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ASCP C practice questions

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Question 1Blood Banking / Immunohematology

Why is reverse ABO grouping not performed on a blood sample from a 2-month-old infant?

  1. Infants have ABO antibodies of maternal origin only.
  2. Infants lack ABO antigens on their red cells.
  3. Infants have not yet produced ABO antibodies. Correct answer.
  4. Infants' red cells are coated with complement.

Explanation

ABO antibodies are IgM and develop after birth, usually becoming detectable by about 4 to 6 months of age. Therefore, reverse grouping is unreliable in young infants and only forward typing is used.

Question 2Blood Banking / Immunohematology

A donor unit is D-negative by immediate spin but positive by the weak D test. How should the unit be labeled?

  1. D-positive, because weak D expresses D antigen Correct answer.
  2. D-negative unless the recipient is D-negative
  3. Unsuitable for transfusion to any recipient
  4. D-negative, because weak D is not clinically significant

Explanation

Donor units that are weak D positive are labeled D-positive because the red cells express D antigen and can immunize a D-negative recipient. Weak D testing is not routinely required for transfusion recipients.

Question 3Blood Banking / Immunohematology

Polyspecific antihuman globulin used in antibody screening contains antibodies directed against which two substances?

  1. IgM and IgA
  2. IgG and C3d Correct answer.
  3. Albumin and fibrinogen
  4. C3b and C4d

Explanation

Polyspecific AHG contains anti-IgG and anti-C3d, allowing detection of red cell-bound IgG and complement. This is why it is used in the indirect and direct antiglobulin tests.

Question 4Blood Banking / Immunohematology

Which blood component is stored at 20-24°C with continuous agitation?

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

Explanation

Platelet concentrates are stored at 20-24°C with continuous agitation to maintain platelet viability and allow gas exchange. Red cells, plasma, and cryoprecipitate are stored under different conditions.

Question 5Blood Banking / Immunohematology

The immediate spin crossmatch primarily detects incompatibility involving which blood group system?

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

Explanation

The immediate spin crossmatch detects IgM antibodies that agglutinate at room temperature, most importantly anti-A and anti-B. It confirms ABO compatibility between donor and recipient.

Question 6Blood Banking / Immunohematology

Which immunoglobulin class makes up most ABO antibodies?

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

Explanation

ABO antibodies are predominantly IgM, which explains their ability to agglutinate red cells at room temperature and in immediate spin testing. They are naturally occurring antibodies directed against absent ABO antigens.

Question 7Blood Banking / Immunohematology

A direct antiglobulin test detects antibodies or complement attached to which target?

  1. Antibodies in patient serum
  2. Reagent RBCs in vitro
  3. Donor RBCs in the unit
  4. Patient RBCs in vivo Correct answer.

Explanation

The DAT detects IgG or complement already bound to the patient's circulating red cells in vivo. An indirect antiglobulin test, by contrast, detects antibodies in serum that bind reagent red cells in vitro.

Question 8Blood Banking / Immunohematology

Which blood components should be irradiated to prevent transfusion-associated graft-versus-host disease?

  1. Platelet-poor plasma
  2. Cryoprecipitate
  3. Cellular components Correct answer.
  4. Fresh frozen plasma

Explanation

Irradiation prevents donor T lymphocytes from proliferating and causing transfusion-associated graft-versus-host disease. Cellular components, such as red cells and platelets, contain viable lymphocytes and are the components that require irradiation for at-risk patients.

Question 9Blood Banking / Immunohematology

An antibody reacts more strongly with ficin-treated reagent red cells than with untreated cells. Which antibody is most likely?

  1. Anti-S
  2. Anti-D Correct answer.
  3. Anti-Fya
  4. Anti-M

Explanation

Proteolytic enzymes such as ficin enhance many Rh antibodies by increasing antigen accessibility. In contrast, enzyme treatment destroys Duffy and MNS antigens, reducing reactivity of antibodies such as anti-Fya, anti-M, and anti-S.

Question 10Blood Banking / Immunohematology

What is the usual immunoglobulin class and clinical significance of anti-Lea?

  1. IgM, causes delayed hemolytic reaction
  2. IgA, causes TRALI
  3. IgG, causes HDFN
  4. IgM, not clinically significant Correct answer.

