4.4 Testing for Antibodies

Question 1

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 a possibility for the patient with the Le(a-b+) phenotype?
A. Anti-Lea should be considered as a possible antibody
B. Anti-Lea may be a possible antibody, but further studies are needed
C. Anti-Lea is not a likely antibody because even Leb individuals secrete some Lea
D. Anti-Lea may be found in saliva but not detectable in serum

Answer 1

C. 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 RBCs, Le(a-b+) persons do not form anti-Lea.

Question 2

A medical laboratory scientist (MLS) is having great difficulty resolving an antibody mixture. One of the antibody is anti-Lea. This antibody is not clinically significant in this situation, but it needs to be removed to reveal the possible presence of an underlying antibody of clincial significance. What can be done?
A. Perform an enzyme panel
B. Neutralize the serum with saliva
C. Neutralize the serum with hydatid cyst fluid
D. Use dithiothreitol (DTT) to treat the panel cells

Answer 2

B. Neutralize the serum with saliva

Saliva from an individual with the Le gene contains the Lea antigen. This combines with anti-Lea, neutralizing the antibody. Panel cells treated with DTT (0.2M) lose reactivity with anti-K and other antibodies, but not anti-Lea. Hydatid cyst fluid neutralizes anti-P1.

Question 3

What type of blood should be given to an individual who has anti-Leb that reacts 1+ at the IAT phase?
A. Blood that is negative for Leb antigen
B. Blood that is negative for both Lea and Leb antigens
C. Blood that is positive for Leb antigen
D. Lewis antibodies are not clinically significant, so any type of blood may be given.

Answer 3

A. Blood that is negative for Leb antigen

Lewis antibodies are generally not consideredd clinically significant unless they react at 37C or at the IAT phase. The antibody must be honored in this scenario due to its reactivity at the IAT phase of testing.

Question 4

Which of the following statements is true concerning the MN genotype?
A. Antigens are destroyed using bleach-treated cells
B. Dosage effect may be seen for both M and N antigens
C. Both M and N antigens are impossible to detect because of cross-interference
D. MN is a rare phenotype seldom found in routine antigen typing

Answer 4

B. Dosage effect may be seen for both M and N antigens

Dosage effect is the term used to describe the phenomenon of an antibody that reacts more strongly with homozygous cells than with heteroygous cells. Dosage effect is a characteristic of the genotype MN because the M and N antigens are both present on the same cell. This causes a weaker reaction than seen with RBCs of either the MN or NN genotype, which carry a greater amount of the corresponding antigen.

Question 5

**Anti-M is sometimes found with reactivity detected at the immediate spin (IS) phase that persists in strength to the IAT phase. What is the main testing problem with a strong anti-M? **
A. Anti-M may not allow detection of a clinically significant antibody
B. Compatible blood may not be found for the patient with a strongly reacting anti-M
C. Anti-M cannot be removed from serum
D. Anti-M may react with the patient’s own cells, causing a positive autocontrol

Answer 5

A. Anti-M may not allow detection of a clinically significant antibody

Although anti-M may not be clinically significant, a strongly reacting anti-M that persists through to the IAT phase may interfere with detection of a clinically significant antibody that reacts only at IAT.

Question 6

A patient is suspected of having paroxysmal cold hemoglobinuria (PCH). Which pattern of reactivity is characteristc of the Donath-Landsteiner antibody, which causes this condition?
A. The antibody attaches to RBCs at 4C and causes hemolysis at 37C
B. The antibody attaches to RBCs at 37C and causes agglutination at the IAT phase
C. The antibody attaches to RBCs at 22C and causes hemolysis at 37C
D. The antibody attaches to RBCs and causes agglutination at the IAT phase

Answer 6

A. The antibody attaches to RBCs at 4C and causes hemolysis at 37C

The Donath-Landsteiner antibody has anti-P specificity with biphasic activity. The antibody attaches to RBCs at 4C and then causes the RBCs to hemolyze when warmed to 37C.

Question 7

How can interfering anti-P1 antibody be removed from a mixture of antibodies?
A. Neutralization with saliva
B. Agglutination with human milk
C. Combination with urine
D. Neutralization with hydatid cyst fluid

Answer 7

D. Neutralization with hydatid cyst fluid

Hydatid cyst fluid contains P1 stubstance, which can neutralize anti-P1 antibody.

Question 8

Which antibody is frequently seen in patients with warm autoimmune hemolytic anemia (WAIHA)?
A. Anti-Jka
B. Anti-e
C. Anti-K
D. Anti-Fyb

Answer 8

B. Anti-e

Anti-e is frequently implicated in cases of WAIHA. The corresponding antigen is characterized as high frequency in the Rh system and can mask the presence of other alloantibodies.

