Clinical Pathology: Blood Banking/Transfusion Medicine

A patient with undetectable serum IgA and circulating anti-IgA antibodies requires red cell transfusion. Which component is most appropriate?

  1. Leukoreduced red cells
  2. Standard red cells
  3. Irradiated red cells
  4. Washed red cells Correct answer.

Explanation

IgA-deficient patients with anti-IgA are at risk for anaphylaxis from plasma proteins present in cellular components. Washed red cells remove residual plasma and reduce this risk; IgA-deficient plasma is used when plasma products are needed.

Question 13Clinical Pathology: Blood Banking/Transfusion Medicine

Which metabolic abnormality is most characteristic of massive transfusion and results from the citrate anticoagulant?

  1. Metabolic acidosis
  2. Hypokalemia
  3. Ionized hypocalcemia Correct answer.
  4. Hypernatremia

Explanation

Citrate chelates calcium, so rapid large-volume transfusion can produce ionized hypocalcemia with paresthesias, tetany, and cardiac dysfunction. Monitoring and calcium replacement are standard in massive transfusion protocols.

Question 14Clinical Pathology: Blood Banking/Transfusion Medicine

In a neonate with severe hemolytic disease of the newborn, the primary purpose of exchange transfusion is to do which of the following?

  1. Provide functional platelets
  2. Correct anemia by adding adult red cells
  3. Neutralize maternal antibody with RhIG
  4. Remove bilirubin and antibody-coated red cells Correct answer.

Explanation

Exchange transfusion removes bilirubin and maternal antibody-coated neonatal red cells while replacing them with compatible donor red cells. This lowers the bilirubin load and interrupts ongoing hemolysis in severe disease.

Question 15Clinical Pathology: Blood Banking/Transfusion Medicine

A donor unit types as negative with anti-D at immediate spin but shows agglutination with anti-D at the antiglobulin phase. How should the unit be labeled?

  1. RhD-positive only if the recipient is RhD-positive
  2. RhD variant requiring genotyping before labeling
  3. RhD-negative, suitable for any recipient
  4. RhD-positive Correct answer.

Explanation

Donor units with weak D expression detected only by the indirect antiglobulin technique are labeled RhD-positive. This conservative approach prevents transfusing a unit that could immunize an RhD-negative recipient.

Question 16Clinical Pathology: Blood Banking/Transfusion Medicine

A patient was transfused 2 months ago and now requires red cell transfusion. How long is the pretransfusion sample valid for compatibility testing?

  1. 30 days
  2. 7 days
  3. 72 hours Correct answer.
  4. 24 hours

Explanation

When a patient has been transfused or pregnant within the preceding 3 months, the pretransfusion sample is valid for only 72 hours. This limits the risk of missing a newly formed antibody that could cause a delayed hemolytic reaction.

Question 17Clinical Pathology: Blood Banking/Transfusion Medicine

Prestorage leukoreduction of red cell units most directly reduces the risk of which of the following?

  1. Bacterial contamination and TACO
  2. TRALI and hyperkalemia
  3. Febrile reactions and CMV transmission Correct answer.
  4. Alloimmunization to RhD and ABO hemolysis

Explanation

Removing donor leukocytes decreases cytokine accumulation and recipient anti-HLA responses, lowering febrile nonhemolytic reaction rates. Leukoreduction also reduces transmission of CMV, which resides within white cells.

Question 18Clinical Pathology: Blood Banking/Transfusion Medicine

Which red cell antibody is generally considered clinically insignificant and does not require antigen-negative units?

  1. Anti-Fya
  2. Anti-Lea Correct answer.
  3. Anti-K
  4. Anti-Jka

Explanation

Lewis antibodies are usually IgM, react at room temperature, do not cross the placenta, and rarely cause in vivo red cell destruction. They are therefore generally disregarded when selecting units for transfusion.

Question 19Clinical Pathology: Blood Banking/Transfusion Medicine

A patient with leukemia has poor platelet increments at both 1 hour and 24 hours after transfusion, with no splenomegaly, fever, or bleeding. What is the most likely cause?

  1. Bacterial contamination of the units
  2. Disseminated intravascular coagulation
  3. Sequestration in the spleen
  4. HLA alloimmunization Correct answer.

Explanation

Poor increments at 1 hour indicate immune-mediated destruction, most often from anti-HLA antibodies induced by prior transfusions or pregnancy. Refractoriness from splenomegaly, fever, or sepsis typically shows a reduced 24-hour increment with a preserved 1-hour increment.