Explanation

Anti-Lea is typically IgM, binds complement, and is usually not clinically significant for transfusion or pregnancy. Lewis antigens are not well developed on fetal red cells, so anti-Lea rarely causes hemolytic disease of the fetus and newborn.

Question 11Blood Banking / Immunohematology

The Fy(a-b-) phenotype is associated with resistance to which infection?

  1. Babesia microti
  2. Plasmodium vivax Correct answer.
  3. Toxoplasma gondii
  4. Plasmodium falciparum

Explanation

Duffy antigens serve as receptors for Plasmodium vivax on red cells. Individuals with the Fy(a-b-) phenotype lack these receptors and are resistant to P. vivax infection.

Question 12Blood Banking / Immunohematology

Which antibody is a well-recognized cause of severe hemolytic disease of the fetus and newborn?

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

Explanation

Anti-K is an IgG antibody that can cause severe HDFN, sometimes with relatively low bilirubin levels because Kell antibodies suppress fetal erythropoiesis. Kell antigens are present on fetal red cells early in gestation.

Question 13Blood Banking / Immunohematology

Anti-I reacts most strongly at which temperature?

  1. 4°C Correct answer.
  2. 22°C
  3. 56°C
  4. 37°C

Explanation

Anti-I is a cold-reacting IgM antibody that shows optimal reactivity at 4°C. It is associated with cold agglutinin disease and can cause cold autoagglutination.

Question 14Blood Banking / Immunohematology

A patient develops fever and chills 1 hour after an RBC transfusion, with no evidence of hemolysis. Which reaction is most likely?

  1. TRALI
  2. Acute hemolytic reaction
  3. Bacterial contamination
  4. Febrile nonhemolytic Correct answer.

Explanation

Febrile nonhemolytic transfusion reactions are characterized by fever and chills without hemolysis and are often caused by cytokines or leukocyte-derived substances in the component. Leukoreduction reduces the frequency of these reactions.

Question 15Blood Banking / Immunohematology

TRALI is most often associated with donor antibodies directed against which target?

  1. Anti-HLA Correct answer.
  2. Anti-Lewis
  3. Anti-Kidd
  4. Anti-Duffy

Explanation

TRALI is commonly associated with donor antibodies against HLA class I or II antigens or against neutrophil antigens. These antibodies activate recipient neutrophils and damage the pulmonary endothelium.

Question 16Blood Banking / Immunohematology

Which patient group requires irradiated cellular blood components?

  1. Patients with ABO mismatch only
  2. Patients with von Willebrand disease
  3. Stem cell transplant recipients Correct answer.
  4. Patients with iron deficiency

Explanation

Patients receiving hematopoietic stem cell transplants are at risk for transfusion-associated graft-versus-host disease and require irradiated cellular components. Irradiation prevents donor T lymphocytes from engrafting and proliferating.

Question 17Blood Banking / Immunohematology

Which requirement must be met before a computer crossmatch can be used?

  1. A positive antibody screen with a known antibody
  2. No historical ABO type available in the record
  3. Two concordant ABO types and negative screen Correct answer.
  4. A positive direct antiglobulin test result

Explanation

A computer crossmatch requires at least two concordant ABO typings, a negative antibody screen, and no history of clinically significant antibodies. It also requires validated computer software and a secure database.

Question 18Blood Banking / Immunohematology

What is the minimum patient identification required on a pretransfusion blood specimen label?

  1. Date of birth only
  2. Name and medical record number Correct answer.
  3. Blood type and antibody screen result
  4. Room number and diagnosis

Explanation

Pretransfusion specimens must be labeled with two independent patient identifiers, such as full name and unique medical record number. The label must be attached at the bedside when the specimen is collected.

Question 19Blood Banking / Immunohematology

Under standard blood bank conditions, platelets can be stored for how long?

  1. 5 days Correct answer.
  2. 3 days
  3. 24 hours
  4. 35 days

Explanation

Platelets are stored at 20-24°C with continuous agitation and generally have a shelf life of 5 days. This short storage period reflects the risk of bacterial proliferation and loss of platelet function.

