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ASCP BB practice questions

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Question 1Blood Group Systems and Immunohematology Theory

A patient's red cells type as group A by forward grouping. What should the reverse grouping demonstrate?

  1. Anti-A in the serum
  2. Anti-B in the serum Correct answer.
  3. Both anti-A and anti-B in the serum
  4. Neither anti-A nor anti-B in the serum

Explanation

Landsteiner's rule states that the serum contains antibodies directed against the ABH antigens absent from the red cells. Group A cells carry A antigen, so the serum should contain anti-B. Concordance between forward and reverse grouping confirms the ABO type.

Question 2Blood Group Systems and Immunohematology Theory

Which ABO group's plasma contains no anti-A or anti-B and can therefore be given to a recipient of any ABO group?

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

Explanation

Group AB individuals lack both anti-A and anti-B because their red cells express both antigens. Their plasma is thus compatible with all ABO types and serves as the universal plasma donor. Group O plasma, by contrast, contains both anti-A and anti-B.

Question 3Blood Group Systems and Immunohematology Theory

Which red cell phenotype confers resistance to invasion by Plasmodium vivax?

  1. Lu(a−b−)
  2. K0 (Kell null)
  3. Fy(a−b−) Correct answer.
  4. Jk(a−b−)

Explanation

The Duffy glycoprotein is the receptor used by P. vivax to enter reticulocytes. Individuals with the Fy(a−b−) phenotype, common in West African populations, lack this receptor and are resistant to vivax malaria.

Question 4Blood Group Systems and Immunohematology Theory

Which description best fits anti-I?

  1. IgG that reacts only in the antiglobulin phase
  2. IgM that reacts optimally near 4 °C Correct answer.
  3. IgM that reacts more strongly with cord cells than adult cells
  4. IgG that commonly causes severe HDFN

Explanation

Anti-I is a cold-reacting IgM autoantibody that binds adult red cells best at low temperatures and is the typical specificity in cold agglutinin disease. It reacts weakly with cord cells, which carry the i antigen rather than I.

Question 5Blood Group Systems and Immunohematology Theory

The indirect antiglobulin test is used to detect which of the following?

  1. IgG antibody in serum that binds reagent red cells in vitro Correct answer.
  2. IgM antibody reacting at immediate spin
  3. Complement components bound to the patient's red cells in vivo
  4. IgG coating the patient's red cells in vivo

Explanation

The indirect antiglobulin test incubates serum with reagent red cells so that antibody in the sample can bind in vitro; antihuman globulin then cross-links the cell-bound IgG. Detection of antibody already on the patient's own cells in vivo is the purpose of the direct antiglobulin test.

Question 6Blood Group Systems and Immunohematology Theory

Which reagent is used to distinguish A1 from A2 red cells?

  1. Anti-A,B reagent
  2. Ulex europaeus lectin
  3. Polyclonal anti-A reagent
  4. Dolichos biflorus lectin Correct answer.

Explanation

Dolichos biflorus lectin has anti-A1 specificity and agglutinates A1 cells while leaving A2 cells unagglutinated. This lectin is therefore used to confirm A1 status, for example when anti-A1 is suspected in an A2 individual.

Question 7Blood Group Systems and Immunohematology Theory

Which immunoglobulin class is a pentamer that directly agglutinates saline-suspended red cells at room temperature?

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

Explanation

IgM molecules are pentamers with ten antigen-binding sites, allowing them to bridge red cells and produce direct agglutination in saline without antihuman globulin. IgG is a monomer and generally requires the antiglobulin phase to be detected.

Question 8Blood Group Systems and Immunohematology Theory

Which antibody is the most common cause of severe hemolytic disease of the fetus and newborn?

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

Explanation

Anti-D is the classic IgG antibody responsible for severe HDFN because the D antigen is highly immunogenic and IgG1/IgG3 anti-D crosses the placenta. Prophylactic RhIG given to D-negative mothers has greatly reduced its incidence.

Question 9Blood Group Systems and Immunohematology Theory

A patient's red cells are nonreactive with anti-D at immediate spin. Which additional step is appropriate before reporting the patient as D-negative?