Question 20Clinical Pathology: Blood Banking/Transfusion Medicine

Which statement best describes ABO hemolytic disease of the newborn?

  1. It affects RhD-positive infants of RhD-negative mothers
  2. A group A infant of a group O mother Correct answer.
  3. It most often causes hydrops fetalis
  4. It requires exchange transfusion in most cases

Explanation

ABO hemolytic disease occurs when IgG anti-A or anti-B from a group O mother crosses the placenta and coats group A or B fetal red cells. It is usually mild and can affect the first pregnancy, in contrast to RhD disease.

Question 21Clinical Pathology: Blood Banking/Transfusion Medicine

A patient's forward type agglutinates with both anti-A and anti-B reagents, while the reverse type agglutinates with A1 cells but not with B cells. What is the most likely explanation?

  1. Cold autoagglutinin with anti-I specificity
  2. Rouleaux formation
  3. Acquired B phenotype
  4. A2B phenotype with anti-A1 Correct answer.

Explanation

A2B individuals can produce a naturally occurring anti-A1 that reacts with A1 reagent cells while the forward type remains AB. The discrepancy is resolved by testing with A2 cells and confirming the subgroup.

Question 22Clinical Pathology: Blood Banking/Transfusion Medicine

Methyldopa causes immune hemolytic anemia through which mechanism?

  1. Induction of a red cell autoantibody resembling anti-Rh Correct answer.
  2. Immune complex formation with complement activation
  3. Drug adsorption to the red cell membrane with anti-drug antibodies
  4. Direct oxidative membrane damage

Explanation

Methyldopa induces a warm autoantibody, often with Rh-related specificity, producing an IgG-positive direct antiglobulin test. Hemolysis is usually mild and resolves after the drug is discontinued.

Question 23Clinical Pathology: Blood Banking/Transfusion Medicine

A patient's serum reacts with all panel cells at the antiglobulin phase, the autocontrol is positive, and the DAT is positive for IgG. Which technique is most appropriate to detect a possible underlying alloantibody?

  1. Elute the antibody from the patient's cells and test the eluate
  2. Allogeneic adsorption with phenotype-selected cells Correct answer.
  3. Enzyme treatment of the patient's serum
  4. Repeat the panel at immediate spin

Explanation

Allogeneic adsorption uses selected donor cells to remove the panreactive warm autoantibody, allowing any underlying alloantibody to be identified. Autoadsorption is preferred when the patient has not been recently transfused.

Question 24Clinical Pathology: Blood Banking/Transfusion Medicine

A pregnant woman is alloimmunized to the Kell antigen. Which test is the standard method for monitoring fetal anemia?

  1. Amniotic fluid bilirubin (ΔOD450)
  2. Fetal umbilical artery Doppler
  3. Maternal antibody titer every 2 weeks
  4. Middle cerebral artery peak systolic velocity Correct answer.

Explanation

Fetal middle cerebral artery peak systolic velocity is the standard noninvasive test for detecting fetal anemia, including in Kell alloimmunization. Kell antibodies impair erythropoiesis, so amniotic fluid bilirubin is less reliable in this setting.

Question 25Clinical Pathology: Blood Banking/Transfusion Medicine

A 60-year-old woman with no prior history of thrombocytopenia develops severe thrombocytopenia and bleeding 8 days after a red cell transfusion. What is the most likely diagnosis?

  1. Thrombotic thrombocytopenic purpura
  2. Posttransfusion purpura Correct answer.
  3. Disseminated intravascular coagulation
  4. Heparin-induced thrombocytopenia

Explanation

Posttransfusion purpura occurs 5 to 12 days after transfusion and is caused by antibodies such as anti-HPA-1a that destroy both donor and the patient's own platelets. Treatment is intravenous immune globulin, and subsequent transfusions require antigen-negative components.

Question 26Clinical Pathology: Blood Banking/Transfusion Medicine

Platelet concentrates are stored under which conditions to maintain post-transfusion viability?

  1. 1–6°C with continuous agitation
  2. 37°C with continuous agitation
  3. 20–24°C without agitation
  4. 20–24°C with continuous agitation Correct answer.

Explanation

Platelets are stored at 20–24°C with continuous gentle agitation to maintain pH and oxygen delivery; cold storage causes platelet activation and rapid clearance. Continuous agitation helps preserve viability for the usual 5- to 7-day shelf life.

Question 27Clinical Pathology: Blood Banking/Transfusion Medicine

Which component is the main therapeutic reason for administering cryoprecipitate?