Question 9

** A patient’s antibody shows strong reactions in all test phases. All screen and panel cells are positive. Serum is then tested with a cord blood cell, and the reaction is negative. What antibody is suspected?**
A. Anti-I
B. Anti-i
C. Anti-H
D. Anti-p

Answer 9

A. Anti-I

Adult cells contain mostly I antigen, and anti-I would react with all adult cells found on screen or panel cells. Cord blood cells, however, contain mostly i antigen and would test negative or only weakly positive with anti-I.

Question 10

Which group of antibodies is commonly found as cold agglutinins?
A. Anti-K, anti-k, anti-Jsb
B. Anti-D, anti-e, anti-C
C. Anti-M, anti-N
D. Anti-Fya, anti-Fyb

Answer 10

C. Anti-M, and anti-N

Antibodies to the M and N antigens are IgM antibodies commonly found as coldd agglutinins.

Question 11

Which of the following anti-bodies characteristically gives a refractile mixed-field appearance?
A. Anti-K
B. Anti-Dia
C. Anti-Sda
D. Anti-s

Answer 11

C. Anti-Sda

Anit-Sda characteristically gives a refractile mixed field agglutination reaction in the IAT phase. The refractile charactersitic is more evident under the microscope.

Question 12

What does the 3+3 rule ascertain?
A. An antibody is ruled in
B. An antibody is ruled out
C. 95% confidence that the correct antibody has been identified
D. 95% confidence that the correct antibody has not been identified

Answer 12

C. 95% confidence that the correct antibody has been identified

The 3+# rule ascertains correct identification of antibody at a confidence level of 95%. For this level to be met, reagent RBCs are found containing target antigen to suspected antibody that react in test phase; likewise, reagent RBCs devoid of antigen will not react in test phase.

Question 13

The k (Cellano) antigen is a high-frequency antigen and is found on most RBCs. How often would one expect to find the corresponding antibody?
A. Often, because it is a high-frequency antibody
B. Rarely, because most individuals have the antigen and therefore would not develop the antibody
C. Depends on the population, because certain racial and ethnic groups show a higher frequency of anti-k
D. Impossible to determine without consulting regional blood group antigen charts

Answer 13

B. Rarely, because most individuals have the antigen and therefore would not develop the antibody

k antigen is found with a frequency of 99.8%; therefore, k-negative individuals are rare. Because of this, the occurrence of anti-k is also rare.

Question 14

Which procedure would help to distinguish between anti-e and anti-Fya in an antibody mixture?
A. Lowering the pH of test serum
B. Running an enzyme panel
C. Using a thiol reagent
D. Running an LISS panel

Answer 14

B. Running an enzyme panel

Enzyme-treated cells will not react with Duffy antibodies. Rh antibodies react more strongly with enzyme-treated RBCs. An enzyme panel, therefore, would enhance reactivity of anti-e and destroy reactivity to anti-Fya.

Question 15

Which characteristics are true of all three of the following antibodies: anti-Fya, and anti-JKa, and anti-K?
A. Detected at the IAT phase; may cause hemolytic disease of the fetus and newborn (HDFN) and hemolytic transfusion reactions
B. Not detectedd with enzyme-treated cells
C. Requires the IAT technique for detection; usually not associated with HDFN
D. Enhanced reactivity with enzyme-treated cells; may cause severe hemolytic transfusion reactions

Answer 15

A. Detected at the IAT phase; may cause hemolytic disease of the fetus and newborn (HDFN) and hemolytic transfusion reactions

Anti-Fya, and anti-Jka, and anti-K are usually detected at IAT and all may cause HDFN and transfusion reactions that may be hemolytic. Reactivity with anti-Fya is lost with enzyme-treated RBCs, but reactivity with anti-Jka is enhanced with enzyme-treated cells. Reactivity with anti-K is unaffected by enzyme-treated cells.

Question 16

A patient is admitted to the hospital. Medical records indicate that the patient has a history of anti-Jka. When you performed the type and screen, the type was O positive, and the screen was negative. You should:
A. Crossmatch using units negative for Jka antigen
B. Crossmatch random units, since the antibody is not demonstrating
C. Request a new sample
D. Repeat the screen with enzyme-treated screening cells

Answer 16

A. Crossmatch using units negative for Jka antigen

The Kidd antibodies are notorious for disappearing from serum, yielding a negative result for the antibody screen. If a patient has a history of a Kidd antibody, blood must be crossmatched using antigen-negative units. If the patient is transfused with the corresponding antigen, an anamnestic response may occur with a subsequent hemolytic transfusion reaction.