  1. Perform a weak D test with anti-D by IAT Correct answer.
  2. Test the patient's serum against D-positive reagent cells
  3. Repeat the test using only anti-C and anti-E reagents
  4. Perform a direct antiglobulin test on the patient's cells

Explanation

Weak D phenotypes express D at levels too low for immediate-spin detection, so a negative immediate-spin result is followed by incubation with anti-D and conversion to the antiglobulin phase. This weak D test prevents a weak D individual from being misclassified as D-negative and inappropriately given RhIG or D-negative blood.

Question 10Blood Group Systems and Immunohematology Theory

Which statement about anti-K is correct?

  1. It is usually IgG and reacts by IAT Correct answer.
  2. It reacts only with enzyme-treated red cells
  3. It is a naturally occurring IgM antibody reacting at room temperature
  4. It is directed against a low-incidence antigen

Explanation

Anti-K is an immune IgG antibody detected in the antiglobulin phase and is clinically significant for both transfusion and pregnancy. It is notable for causing HDFN through suppression of fetal erythropoiesis, so antibody titers correlate poorly with fetal disease severity.

Question 11Blood Group Systems and Immunohematology Theory

Anti-Jka is a classic cause of which adverse transfusion event?

  1. Febrile nonhemolytic reaction from cytokines
  2. Immediate intravascular hemolysis during the transfusion
  3. Delayed hemolytic transfusion reaction Correct answer.
  4. Anaphylaxis in IgA-deficient recipients

Explanation

Kidd antibodies often fall below detectable levels after sensitization, so a compatible crossmatch may be obtained, yet an anamnestic response causes red cell destruction days later. The resulting delayed hemolytic transfusion reaction typically appears as a falling hemoglobin with a newly positive antibody screen and DAT.

Question 12Blood Group Systems and Immunohematology Theory

Why can a person's Lewis phenotype change over time, for example during pregnancy?

  1. Lewis genes rearrange during erythroid maturation
  2. Lewis synthesis requires the RhD protein
  3. Lewis antigens are cleaved from the membrane by complement
  4. Lewis antigens are adsorbed from plasma lipoproteins Correct answer.

Explanation

Lewis antigens are not intrinsic membrane structures; they are glycolipids transferred from plasma onto the red cell surface. Because this adsorption depends on lipoprotein levels and the activity of the Lewis transferase, phenotypes can shift, and Lewis antigens may be lost from cells stored in vitro.

Question 13Blood Group Systems and Immunohematology Theory

Which feature best characterizes anti-M?

  1. It is directed against a high-incidence antigen of the MNS system
  2. It requires enzyme-treated cells to react
  3. It reacts only in the antiglobulin phase and often causes severe HDFN
  4. It is usually IgM and reacts best at room temperature Correct answer.

Explanation

Anti-M is typically a naturally occurring or immune IgM antibody that agglutinates saline-suspended M-positive cells optimally below 37 °C. It is usually of little clinical significance, although IgG examples have occasionally caused delayed hemolysis or mild HDFN.

Question 14Blood Group Systems and Immunohematology Theory

A tube indirect antiglobulin test is positive with polyspecific antihuman globulin. What is the appropriate next step?

  1. Titrate the serum against panel cells
  2. Test the cells with anti-IgG and anti-C3d separately Correct answer.
  3. Report the result as an IgG antibody
  4. Perform an elution from the patient's red cells to identify the antibody

Explanation

Polyspecific antihuman globulin contains both anti-IgG and anti-C3d, so a positive result does not identify what is coating the cells. Testing with the monospecific reagents separately shows whether IgG, complement, or both are present, which guides the interpretation and further workup.

Question 15Blood Group Systems and Immunohematology Theory

A serum reacts 2+ with Jk(a+b−) cells but only weakly with Jk(a+b+) cells. What does this pattern suggest?

  1. An autoantibody with apparent panreactivity
  2. An antibody to a high-incidence antigen
  3. A cold autoagglutinin of the Ii system
  4. Dosage, because homozygous cells express more antigen Correct answer.

Explanation

Antibodies showing dosage react more strongly with cells homozygous for the corresponding allele because those cells carry more antigen sites. Kidd antibodies are a classic example, reacting more weakly with heterozygous cells or appearing nonreactive when only heterozygous cells are tested.

Question 16Blood Group Systems and Immunohematology Theory

A group A2 patient's serum agglutinates A1 cells at room temperature but does not react with A2 cells or the patient's own cells. Which antibody is most likely present?