  1. Fibrinogen replacement Correct answer.
  2. Protein C replacement
  3. Factor IX replacement
  4. Platelet count increment

Explanation

Cryoprecipitate is rich in fibrinogen, factor VIII, von Willebrand factor, and factor XIII, but its most common current indication is fibrinogen replacement in hypofibrinogenemia or massive hemorrhage. It is not a source of all coagulation factors or platelets.

Question 28Clinical Pathology: Blood Banking/Transfusion Medicine

Which transfusion-transmitted infection is currently the most common cause of infectious transfusion-related death in the United States?

  1. Bacterial contamination of platelets Correct answer.
  2. West Nile virus infection
  3. Human immunodeficiency virus infection
  4. Hepatitis B virus infection

Explanation

Bacterial contamination, especially of room-temperature-stored platelet units, is the leading cause of transfusion-transmitted infectious death in the United States. Donor screening and nucleic acid testing have greatly reduced viral transmission.

Question 29Clinical Pathology: Blood Banking/Transfusion Medicine

Which mechanism best explains a febrile nonhemolytic transfusion reaction?

  1. Bacterial endotoxin in the transfused unit
  2. Complement-mediated intravascular hemolysis
  3. Cytokines accumulated during component storage Correct answer.
  4. Donor red cell hemolysis before transfusion

Explanation

Febrile nonhemolytic reactions are caused by cytokines and leukocyte-derived mediators that accumulate during storage, and sometimes by recipient antibodies against donor leukocytes. They are usually mild and diagnosed after hemolysis and sepsis are excluded.

Question 30Clinical Pathology: Blood Banking/Transfusion Medicine

Red cell concentrates are stored at which temperature range?

  1. 37°C
  2. −18°C or colder
  3. 1–6°C Correct answer.
  4. 20–24°C

Explanation

Red cells are stored at 1–6°C in a preservative solution to slow metabolism and limit bacterial growth. Frozen storage at −18°C or colder is used only for special components such as rare donor units.

Question 31Clinical Pathology: Blood Banking/Transfusion Medicine

Which measure most effectively reduces the risk of transfusion-transmitted cytomegalovirus for an at-risk seronegative recipient?

  1. Washing of red cell units
  2. Use of fresh-frozen plasma instead of red cells
  3. Leukoreduction of cellular components Correct answer.
  4. Irradiation of cellular components

Explanation

Cytomegalovirus is carried within leukocytes, so leukoreduction or use of CMV-seronegative units prevents transmission. Irradiation prevents transfusion-associated graft-versus-host disease but does not eliminate the virus.

Question 32Clinical Pathology: Blood Banking/Transfusion Medicine

A patient develops fever, flank pain, hypotension, and red urine minutes after a red cell transfusion begins. Which is the most likely cause?

  1. Circulatory overload from too rapid infusion
  2. Mild allergic reaction with urticaria
  3. ABO-incompatible unit from a clerical error Correct answer.
  4. Febrile nonhemolytic transfusion reaction

Explanation

The abrupt onset of fever, pain, hypotension, and hemoglobinuria during transfusion indicates acute intravascular hemolysis, most often from ABO incompatibility due to misidentification. The transfusion must be stopped immediately and the reaction evaluated.

Question 33Clinical Pathology: Blood Banking/Transfusion Medicine

A patient transfused 7 days ago now has falling hemoglobin, jaundice, and a positive direct antiglobulin test. Which antibody is a common cause?

  1. Anti-K Correct answer.
  2. Anti-A
  3. Anti-H
  4. Anti-I

Explanation

Delayed hemolytic transfusion reactions result from an anamnestic alloantibody response, commonly to Kell, Rh, or Kidd antigens, and often occur 5–10 days after transfusion. The antibody screen may be negative before transfusion because the antibody titer has fallen.

Question 34Clinical Pathology: Blood Banking/Transfusion Medicine

A patient develops urticaria and pruritus without fever or hypotension during a red cell transfusion. Which is the most appropriate initial management?

  1. Continue the transfusion at the same rate and observe
  2. Give intramuscular epinephrine immediately
  3. Permanently defer all future transfusions
  4. Stop, give antihistamine, restart if resolved Correct answer.

Explanation

Isolated urticaria and pruritus indicate a mild allergic reaction; the transfusion is paused, an antihistamine is given, and the same unit may be restarted once symptoms resolve. Epinephrine is reserved for anaphylaxis with airway or hemodynamic compromise.