Question 17

An MLS performs an antibody study and finds 1+ and weak positive reactions for several of the panel cells. The reactions do not fit a pattern. Several selected panels and a patient phenotype do not reveal any additional information. Serum is diluted and retested, but the same reactions persist. What type of antibody may be causing these results?
A. Antibody to a high-frequency antigen
B. Antibody to a low-frequency antigen
C. High titer low avidity (HTLA)
D. Anti-human leukocyte antigen (anti-HLA)

Answer 17

C. High titer low avidity (HTLA)

HTLA antibodies may persist in reaction strength, even when diluted. These antibodies are directed against high-frequency antigens (e.g., Cha). They are not clicially significant but, when present, are responsible for a high incidence of incompatible crossmatches.

Question 18

An antibody is detected in a pregnant woman and is suspected of being the cause of fetal distress. The antibody reacts at the IAT phase but does not react with DTT-treated cells. This antibody causes in vitro hemolysis. What is the most likely antibody specificity?
A. Anti-Lea
B. Anti-Lua
C. Anti-Lub
D. Anti-Xga

Answer 18

C. Anti-Lub

Of the antibodies listed, only Lub is detected in the IAT phase, causes in vitro hemolysis, may cause HDFN, and does not react with DTT-treated cells.

Question 19

What sample is best for detecting complement-dependent antibodies?
A. Plasma stored at 4C for no longer than 24 hours
B. Serum stored at 4C for no longer than 48 hours
C. Either serum or plasma stored at 20C to 24C no longer than 6 hours
D. Serum heated at 56C for 30 minutes

Answer 19

B. Serum stored at 4C for no longer than 48 hours

Serum stored 4C for no longer than 48 hours preserves complement activity. Plasma is inappropriate because most anticoagulants chelate calcium needed for activation of complement. Heating the serum to 56C destroys complement. Heating the serum to 56C destroys complement.

Question 20

Which antibody would not be detected by group O screening cells?
A. Anti-N
B. Anti-A1
C. Anti-Dia
D. Anti-k

Answer 20

B. Anti-A1

ABO antibodies are not detected by group O screening cells because O cells contain no A or B antigens.

Question 21

Refer to Panel 1. Which antibody is most likely implicated?
A. Anti-Fyb
B. Anti-Jkb
C. Anti-e
D. Anti-c and anti-K

Answer 21

B. Anti-Jkb

The pattern clearly fits that of anti-Jkb, an antibody that usually reacts best at IAT. The weaker reactions are caused by the dosage effect found on cells that are heterozygous for the Jkb antigen.

Question 22

Refer to Panel 2. Which antibody specificity is most likely present?
A. Anti-S and anti-E
B. Anti-E and anti-K
C. Anti-Lea and anti-Fyb
D. Anti-C and anti-K

Answer 22

D. Anti-C and anti-K

Question 23

On Panel 2, which of the following antibodies cound not be ruled out?
A. Anti-Jkb
B. Anti-C
C. Anti-M
D. Anti-Fyb

Answer 23

B. Anti-C

Question 24

On the Panel 2, Which cells are homozygous for C?
A. 1, 2, 3
B. 1, 2, 9
C. 3, 4, 7

Answer 24

B. 1, 2, 9

On the panel cells, 1, 2, and 9 antigen is present and c antigen is absent, rendering the cells homozygous for C.

Question 25

A 77 year old female is admitted to a community hospital after a cardiac arrest. History includes an abdominal aortic aneurysm 2 years ago for which received 6 units of packed RBCs. Her blood type is A positive, and the antibody screen is positive at the AHG phase in screening cells II and III. A panel is performed by using LISS. In Panel 3, which antibodies are likely implicated?
A. C and K
B. Jka and c
C. E and c
D. Fya and M

Answer 25

C. E and c

The antibodies evident in Panel 3 are E and c. Every positive reaction at 37C and IAT phases are positive for either E antigen and/or for cells homozygous for c antigen.

Question 26

What observation is apparent with one of the antibodies present on Panel 3?
A. One antibody is only reacting with heterozygous cells
B. Both antibodies are only reacting with homozygous cells
C. One antibody is only reacting with homozygous cells
D. Both antibodies are exhibiting dosage

Answer 26

C. One antibody is only reacting with homozygous cells

Anti-c is only reacting with homozygous cells.