  1. Anti-A,B
  2. Anti-H
  3. Anti-I
  4. Anti-A1 Correct answer.

Explanation

Some A2 (and A2B) individuals produce an IgM anti-A1 that agglutinates A1 cells while sparing A2 and their own cells. It is usually not clinically significant, but it can cause ABO discrepancy in crossmatching and must be distinguished from a true ABO incompatibility.

Question 17Blood Group Systems and Immunohematology Theory

The presence of soluble A and B substances in saliva is controlled by which gene?

  1. ABO
  2. FUT1 (H)
  3. FUT3 (Le)
  4. FUT2 (Se) Correct answer.

Explanation

The Se gene, FUT2, encodes an alpha-2-fucosyltransferase that adds fucose to precursor chains in secretory tissues, producing soluble H, A, and B substances. Individuals who are homozygous for a nonfunctional FUT2 allele are nonsecretors and have no soluble ABH in secretions.

Question 18Blood Group Systems and Immunohematology Theory

A patient's direct antiglobulin test is 4+ with anti-IgG and negative with anti-C3d, and the eluate reacts with all panel cells. What does this indicate?

  1. A delayed reaction to Jka
  2. Drug-induced hemolysis from a cephalosporin
  3. Cold agglutinin syndrome
  4. Warm autoimmune hemolytic anemia Correct answer.

Explanation

Warm autoantibodies are IgG that coat red cells at body temperature, giving a DAT that is positive with anti-IgG and typically negative with anti-C3d. The eluate reacts with all cells because the autoantibody recognizes a ubiquitous antigen, often within the Rh system.

Question 19Blood Group Systems and Immunohematology Theory

One standard 300 µg dose of Rh immune globulin neutralizes approximately how much fetal whole blood?

  1. 300 mL
  2. 5 mL
  3. 125 mL
  4. 30 mL Correct answer.

Explanation

A 300 µg dose of RhIG neutralizes about 15 mL of fetal packed red cells, which corresponds to roughly 30 mL of fetal whole blood. Larger fetomaternal hemorrhages must be quantified, for example by Kleihauer-Betke staining or flow cytometry, and additional doses calculated.

Question 20Blood Group Systems and Immunohematology Theory

When a maternal anti-D titer reaches the critical level during pregnancy, which test best assesses whether the fetus is anemic?

  1. Kleihauer-Betke stain of maternal blood
  2. Middle cerebral artery peak systolic velocity by Doppler Correct answer.
  3. Repeat maternal antibody titer every week
  4. Maternal indirect bilirubin

Explanation

Once the anti-D titer reaches the critical level, Doppler measurement of middle cerebral artery peak systolic velocity is the noninvasive method of choice for detecting fetal anemia. Maternal titers indicate risk but do not reflect the degree of fetal anemia once disease is established.

Question 21Blood Group Systems and Immunohematology Theory

A patient's red cells are H-negative, and her serum reacts with all group O panel cells but not with her own cells. Which antibody is present?

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

Explanation

The Bombay (Oh) phenotype results from absent H antigen, so no A or B antigen can be built and the individual makes anti-H. Anti-H agglutinates all cells except other Bombay cells, since group O cells carry the largest amount of H.

Question 22Blood Group Systems and Immunohematology Theory

A woman is found to have a partial D phenotype such as DVI. What is the clinical consequence?

  1. She cannot form anti-D because D is present
  2. RhIG must not be given to her
  3. Her anti-D would be an autoantibody
  4. She may form anti-D and should be managed as D-negative Correct answer.

Explanation

Partial D individuals lack some D epitopes and can be immunized against the missing ones, producing anti-D that appears to contradict their D-positive typing. For transfusion and pregnancy management they are therefore treated as D-negative, receiving D-negative units and RhIG when indicated.

Question 23Blood Group Systems and Immunohematology Theory

A serum reacts with every panel cell by IAT, while the autocontrol and direct antiglobulin test are both negative. What is the most likely explanation?

  1. A warm autoantibody
  2. An alloantibody to a high-incidence antigen Correct answer.
  3. An antibody to a low-incidence antigen
  4. Rouleaux formation in the serum

Explanation

Uniform reactivity with all panel cells combined with a negative autocontrol indicates an alloantibody directed against a high-prevalence antigen, such as anti-Ge or anti-Jra. Confirmation requires testing rare antigen-negative cells or phenotyping the patient's cells.

