What type of serological testing does the blood
bank technologist perform when determining the
blood group of a patient?
phenotyping
If anti-K
... [Show More] reacts 3+ with a donor cell with a
genotype KK and 2+ with a Kk cell, the antibody
is demonstrating:
Dosage
Carla expresses the blood group antigens Fya, Fyb, and Xga. James shows expressions of none of these antigens. What factor(s) may account for the absence of these antigens in James?
Gender and Race. The frequency of Duffy antigens Fya and Fyb varies
with race. The Fy(a−b−) phenotype occurs in almost
70% of African Americans and is very rare in whites.
The Xga antigen is X-linked and, therefore, expressed more frequently in women (who may inherit the antigen from either parent) than in men.
Which of the following statements is true?
A. An individual with the BO genotype is
homozygous for B antigen
B. An individual with the BB genotype is
homozygous for B antigen
C. An individual with the OO genotype is
heterozygous for O antigen
D. An individual with the AB phenotype is
homozygous for A and B antigens
B. An individual with the BB genotype is
homozygous for B antigen
Which genotype is heterozygous for C?
A. DCe/dce
B. DCE/DCE
C. Dce/dce
D. DCE/dCe
A. DCe/dce
Which genotype(s) will give rise to the Bombay phenotype?
The Bombay phenotype will be expressed only when no H substance is present. The Oh type is expressed by the genotype hh. Bombays produce naturally occurring anti-H, and their serum agglutinates group
O red cells in addition to red cells from groups A, B, and AB persons.
Meiosis in cell division is limited to the ova and sperm producing four gametes containing what complement of DNA?
1N. Meiosis involves two nuclear divisions in succession resulting in four gametocytes each containing half the number of chromosomes found in somatic cells or 1N.
A cell that is not actively dividing is said to be in:
Interphase, The cell is engaged in metabolic activity. Chromosomes are not clearly discerned; however, nucleoli may be
visible
Which of the following describes the expression of most blood group antigens?
Codominant
What blood type is not possible for an offspring of an AO and BO mating?
All are possible
The alleged father of a child in a disputed case of paternity is blood group AB. The mother is group O and the child is group O. What type of exclusion is this?
-Indirect/secondary/second order
An indirect/secondary/second order exclusion occurs when a genetic marker is absent in the child but should have been transmitted by the alleged father. In this case, either A or B should be present in the child.
If the frequency of gene Y is 0.4 and the frequency of gene Z is 0.5, one would expect that they should occur together 0.2 (20%) of the time. In actuality,
they are found together 32% of the time. This is an example of:
Linkage disequilibrium.
Linkage disequilibrium is a phenomenon in which alleles situated in close proximity on a chromosome associate with one another more than would be expected from individual allelic frequencies.
In this type of inheritance, the father carries the trait on his X chromosome. He has no sons with the trait because he passed his Y chromosome to his sons; however, all his daughters will express the trait.
Autosomal Dominant
In the Hardy-Weinberg formula, p2 represents:
In the Hardy-Weinberg formula p2 + 2pq + q2, p2 and q2 represent homozygous expressions and 2pq represents heterozygous expression. This formula is
used in population genetics to determine the frequency of different alleles.
What is the Hardy-Weinberg formula?
p2 + 2pq + q2 = 1
Why do IgM antibodies, such as those formed against the ABO antigens, have the ability to directly agglutinate red blood cells (RBCs) and cause visible agglutination?
IgM antibodies are larger molecules and have the ability to bind more antigen
Which of the following enhancement mediums decreases the zeta potential, allowing antibody and antigen to come closer together?
LISS.
LISS contains a reduced concentration of NaCl (0.2%) and results in a reduction in charged ions within the ionic cloud, decreasing the zeta potential and facilitating antigen and antibody interaction.
This type of antibody response is analogous to an anamnestic antibody reaction.
Secondary.
An anamnestic response is a secondary immune response in which memory lymphocytes respond rapidly to foreign antigen in producing specific antibody. The antibodies are IgG and are produced
at lower doses of antigen than in the primary response.