Question 20Blood Banking / Immunohematology

Once thawed and stored at 1-6°C, fresh frozen plasma should be transfused within what time period?

  1. 4 hours
  2. 12 hours
  3. 6 hours
  4. 24 hours Correct answer.

Explanation

Thawed fresh frozen plasma can be stored at 1-6°C and should be transfused within 24 hours. If not used within that time, it must be discarded or managed according to local policies for previously thawed plasma.

Question 21Blood Banking / Immunohematology

A patient's red cells agglutinate with anti-A but not with anti-A1, and the serum contains anti-A1. Which ABO subgroup is most likely?

  1. A3
  2. Ax
  3. A1
  4. A2 Correct answer.

Explanation

A2 red cells lack the A1 antigen, so they do not react with anti-A1, and some A2 individuals produce anti-A1 in their serum. A1 cells would react with anti-A1, which rules out the A1 subgroup.

Question 22Blood Banking / Immunohematology

A patient with a partial D phenotype receives D-positive red cells. What is the main transfusion risk?

  1. TRALI
  2. Posttransfusion purpura
  3. Immediate ABO hemolysis
  4. Anti-D alloimmunization Correct answer.

Explanation

Partial D red cells lack some D epitopes, so exposure to a full D-positive red cell unit can stimulate anti-D production. For this reason, patients with partial D may be managed as D-negative for transfusion.

Question 23Blood Banking / Immunohematology

In Rh hemolytic disease of the fetus and newborn, which anti-D titer is generally considered the threshold for further evaluation?

  1. 1:8
  2. 1:2
  3. 1:256
  4. 1:16 Correct answer.

Explanation

An anti-D titer of 1:16 or greater by indirect antiglobulin testing is generally considered the threshold for additional evaluation, such as amniotic fluid analysis or middle cerebral artery Doppler studies. Titers below this level are usually monitored serially.

Question 24Blood Banking / Immunohematology

Posttransfusion purpura is most commonly associated with which antibody?

  1. Anti-K
  2. Anti-HPA-1a Correct answer.
  3. Anti-A
  4. Anti-HLA class I

Explanation

Posttransfusion purpura is most often caused by anti-HPA-1a in a previously sensitized patient, typically a woman with a history of pregnancy. The platelet count falls markedly about 5 to 10 days after transfusion.

Question 25Blood Banking / Immunohematology

Which technique is commonly used to elute IgG antibodies from red cells in warm autoimmune hemolytic anemia?

  1. Chloroquine elution
  2. Heat elution at 56°C
  3. Acid elution Correct answer.
  4. Polyethylene glycol

Explanation

Acid elution, such as with glycine-HCl, disrupts the binding between IgG and red cell antigens and is commonly used for warm autoantibodies. Heat elution is more often used for cold-reacting IgM antibodies.

Question 26Blood Banking / Immunohematology

A D-negative woman delivers a D-positive infant. A Kleihauer-Betke stain shows 1.5% fetal red cells in her circulation, and she has already received the routine postpartum 300 µg dose of Rh immune globulin. Using an estimated maternal blood volume of 5000 mL and assuming that one 300 µg vial neutralizes 30 mL of fetal whole blood, how many additional 300 µg vials are required?

  1. 2 Correct answer.
  2. 1
  3. 3
  4. 4

Explanation

The volume of the fetal bleed is estimated by multiplying the percentage of fetal cells by the maternal blood volume (0.015 × 5000 mL = 75 mL of fetal whole blood). Dividing 75 mL by the 30 mL covered by each vial gives 2.5 vials, which must be rounded up to 3 vials total. Because the routine 300 µg dose has already been given, 2 additional vials are needed.

Question 27Clinical Chemistry

A solution measured in a spectrophotometer with a 1.0-cm light path gives an absorbance of 0.300. If the same solution is remeasured in a cuvette with a 2.0-cm path length, what absorbance is expected?

  1. 0.150
  2. 1.200
  3. 0.300
  4. 0.600 Correct answer.

Explanation

According to the Beer-Lambert law, absorbance is directly proportional to path length as well as to concentration. Doubling the path length while keeping concentration constant doubles the absorbance, from 0.300 to 0.600.