Question 24Blood Group Systems and Immunohematology Theory

A group A1 patient with colon carcinoma shows weak agglutination with anti-B reagent, although his own serum anti-B does not react with his cells. What is the most likely explanation?

  1. Acquired B antigen Correct answer.
  2. A2 subgroup with anti-A1
  3. cis-AB inheritance
  4. The Bombay phenotype

Explanation

Acquired B arises in some group A1 patients with gastrointestinal disease when bacterial deacetylase converts the A antigen into a B-like structure. The reactivity is weak, the patient's own anti-B fails to react with his cells, and transfusing group A red cells is appropriate.

Question 25Blood Group Systems and Immunohematology Theory

Serum from a Jk(a−b−) patient reacts with all panel cells except cells of the Jk(a−b−) phenotype. Which antibody is present?

  1. Anti-Jka
  2. Anti-Jkb
  3. Anti-Jk3 Correct answer.
  4. Anti-Ku

Explanation

Jk(a−b−) individuals lack all common Kidd antigens and may be immunized to produce anti-Jk3, which reacts with every cell except other Kidd-null cells. Anti-Jk3 is clinically significant and has been implicated in delayed hemolytic transfusion reactions.

Question 26Antibody Detection and Identification

The indirect antiglobulin test is used to detect red cell antibodies that...

  1. Are naturally occurring ABO antibodies in serum
  2. Bind complement to red cells in vivo
  3. Cause direct agglutination of red cells at room temperature
  4. Sensitize red cells in vitro without agglutinating them Correct answer.

Explanation

The IAT detects IgG alloantibodies that bind to red cells in vitro but are too small to agglutinate them; antihuman globulin cross-links the sensitized cells. IgM antibodies that agglutinate directly are seen in saline phases, not by AHG.

Question 27Antibody Detection and Identification

Why are antibody screen and panel cells usually group O?

  1. To avoid ABO interference Correct answer.
  2. Because they express more Rh antigens
  3. To promote complement activation by IgM
  4. Because they lack all minor antigens

Explanation

Group O cells lack A and B antigens, so antibodies to A or B in the patient's serum do not react with the screening cells. This allows detection of non-ABO red cell antibodies without ABO interference.

Question 28Antibody Detection and Identification

IgG-sensitized control cells are added after AHG reagent to...

  1. Neutralize unbound AHG in the tube
  2. Confirm washing and AHG addition Correct answer.
  3. Supply complement for IgM antibodies
  4. Enhance reactions of weak IgG antibodies

Explanation

Control cells coated with IgG agglutinate only if AHG reagent is present and active, so they verify that AHG was added and that washing removed unbound globulin. They do not enhance or neutralize the test.

Question 29Antibody Detection and Identification

In the tube AHG test, inadequate washing of red cells can cause...

  1. False-negative from complement depletion
  2. False-negative from AHG neutralization Correct answer.
  3. False-positive reactions from rouleaux
  4. False-positive reactions from unbound IgG

Explanation

Residual serum or plasma contains free globulin that can neutralize the added AHG reagent. Without active AHG, IgG-coated cells fail to agglutinate, producing a false-negative result.

Question 30Antibody Detection and Identification

The purpose of LISS in the antibody detection test is to...

  1. Activate complement in the patient serum
  2. Increase the ionic strength of the reaction medium
  3. Destroy IgG antibodies on the red cell surface
  4. Bring red cells and antibodies closer Correct answer.

Explanation

LISS lowers the ionic strength of the medium, reducing the zeta potential and allowing antibodies to come closer to the red cell membrane. This shortens incubation time and can enhance IgG antibody uptake.

Question 31Antibody Detection and Identification

An antibody that reacts only at immediate spin in saline at room temperature is most likely...

  1. IgM, often insignificant Correct answer.
  2. Complement-binding and warm reactive
  3. An autoantibody with high titer
  4. IgG and clinically significant

Explanation

Immediate-spin saline reactions at room temperature are typical of IgM antibodies, many of which are not clinically significant. IgG antibodies usually require AHG testing and react at 37°C or AHG phase.

Question 32Antibody Detection and Identification

A positive autocontrol in the antibody screen suggests that the patient...

  1. Has an autoantibody or in vivo sensitization Correct answer.
  2. Has an alloantibody to a low-incidence antigen
  3. Received no AHG reagent in the test
  4. Was incorrectly typed as group O

Explanation

The autocontrol uses the patient's own red cells with the patient's serum. A positive result indicates that the patient's serum reacts with his or her own cells, which may reflect an autoantibody or in vivo sensitization.