Question 35Clinical Pathology: Blood Banking/Transfusion Medicine

Which medication class is associated with hypotensive transfusion reactions?

  1. Beta blockers
  2. Loop diuretics
  3. Proton pump inhibitors
  4. ACE inhibitors Correct answer.

Explanation

Hypotensive transfusion reactions occur within minutes of starting transfusion and are associated with ACE inhibitor use, which impairs bradykinin degradation. The transfusion is stopped and supportive care is given.

Question 36Clinical Pathology: Blood Banking/Transfusion Medicine

Which plasma component can be transfused to a patient of any ABO group without regard to the recipient's ABO type?

  1. Group B plasma
  2. Group AB plasma Correct answer.
  3. Group O plasma
  4. Group A plasma

Explanation

Group AB plasma lacks anti-A and anti-B antibodies, so it is compatible with all ABO red cell types. Group O plasma contains both antibodies and is not universally compatible.

Question 37Clinical Pathology: Blood Banking/Transfusion Medicine

For which indication is washing of red cell units most appropriate?

  1. Prevention of transfusion-associated graft-versus-host disease
  2. Prevention of febrile nonhemolytic reactions
  3. Prevention of cytomegalovirus transmission
  4. Prevention of severe recurrent allergic transfusion reactions Correct answer.

Explanation

Washing removes residual plasma proteins and is used for patients with severe recurrent allergic reactions or IgA deficiency with anti-IgA. Leukoreduction prevents febrile reactions and CMV transmission, while irradiation prevents graft-versus-host disease.

Question 38Clinical Pathology: Blood Banking/Transfusion Medicine

Which test is used to quantify fetomaternal hemorrhage and guide Rh immune globulin dosing?

  1. Direct antiglobulin test
  2. Kleihauer-Betke test Correct answer.
  3. Rosette test alone
  4. Amniotic fluid bilirubin measurement

Explanation

The Kleihauer-Betke acid elution test identifies and quantifies fetal red cells in maternal blood, allowing calculation of the RhIG dose after a large hemorrhage. The rosette test is a screening method and is not quantitative.

Question 39Clinical Pathology: Blood Banking/Transfusion Medicine

What is the maximum storage period for a red cell unit collected in an additive solution and stored at 1–6°C?

  1. 21 days
  2. 60 days
  3. 42 days Correct answer.
  4. 35 days

Explanation

Red cells in an additive solution can be stored for up to 42 days at 1–6°C, provided the unit meets ongoing quality requirements. The allowed period is shorter for some special preparations, such as washed or frozen-deglycerolized units.

Question 40Clinical Pathology: Blood Banking/Transfusion Medicine

Treatment of reagent red cells with ficin or papain most likely destroys which antigen?

  1. Kell (K)
  2. Kidd (Jka)
  3. Duffy (Fya) Correct answer.
  4. RhD

Explanation

Proteolytic enzymes destroy Duffy and MNS antigens but enhance Rh, Kidd, and Lewis reactivity; Kell antigens are generally enzyme resistant. This pattern helps identify antibodies in panel testing.

Question 41Clinical Pathology: Blood Banking/Transfusion Medicine

A patient's serum agglutinates all ABO reagent cells, the forward type is group O, and the serum contains anti-H. Which phenotype is most likely?

  1. Bombay (Oh) Correct answer.
  2. A2 subgroup
  3. Acquired B
  4. Weak D

Explanation

Bombay phenotype individuals lack H antigen and therefore cannot express A or B antigens; their serum contains anti-H along with anti-A and anti-B. They must receive only Oh red cells.

Question 42Clinical Pathology: Blood Banking/Transfusion Medicine

Which transfusion strategy is preferred for secondary stroke prevention in a child with sickle cell disease and iron overload?

  1. Erythrocytapheresis to lower HbS Correct answer.
  2. Plasma exchange
  3. Simple transfusion to a hemoglobin level of 14 g/dL
  4. Platelet transfusion

Explanation

Erythrocytapheresis removes sickle cells and replaces them with donor red cells, lowering HbS without adding as much iron as repeated simple transfusions. Simple transfusion can also cause hyperviscosity when hemoglobin is raised too high.

Question 43Clinical Pathology: Blood Banking/Transfusion Medicine

Which situation most clearly warrants use of a blood warmer?

  1. Routine outpatient transfusion of one unit
  2. Rapid massive transfusion of cold red cells Correct answer.
  3. Transfusion of platelets through a standard filter
  4. Transfusion of fresh frozen plasma over 4 hours

Explanation

Blood warming is indicated for rapid massive transfusion, exchange transfusion, and patients with cold agglutinin disease to prevent hypothermia and cardiac arrhythmia. Routine slow transfusion at normal flow rates does not require warming.