Which antibodies to a component of complement are contained in the rabbit polyspecific antihuman globulin reagent for detection of in vivo sensitization?
In the DAT (direct antiglobulin test), rabbit
polyspecific antisera contains both an anti-human IgG component and an antibody against the C3d component of complement.
Which of the following distinguishes A1 from A2 blood groups?
A. A2 antigen will not react with anti-A, A1 will
react strongly (4+)
B. An A2 person may form anti-A1; an A1 person
will not form anti-A1
C. An A1 person may form anti-A2, an A2 person
will not form anti-A1
D. A2 antigen will not react with anti-A from a nonimmunized donor; A1 will react with any anti-A
B. An A2 person may form anti-A1; an A1 person will not form anti-A1
A patient's serum is incompatible with O cells. The patient RBCs give a negative reaction to anti-H lectin. What is the most likely cause of these results?
Bombay is the only ABO phenotype incompatible with O cells. The red cells of a Bombay show a negative reaction to anti-H because the cells contain no H substance
What antibodies are formed by a Bombay
individual?
Anti-A, B, and H
Acquired B antigens have been found in:
Group A persons.
Blood is crossmatched on an A positive person with a negative antibody screen. The patient received a
transfusion of A positive RBCs 3 years ago. The donors chosen for crossmatch were A positive.
The crossmatch was run on the Ortho Provue and yielded 3+ incompatibility. How can these results be explained?
The patient is likely an A2 with anti-A1 which is causing reactivity in the crossmatch. A negative antibody screen rules out the possibility of an antibody to a high-frequency antigen, and two
donor units incompatible rules out an antibody to a low-frequency antigen.
A patient's red cells forward as group O, serum agglutinates B cells (4+) only. Your next step would be:
Incubate washed red cells with anti-A1 and
anti-A,B for 30 minutes at room temperature.
The strong 4+ reaction in reverse grouping suggests the discrepancy is in forward grouping. Incubating washed red cells at room temperature with anti-A and anti-A,B will enhance reactions.
Which typing results are most likely to occur when a patient has an acquired B antigen?
A. Anti-A 4+, anti-B-3+, A1 cells neg, B cells neg
B. Anti-A 3+, anti-B neg, A1 cells neg, B cells neg
C. Anti-A 4+, anti-B 1+, A1 cells neg, B cells 4+
D. Anti-A 4+, anti-B 4+, A1 cells 2+, B cells neg
C. Anti-A 4+, anti-B 1+, A1 cells neg, B cells 4+
In forward typing, a 1+ reaction with anti-B is
suspicious because of the weak reaction and the normal reverse grouping that appears to be group A. This may be indicative of an acquired antigen. In the case of an acquired B, the reverse grouping is the
same for a group A person. Choice A is indicative of group AB; choice B is indicative of a group A who may be immunocompromised. Choice D may be
caused by a mistyping or an antibody against antigens on reverse cells.
Which blood group has the least amount of
H antigen?
A1B.
The A1B blood group has the least amount of H antigen. This is due to both A and B epitopes present on red cells compromising the availability of H epitopes. A1B cells will yield weak reactions with anti-H lectin.
Blood groups in order from most to least A antigen:
O, A2, B, A2B, A1, A1B
What type RBCs can be transfused to an A2 person with anti-A1?
A person in need of an RBC transfusion who is an A2 with anti-A1 can be transfused A or O cells because the anti-A1 is typically only reactive at room temperature.
What should be done if all forward and reverse ABO results as well as the autocontrol are positive?
Wash the cells with warm saline, autoadsorb the serum at 4°C.
These results point to a cold autoantibody.
Washing the cells with warm saline may elute the autoantibody, allowing a valid forward type to be performed. The serum should be adsorbed using washed cells until the autocontrol is negative. Then the adsorbed serum should be used for reverse
typing.
What should be done if all forward and reverse ABO results are negative?