Question 33Antibody Detection and Identification

After a positive antibody screen, the next serologic step is to...

  1. Repeat the ABO type only
  2. Perform a direct antiglobulin test and stop
  3. Perform an antibody identification panel Correct answer.
  4. Transfuse group O blood immediately

Explanation

A positive screen indicates an unexpected red cell antibody, so an antibody identification panel is performed to determine specificity. Additional testing such as a DAT may be useful but does not replace identification.

Question 34Antibody Detection and Identification

Anti-Jka reacts more strongly with Jk(a+b-) cells than with Jk(a+b+) cells. This phenomenon is called...

  1. Cold agglutination
  2. Enzyme dependence
  3. Dosage Correct answer.
  4. A high-incidence antigen

Explanation

Dosage describes stronger reactions with cells homozygous for the corresponding antigen than with heterozygous cells. Kidd antibodies commonly show dosage, so homozygous cells are preferred for detection and exclusion.

Question 35Antibody Detection and Identification

In antibody identification, a panel cell can rule out an antibody specificity when the cell is...

  1. Homozygous for the antigen and nonreactive Correct answer.
  2. Positive for all antigens tested
  3. Heterozygous for the corresponding antigen
  4. Reactive at immediate spin only

Explanation

To exclude an antibody, the cell must express the antigen in homozygous form and give no reaction. Heterozygous cells may give weak or negative reactions because of dosage and are not reliable for exclusion.

Question 36Antibody Detection and Identification

Ficin treatment of panel cells typically destroys the antigen recognized by...

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

Explanation

Ficin and other proteases destroy Duffy antigens, including Fya and Fyb, so anti-Fya reactivity is lost after treatment. Rh and Kidd antigens are generally enhanced or unaffected.

Question 37Antibody Detection and Identification

DTT treatment of red cells is used mainly to...

  1. Destroy IgM and antigens such as Kell Correct answer.
  2. Neutralize warm autoantibodies
  3. Enhance IgG antibody binding
  4. Increase complement activation

Explanation

DTT reduces disulfide bonds and denatures IgM molecules, and it also destroys certain red cell antigens such as Kell and Lutheran. It is useful for distinguishing IgM from IgG reactivity and for assessing Kell-related antibodies.

Question 38Antibody Detection and Identification

Anti-Lea in patient serum can be neutralized by...

  1. Platelets from a group O donor
  2. Pooled group AB serum
  3. Lewis-positive secretor saliva Correct answer.
  4. DTT-treated red cells

Explanation

Lewis substances are soluble in saliva and plasma, so saliva from a Lewis-positive secretor can neutralize anti-Lea. Neutralization helps confirm the specificity when the antibody reacts with all panel cells.

Question 39Antibody Detection and Identification

A patient's serum reacts with all panel cells at room temperature, and the reactions disappear at AHG. The autocontrol is also positive. This pattern most suggests...

  1. An anti-D alloantibody
  2. A warm IgG autoantibody
  3. An anti-K alloantibody
  4. A cold IgM autoantibody Correct answer.

Explanation

Reactivity at room temperature that disappears at AHG is characteristic of a cold-reacting IgM antibody. A positive autocontrol supports an autoantibody, and cold agglutinins commonly react with all adult panel cells.

Question 40Antibody Detection and Identification

Anti-Lea is best detected by testing serum at...

  1. Room temperature with Lewis-positive cells Correct answer.
  2. 37°C with enzyme-treated cells
  3. AHG phase with monospecific anti-IgG
  4. 4°C with DTT-treated cells

Explanation

Anti-Lea is usually an IgM antibody that reacts best at room temperature or immediate spin with Lewis-positive cells. It may bind complement, so polyspecific AHG can also show reactions, but room-temperature testing is key.

Question 41Antibody Detection and Identification

Which antibody is most often associated with hemolytic disease of the fetus and newborn and delayed hemolytic transfusion reactions?

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

Explanation

Anti-K is a clinically significant IgG antibody that can cause hemolytic disease of the fetus and newborn and delayed hemolytic transfusion reactions. Lewis, P1, and I antibodies are usually IgM and not clinically significant in this setting.

Question 42Antibody Detection and Identification

Anti-Jka can be difficult to detect because it...