Question 44Clinical Pathology: Blood Banking/Transfusion Medicine

A patient with warm autoimmune hemolytic anemia has a positive DAT and panreactive serum. Which technique is most useful to detect an underlying alloantibody?

  1. Autoadsorption using the patient's own red cells
  2. Direct antiglobulin testing of donor cells
  3. Alloadsorption with phenotyped donor red cells Correct answer.
  4. Saline replacement

Explanation

In warm autoimmune hemolytic anemia, the autoantibody can mask an underlying alloantibody; alloadsorption with phenotyped donor cells removes the autoantibody while leaving alloantibodies in the serum. Autoadsorption is preferred only when the patient has not been recently transfused.

Question 45Clinical Pathology: Blood Banking/Transfusion Medicine

Which statement best describes the effect of nucleic acid testing on transfusion-transmitted hepatitis C?

  1. It eliminates the need for donor questionnaires
  2. It is less sensitive than antibody testing in early infection
  3. It shortens the window period versus serology alone Correct answer.
  4. It detects only past resolved infection

Explanation

Nucleic acid testing detects viral RNA earlier than antibody assays, shortening the window period and reducing residual transfusion-transmitted hepatitis C. Donor screening questionnaires and serologic testing remain part of the overall safety process.

Question 46Clinical Pathology: Blood Banking/Transfusion Medicine

A neonate has severe thrombocytopenia and intracranial hemorrhage at birth, while the mother's platelet count is normal. Which is the most likely diagnosis?

  1. Disseminated intravascular coagulation
  2. Neonatal alloimmune thrombocytopenia Correct answer.
  3. Maternal immune thrombocytopenia
  4. Hereditary macrothrombocytopenia

Explanation

Neonatal alloimmune thrombocytopenia results from maternal alloantibodies against fetal platelet antigens, most commonly HPA-1a, and the mother's platelet count is typically normal. It can cause severe intracranial hemorrhage in the first affected pregnancy.

Question 47Clinical Pathology: Chemical Pathology and Immunopathology/Serology

Which condition most commonly produces a spuriously elevated serum potassium result?

  1. Diabetic ketoacidosis
  2. Marked thrombocytosis Correct answer.
  3. Primary adrenal insufficiency
  4. Acute kidney injury

Explanation

Serum potassium rises falsely when potassium leaks from cells after the blood clots in the tube; marked thrombocytosis or leukocytosis, in vitro hemolysis, and prolonged fist clenching are classic settings. Because plasma is separated from cells before analysis, a paired plasma potassium is usually normal.

Question 48Clinical Pathology: Chemical Pathology and Immunopathology/Serology

A serum sample has sodium 138 mmol/L, glucose 180 mg/dL, and urea nitrogen 28 mg/dL. What is the calculated serum osmolality in mOsm/kg?

  1. 316
  2. 296 Correct answer.
  3. 276
  4. 306

Explanation

Calculated osmolality equals 2 x sodium plus glucose divided by 18 plus urea nitrogen divided by 2.8, giving 276 + 10 + 10 = 296 mOsm/kg. The measured osmolality minus this value is the osmolal gap.

Question 49Clinical Pathology: Chemical Pathology and Immunopathology/Serology

Which analyte is the most specific marker of myocardial injury?

  1. Cardiac troponin I Correct answer.
  2. Creatine kinase MB isoenzyme
  3. Myoglobin
  4. Lactate dehydrogenase isoenzyme

Explanation

Cardiac troponin I and T are expressed only in myocardium, so elevation indicates cardiac injury with high specificity. CK-MB is also present in skeletal muscle, myoglobin rises early but lacks specificity, and lactate dehydrogenase is obsolete for this purpose.

Question 50Clinical Pathology: Chemical Pathology and Immunopathology/Serology

Which autoantibody is most specific for systemic lupus erythematosus?

  1. Anti-histone
  2. Anti-double-stranded DNA Correct answer.
  3. Anti-U1 ribonucleoprotein
  4. Anti-Ro/SSA

Explanation

Antibodies to double-stranded DNA are highly specific for systemic lupus erythematosus and titers correlate with renal flares. Anti-histone antibodies suggest drug-induced lupus, anti-Ro/SSA is typical of Sjogren syndrome, and anti-U1 ribonucleoprotein marks mixed connective tissue disease.