Question 28Clinical Chemistry

A fasting plasma glucose concentration at or above which value, confirmed by repeat testing, is diagnostic of diabetes mellitus?

  1. 126 mg/dL (7.0 mmol/L) Correct answer.
  2. 200 mg/dL (11.1 mmol/L)
  3. 140 mg/dL (7.8 mmol/L)
  4. 100 mg/dL (5.6 mmol/L)

Explanation

A fasting plasma glucose of 126 mg/dL (7.0 mmol/L) or higher on two occasions meets the diagnostic criterion for diabetes mellitus. Values from 100 to 125 mg/dL define impaired fasting glucose rather than diabetes.

Question 29Clinical Chemistry

Under Westgard multirule quality control, which rule is violated when a single control measurement falls more than 3 SD from the mean?

  1. 2-2s
  2. R-4s
  3. 4-1s
  4. 1-3s Correct answer.

Explanation

The 1-3s rule is triggered by one control value exceeding the mean by more than 3 SD, and it is generally treated as a rejection rule indicating random error. The other multirules require patterns across two or more consecutive control values.

Question 30Clinical Chemistry

The serum anion gap is calculated with which expression?

  1. Cl + HCO3 − Na
  2. (Na + HCO3) − Cl
  3. Na − (Cl + HCO3) Correct answer.
  4. Na + Cl − HCO3

Explanation

The anion gap estimates unmeasured anions by subtracting the measured anions chloride and bicarbonate from the major measured cation sodium. Results are reported in mmol/L and a typical reference range is roughly 8 to 16 mmol/L.

Question 31Clinical Chemistry

Serum creatinine is produced mainly by which process?

  1. Hepatic deamination of amino acids
  2. Hepatic conjugation of bilirubin
  3. Nonenzymatic dehydration of muscle creatine phosphate Correct answer.
  4. Catabolism of dietary purines

Explanation

Creatine phosphate in skeletal muscle spontaneously and nonenzymatically loses water and phosphate to form creatinine, which is released into plasma at a relatively constant rate. This constant generation is why creatinine is useful for estimating glomerular filtration.

Question 32Clinical Chemistry

Glycated hemoglobin (HbA1c) reflects the average blood glucose over approximately what time period?

  1. The preceding 2 to 3 months Correct answer.
  2. The preceding 7 days
  3. The preceding 24 hours
  4. The preceding 12 months

Explanation

Glycation accumulates over the lifespan of the erythrocyte, which averages about 120 days, so HbA1c reflects mean glycemia over roughly the preceding 2 to 3 months. Shorter-term markers such as glycated albumin reflect only a few weeks.

Question 33Clinical Chemistry

Unconjugated bilirubin is transported in plasma primarily bound to which protein?

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

Explanation

Unconjugated bilirubin is water insoluble and circulates tightly but reversibly bound to albumin, which carries it to the liver for conjugation. Displacement from albumin by drugs or low albumin can raise the free fraction and increase kernicterus risk in neonates.

Question 34Clinical Chemistry

Which biomarker is most specific for myocardial injury?

  1. Aspartate aminotransferase
  2. Cardiac troponin I Correct answer.
  3. Creatine kinase MB
  4. Myoglobin

Explanation

Cardiac troponin I and T are expressed only in myocardium and are therefore the most specific markers of myocardial necrosis. CK-MB, myoglobin, and AST also occur in skeletal muscle or other tissues and are less specific.

Question 35Clinical Chemistry

A blood specimen with markedly increased lipid content is analyzed for sodium by an indirect ion-selective electrode method that requires dilution. The reported sodium is most likely to be:

  1. Falsely decreased Correct answer.
  2. Falsely decreased only if the specimen is also hemolyzed
  3. Falsely increased
  4. Unaffected, because ion-selective electrodes do not respond to lipids

Explanation

Indirect ion-selective electrodes measure sodium in a diluted aliquot, and the volume displaced by excess lipid is not accounted for, so results are falsely low, a phenomenon called pseudohyponatremia. Direct ion-selective electrodes measure undiluted whole blood or plasma and are not affected by the lipid phase.

Question 36Clinical Chemistry

In vitro hemolysis in a serum specimen is most likely to produce which pattern of results?