All negative results may be due to weakened
antigens or antibodies. Room temperature or lower (4 degree) incubation temperature may enhance expression of weakened antigens or antibodies.
N-acetyl-D-galactosamine is the immunodominant carbohydrate that reacts with
The immunodominant sugar N-acetyl-galactosamine confers A antigen specificity when present at the terminus of the type 2 precursor chain on the RBC
membrane. Therefore, its presence would cause RBCs to react with anti-A1 lectin, Dolichos biflorus.
Ulex europaeus is used for?
H antigen
Vicea graminea is used for?
N antigen
A stem cell transplant patient was retyped when she was transferred from another hospital. What is the most likely cause of the following results?
Patient cells: Anti-A, neg Anti-B, 4+
Patient serum: A1 cells, neg B cells, neg
Immunodeficiency.
A transplant patient is probably taking
immunosuppressive medication to increase graft survival. This can contribute to the loss of normal blood group antibodies as well as other types of antibodies.
What reaction would be the same for an A1 and an A2 person?
A. Positive reaction with anti-A1 lectin
B. Positive reaction with A1 cells
C. Equal reaction with anti-H
D. Positive reaction with anti-A,B
Positive reaction with anti-A,B.
Anti-A,B should react positively with group A or B and any subgroup of A or B (with exception of Am). An A1 (not A2) would react with anti-A1 lectin; only an A2 person with anti-A1 would give a positive reaction with A1 cells; an A2 would react more strongly with anti-H than A1.
A female patient at 28 weeks' gestation yields the following results:
Patient cells: Anti-A, 3+ Anti-B, 4+
Patient serum: A1 cells, neg B cells, 1+ O cells, 1+
Alloantibody in patient serum
The patient is most likely an AB person who has formed a cold-reacting alloantibody reacting with B cells and O cells. An identification panel should be performed. An acquired B person or someone with
hypogammaglobulinemia should not make antibody that would agglutinate O cells.
Which condition would most likely be responsible for the following typing results?
Patient cells: Anti-A, neg Anti-B, neg
Patient serum: A1 cells, neg B cells, 4+
Weak or excessive antigen(s).
Excessive A substance, such as may be found in some types of tumors, may be neutralizing the anti-A. Weak A subgroups may fail to react with anti-A and require
additional testing techniques (e.g., room-temperature incubation) before their expression is apparent
Which of the following results is most likely
discrepant?
Anti-A, neg Anti-B, 4+
A1 cells, neg B cells, neg
Negative A1 cells
The reverse typing should agree with the forward typing in this result. The 4+ reaction with anti-B indicates group B. A positive reaction is expected with A1 cells in the reverse group
A 61-year-old male with a history of multiple
myeloma had a stem cell transplant 3 years ago.
The donor was O positive and the recipient was B positive. He is admitted to a community hospital for fatigue and nausea. Typing results
reveal the following:
Anti-A = 0
Anti-B =0
Anti-A,B = 0
Anti-D = 4+
A1 cells = 4+
B cells = 0
How would you report this type?
Undetermined.
In a transplant scenario, there are no methods to employ to solve the discrepancy. The technologist must rely on the patient history of donor type and recipient type, and the present serological picture. A
B-positive recipient given an O-positive transplant constitutes a minor ABO mismatch. The forward type
resembles the donor. The reverse type still resembles the recipient. The ABO type reported out does not fit
a pattern resulting in an undetermined type.
A complete Rh typing for antigens C, c, D, E, and e revealed negative results for C, D, and E. How is the individual designated?
A. Rh positive
B. Rh negative
C. Positive for c and e
D. Impossible to determine
B. Rh negative
Rh positive refers to the presence of D antigen; Rh negative refers to the absence of the D antigen. These designations are for D antigen only and do not involve other Rh antigens
How is an individual with genotype Dce/dce
classified?