  1. Binds complement and may elute Correct answer.
  2. Reacts only at 4°C
  3. Occurs only in group AB patients
  4. Is destroyed by LISS

Explanation

Kidd antibodies often bind complement and may elute from red cells, producing weak or variable reactions that can be missed. Testing with homozygous cells and AHG, sometimes with enzyme-treated cells, improves detection.

Question 43Antibody Detection and Identification

Polyspecific AHG reagent contains antibodies to...

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

Explanation

Polyspecific AHG contains anti-IgG and anti-C3d, allowing detection of both IgG-sensitized cells and complement-coated cells. Monospecific AHG contains only one of these antibodies.

Question 44Antibody Detection and Identification

Selected cells are used in antibody identification to...

  1. Determine the patient's ABO type
  2. Measure the antibody titer
  3. Confirm or exclude a suggested specificity Correct answer.
  4. Replace the antibody screen

Explanation

Selected cells have known antigen profiles chosen to confirm or exclude a suspected antibody after the initial panel. They help resolve ambiguous patterns and multiple antibodies.

Question 45Antibody Detection and Identification

A patient's serum reacts with all panel cells at AHG, and the autocontrol is negative. Which approach is most useful for identifying multiple alloantibodies?

  1. Performing only a direct antiglobulin test
  2. Repeating the screen at room temperature
  3. Using only enzyme-treated cells
  4. Test selected cells lacking specific antigens Correct answer.

Explanation

When all panel cells react, the responsible antibodies may be multiple or directed at a high-incidence antigen. Selected cells with known antigen profiles can help separate the specificities and identify which antigens are relevant.

Question 46Antibody Detection and Identification

For a patient with a warm IgG autoantibody and a suspected underlying alloantibody, which procedure is most appropriate before antibody identification if the patient has not been transfused recently?

  1. Neutralization with saliva
  2. DTT treatment of panel cells
  3. Autoadsorption with the patient's cells Correct answer.
  4. Cold autoadsorption at 4°C

Explanation

Autoadsorption removes warm autoantibody from the serum by using the patient's own red cells, leaving any underlying alloantibody for identification. It is preferred when the patient has not been transfused within the previous three months.

Question 47Antibody Detection and Identification

A patient with a warm autoantibody was transfused 2 weeks ago. To remove the autoantibody before identification, the best choice is...

  1. Treatment with polyethylene glycol
  2. Autoadsorption with the patient's red cells
  3. Neutralization with pooled saliva
  4. Alloadsorption with group O red cells Correct answer.

Explanation

Recent transfusion makes autoadsorption unreliable because donor cells in the patient's circulation can adsorb alloantibodies. Alloadsorption with group O cells removes the autoantibody while preserving underlying alloantibodies for identification.

Question 48Antibody Detection and Identification

An eluate prepared from a patient's red cells is used to...

  1. Identify antibodies in the patient's serum
  2. Enhance complement binding in vitro
  3. Neutralize autoantibodies in the serum
  4. Detect in vivo bound antibody Correct answer.

Explanation

An eluate releases antibodies that are bound to red cells in vivo, allowing them to be tested against panel cells. It is useful when the DAT is positive and the serum antibody is not easily identified.

Question 49Antibody Detection and Identification

A patient's serum reacts with all panel cells at AHG, but the autocontrol is negative and the patient's own red cells are compatible with the serum. This pattern most likely indicates...

  1. A warm autoantibody
  2. A cold agglutinin
  3. Antibody to high-incidence antigen Correct answer.
  4. An antibody to a low-incidence antigen

Explanation

Reactivity with all panel cells but not with the patient's own cells indicates that the patient lacks an antigen present on the panel cells. This is the classic pattern of an antibody to a high-incidence antigen.

Question 50Antibody Detection and Identification

A patient's serum reacts with Jk(a+b-) cells but not with Jk(a-b+) cells. Which selected cell pair best confirms anti-Jka and excludes anti-Jkb?

  1. Jk(a-b-) and Jk(a+b+)
  2. Jk(a+b-) and Jk(a-b+) Correct answer.
  3. Jk(a+b-) and Jk(a+b+)
  4. Jk(a+b+) and Jk(a-b+)

Explanation

A Jk(a+b-) cell should react if anti-Jka is present, while a Jk(a-b+) cell should be nonreactive if anti-Jkb is absent. Using both cells separates the two Kidd specificities and supports the identification.