  1. Falsely low bilirubin with high albumin
  2. Falsely low potassium with high sodium
  3. Falsely high potassium, lactate dehydrogenase, and AST Correct answer.
  4. Falsely high glucose with low phosphate

Explanation

Erythrocytes contain high concentrations of potassium, lactate dehydrogenase, and AST, so lysis releases these analytes into the serum and falsely elevates them. Hemolysis also interferes spectrophotometrically and dilutes the plasma with red cell contents.

Question 37Clinical Chemistry

A patient has an isolated elevation of serum alkaline phosphatase. Which additional test best helps distinguish a hepatic from a skeletal source?

  1. Gamma-glutamyl transferase Correct answer.
  2. Creatine kinase
  3. Amylase
  4. Lactate dehydrogenase

Explanation

Gamma-glutamyl transferase is elevated in hepatobiliary disease but not in bone disease, so an elevated GGT alongside alkaline phosphatase supports a hepatic origin. A normal GGT in that setting points toward bone as the source.

Question 38Clinical Chemistry

Which expression correctly represents creatinine clearance calculated from a timed urine collection, where U is urine creatinine, P is plasma creatinine, and V is urine flow rate in mL/min?

  1. Ccr = (P × V) / U
  2. Ccr = (V × P) / U
  3. Ccr = (U × P) / V
  4. Ccr = (U × V) / P Correct answer.

Explanation

Clearance equals the amount excreted per unit time divided by the plasma concentration, giving Ccr = (U × V)/P. The result is conventionally expressed in mL/min and must be corrected for body surface area when compared with reference values.

Question 39Clinical Chemistry

With sodium, glucose, and blood urea nitrogen reported in mg/dL, calculated serum osmolality in mOsm/kg is best estimated by which formula?

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

Explanation

Sodium contributes its accompanying anions, so it is multiplied by two, while glucose and urea are converted from mg/dL to mmol/L by dividing by their molecular weights, 18 and 2.8 respectively. A measured osmolality exceeding the calculated value by a large margin suggests an unmeasured osmole such as ethanol or methanol.

Question 40Clinical Chemistry

Arterial blood gas results are pH 7.28, pCO2 58 mmHg, and HCO3 26 mmol/L. Which interpretation best fits these results?

  1. Respiratory alkalosis
  2. Metabolic alkalosis
  3. Metabolic acidosis with respiratory compensation
  4. Respiratory acidosis Correct answer.

Explanation

The pH is acidemic and the pCO2 is markedly elevated, identifying a primary respiratory acidosis. A near-normal bicarbonate suggests the process is acute or only minimally compensated, since renal compensation requires days to develop.

Question 41Clinical Chemistry

A patient has a total calcium of 8.0 mg/dL and an albumin of 2.0 g/dL. Using the rule that total calcium changes by 0.8 mg/dL for each 1.0 g/dL that albumin differs from 4.0 g/dL, the albumin-corrected calcium is:

  1. 8.0 mg/dL
  2. 10.4 mg/dL
  3. 8.8 mg/dL
  4. 9.6 mg/dL Correct answer.

Explanation

The albumin deficit is 2.0 g/dL, so 2.0 × 0.8 = 1.6 mg/dL is added to the measured total calcium, giving 9.6 mg/dL. Correcting for albumin prevents under-recognition of normocalcemia in hypoalbuminemic patients.

Question 42Clinical Chemistry

In a competitive immunoassay using labeled antigen, increasing the concentration of analyte in the patient sample produces which change?

  1. No change in the amount of bound label
  2. An increase in bound labeled antigen
  3. A proportional increase in enzyme activity
  4. A decrease in bound labeled antigen Correct answer.

Explanation

In a competitive format, patient analyte and labeled antigen compete for a limited number of antibody sites, so more analyte means less labeled antigen bound. Competitive assays therefore show an inverse relationship between analyte concentration and signal.

Question 43Clinical Chemistry

For therapeutic drug monitoring of an orally administered drug at steady state, a trough specimen should be collected:

  1. Two hours after a dose
  2. At any random time in the dosing interval
  3. Thirty minutes after a dose
  4. Immediately before the next dose Correct answer.