A. Rh positive
B. Rh negative
C. Rhnull
D. Total Rh
This individual has the D antigen and is classified as Rh positive. Any genotype containing the D antigen will be considered Rh positive
If a patient has a positive direct antiglobulin test, should you perform a weak D test on the cells?
A. No, the cells are already coated with antibody
B. No, the cells are Rhnull
C. Yes, the immunoglobulin will not interfere with
the test
D. Yes, Rh reagents are enhanced in protein media
No, the cells are already coated with antibody.
If a person has a positive DAT, the red cells are coated with immunoglobulin (anti-IgG and anti- C3d, or both). If a test for weak D were performed, the test would yield positive results independent of
the presence or absence of the D antigen on the red cells.
Which donor unit is selected for a recipient with anti-c?
A. r´r
B. R0R1
C. R2r´
D. r´ry
D. r´ry
Which genotype usually shows the strongest
reaction with anti-D?
A. DCE/DCE
B. Dce/dCe
C. D-/D-
D. -CE/-ce
C. D-/D-
The phenotype that results from D-/D- is classified as enhanced D because it shows a stronger reaction than expected with anti-D. Such cells have a greater
amount of D antigen than normal. This is thought to result from a larger quantity of precursors being available to the D genes because there is no competition from other Rh genes
Why is testing for Rh antigens and antibodies different from ABO testing?
ABO reactions are primarily due to IgM
antibodies and usually occur at room
temperature; Rh antibodies are IgG and
agglutination usually requires a 37°C incubation and enhancement media
Testing reveals a weak D that reacts 1+ after
indirect antiglobulin testing (IAT). How is this
result classified?
Blood tested for weak D that shows 1+ reaction after IAT is classified as Rh positive. The weak D designation is not noted in the reporting of the result.
What is one possible genotype for a patient who
develops anti-C antibody?
A. R1r
B. R1R1
C. r´r
D. rr
D. rr
Only rr (dce/dce) does not contain C antigen. A person
will form alloantibodies only to the antigens he or she
lacks.
A patient developed a combination of Rh
antibodies: anti-C, anti-E, and anti-D. Can
compatible blood be found for this patient?
A. It is almost impossible to find blood lacking the
C, E, and D antigens
B. rr blood could be used without causing a
problem
C. R0R0 may be used because it lacks all three
antigens
D. Although rare, ryr blood may be obtained from
close relatives of the patient
B. rr blood could be used without causing a
problem
The genotype rr (dce/dce) lacks D, C, and E antigens and would be suitable for an individual who has developed antibodies to all three antigens. This is the most common Rh-negative genotype and is found in nearly 14% of White blood donors.
A patient tests positive for weak D but also
appears to have anti-D in his serum. What may be the problem?
A. Mixup of samples or testing error
B. Most weak D individuals make anti-D
C. The problem could be due to a disease state
D. A D mosaic may make antibodies to missing antigen parts
D. A D mosaic may make antibodies to missing antigen parts
Which offspring is not possible from a mother who is R1R2 and a father who is R1r?
A. DcE/DcE
B. Dce/DCe
C. DcE/DCe
D. Dce/dce
A. DcE/DcE
DcE/DcE (R2R2) is not possible because R2 can be
inherited only from the mother and is not present in
the father.
Why is testing a pregnant woman for weak D not required?
An Rh-positive fetus may yield false positive
results in a fetal maternal bleed
If a weak D test is performed on a pregnant woman with no previous history, a false-positive weak D test may result from the presence of fetal blood if the fetus is Rh positive. A pregnant woman with weak D may be given Rh immune globulin without any harmful consequences. Therefore, weak D testing of pregnant women is not necessary.
What antibodies could an R1R1 make if exposed to R2R2 blood?
The R1R1 (DCe/DCe) individual does not have the E or c antigen, and could make anti-E and anti-c antibodies when exposed to R2R2 cells (DcE/DcE).
What does the genotype —/— represent in the Rh system?