Explanation

The trough is the lowest concentration in the dosing interval and is drawn just before the next dose, after distribution is complete. Consistent timing relative to dosing is essential for interpreting results against therapeutic ranges.

Question 44Clinical Chemistry

The most widely used enzymatic method for measuring serum uric acid is based on which reaction?

  1. Oxidation of glucose by glucose oxidase
  2. Oxidation of uric acid by uricase to allantoin and hydrogen peroxide Correct answer.
  3. Hydrolysis of urea by urease
  4. Reduction of alkaline picrate

Explanation

Uricase oxidizes uric acid to allantoin and hydrogen peroxide, and the peroxide is then measured in a coupled peroxidase reaction. The decrease in absorbance at about 293 nm can also be monitored directly.

Question 45Clinical Chemistry

Serum protein electrophoresis shows a dense, narrow band in the gamma region. This finding is most consistent with:

  1. A monoclonal gammopathy Correct answer.
  2. Alpha-1 antitrypsin deficiency
  3. Iron deficiency anemia
  4. Nephrotic syndrome

Explanation

A restricted, narrow gamma band represents a monoclonal immunoglobulin produced by a single plasma cell clone, as seen in multiple myeloma or monoclonal gammopathy of undetermined significance. Polyclonal increases instead produce a broad, diffuse gamma rise.

Question 46Clinical Chemistry

Which laboratory pattern is typical of primary hypothyroidism?

  1. Low TSH with low free T4
  2. High TSH with low free T4 Correct answer.
  3. High TSH with high free T4
  4. Low TSH with high free T4

Explanation

In primary hypothyroidism the thyroid gland fails to produce hormone, so free T4 is low and the pituitary responds with an elevated TSH. A low TSH with low free T4 instead suggests central (secondary) hypothyroidism.

Question 47Clinical Chemistry

A serum sample shows CK-MB activity that exceeds total creatine kinase activity, with no clinical evidence of myocardial infarction. The most likely explanation is:

  1. Skeletal muscle trauma
  2. Acute myocardial infarction
  3. Interference from hemolysis
  4. A macro-creatine kinase complex Correct answer.

Explanation

Macro-CK complexes are immunoglobulin-bound forms of creatine kinase that co-migrate with CK-MB in electrophoretic or immunoinhibition methods, producing a spuriously high CK-MB fraction. The discordance between CK-MB and total CK, in the absence of matching clinical findings, is the clue.

Question 48Clinical Chemistry

A delta check compares a patient's current result with previously reported results in order to:

  1. Determine the analytical sensitivity of an assay
  2. Establish a reference interval for the laboratory
  3. Verify the accuracy of the calibrators in use
  4. Detect possible specimen misidentification or mix-up Correct answer.

Explanation

A delta check flags unexpectedly large changes between consecutive results for the same patient, which most often signals a mislabeled or wrong specimen. It is a pre-reporting safeguard rather than a measure of calibration or assay performance.

Question 49Clinical Chemistry

A sweat chloride concentration of 60 mmol/L or greater, obtained by pilocarpine iontophoresis, supports which diagnosis in a child with suggestive clinical features?

  1. Cystic fibrosis Correct answer.
  2. Pancreatic insufficiency unrelated to cystic fibrosis
  3. Primary ciliary dyskinesia
  4. Bartter syndrome

Explanation

Pilocarpine iontophoresis stimulates sweating, and a chloride concentration of 60 mmol/L or more is diagnostic for cystic fibrosis; values from 30 to 59 mmol/L are intermediate. The test reflects defective chloride transport across epithelial membranes.

Question 50Clinical Chemistry

Which condition is most likely to produce a falsely low HbA1c relative to the patient's true average glucose?

  1. Prior splenectomy
  2. Hemolytic anemia with shortened red cell survival Correct answer.
  3. Vitamin B12 deficiency anemia
  4. Iron deficiency anemia

Explanation

HbA1c depends on glycation occurring over erythrocyte lifespan, so any state with accelerated red cell turnover shortens exposure time and lowers the result. Iron deficiency, B12 deficiency, and splenectomy instead tend to raise HbA1c by increasing red cell survival.