A. Rh negative
B. D mosaic
C. Rhnull
D. Total Rh
Rh null
A person who is Rhnull shows no Rh antigens on his or her RBCs. Loss of Rh antigens is very unlikely to happen because Rh antigens are integral parts of the RBC membrane. The Rhnull phenotype can result
from either genetic suppression of the Rh genes or inheritance of amorphic genes at the Rh locus.
What techniques are necessary for weak D testing?
A. Saline + 22°C incubation
B. Albumin or LISS + 37°C incubation
C. Saline + 37°C incubation
D. 37°C incubation + IAT
D. 37°C incubation + IAT
Weak D testing requires both 37°C incubation and the IAT procedure. Anti-D is an IgG antibody, and attachment of the D antigen is optimized at warmer temperatures. Antihuman globulin in the IAT phase facilitates lattice formation by binding to the antigen-antibody complexes.
Weak D procedure
Prepare a washed, 3% suspension of patient cells, and set up the D and DC (Rh Control) tubes, if not already done. (SEE ABO/Rh TYPING PROCEDURE)
Record the D and DC immediate spin results. If the Rh test is negative, continue with step 3.
Incubate both tubes at 37oC for 15 to 30 minutes.
Centrifuge and read for agglutination as usual. If the Rh test is negative, continue with step 5.
Wash both tubes 3-4 times with saline.
Immediately after the last wash, add one drop Coombs serum to each tube and centrifuge in the serofuge the time appropriate for the Coombs spin calibration.
Immediately resuspend gently and examine for agglutination using the lighted agglutination viewer.
Record results in the appropriate column on the worksheet
Confirm all negative results by adding one drop Coombs control cells to all tubes showing no agglutination and centrifuge 15-30 seconds at high speed in the serofuge.
Gently resuspend and examine for agglutination. Agglutination should be present in this step or the test is invalid.
Weak D Results Interpretation
A negative result in the immediate spin phase but agglutination in the D tube following incubation (with no agglutination in the DC tube) indicates a positive test for weak D. Lack of agglutination is a negative test and the patient is considered truly D negative. Agglutination in the DC tube invalidates the test.
A true weak D should give at least a 2+ positive result. Weaker results may be due to mixed field agglutination in an Rh negative individual who received Rh positive blood, or vice-versa. Obtain a recent transfusion history on patients who give inconclusive weak D results
A patient types as AB and appears to be Rh
positive on slide typing. What additional tests
should be performed for tube typing?
A. Rh negative control
B. Direct antiglobulin test (DAT)
C. Low-protein Rh antisera
D. No additional testing is needed
An Rh-negative control (patient cells in saline or
6% albumin) should be run if a sample appears to be AB positive. The ABO test serves as the Rh control for other ABO types.
According to the Wiener nomenclature and/or
genetic theory of Rh inheritance:
A. There are three closely linked loci, each with a
primary set of allelic genes
B. The alleles are named R1, R2, R0, r, r´, r˝, Rz,
and ry
C. There are multiple alleles at a single complex
locus that determine each Rh antigen
D. The antigens are named D, C, E, c, and e
C. There are multiple alleles at a single complex
locus that determine each Rh antigen
The Wiener nomenclature for the E antigen is:
A. hr´
B. hrv´
C. rh˝
D. Rh0
C. rh˝
The Wiener designation for the E antigen is rh˝. The Wiener designation hr´ denotes c, hr˝ denotes e, and Rh0 is D.
A patient has the Lewis phenotype Le(a−b−). An
antibody panel reveals the presence of anti-Lea.
Another patient with the phenotype Le(a−b+) has
a positive antibody screen; however, a panel
reveals no conclusive antibody. Should anti-Lea be considered as a possibility for the patient with the Le(a−b+) phenotype?
Anti-Lea is not a likely antibody because even Leb individuals secrete some Lea.
Anti-Lea is produced primarily by persons with the
Le(a−b−) phenotype because Le(a−b+) persons still
have some Lea antigen present in saliva. Although Lea
is not present on their red cells, Le(a−b+) persons do
not form anti-Lea. [Show Less]