4 TESTING FOR ANTIBODIES Flashcards
(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
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(ab+) 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.
(2) A medical laboratory scientist (MLS) is having great difficulty resolving an antibody mixture. One of the antibodies 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 clinical 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
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.
(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
A. Blood that is negative for Leb antigen
Lewis antibodies are generally not considered clinically significant unless they react at 37°C or at the IAT phase. The antibody must be honored in this scenario due to its reactivity at the IAT phase of testing.
(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
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 heterozygous 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 MM or NN genotype, which carry a greater amount of the corresponding antigen.
(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
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.
(6) A patient is suspected of having paroxysmal cold hemoglobinuria (PCH). Which pattern of reactivity is characteristic of the Donath-Landsteiner antibody, which causes this condition?
A. The antibody attaches to RBCs at 4°C and causes hemolysis at 37°C
B. The antibody attaches to RBCs at 37°C and causes agglutination at the IAT phase
C. The antibody attaches to RBCs at 22°C and causes hemolysis at 37°C
D. The antibody attaches to RBCs and causes agglutination at the IAT phase
A. The antibody attaches to RBCs at 4°C and causes hemolysis at 37°C
The Donath-Landsteiner antibody has anti-P specificity with biphasic activity. The antibody attaches to RBCs at 4°C and then causes the RBCs to hemolyze when warmed to 37°C.
(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
D. Neutralization with hydatid cyst fluid
Hydatid cyst fluid contains P1 substance, which can neutralize anti-P1 antibody.
(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
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.
(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
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.
(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
C. Anti-M, anti-N
Antibodies to the M and N antigens are IgM antibodies commonly found as cold agglutinins.
(11) Which of the following antibodies characteristically gives a refractile mixed-field appearance?
A. Anti-K
B. Anti-Dia
C. Anti-Sda
D. Anti-s
C. Anti-Sda
Anti-Sda characteristically gives a refractile mixed field agglutination reaction in the IAT phase. The refractile characteristic is more evident under the microscope.
(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
C. 95% confidence that the correct antibody has been identified
The 3+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.
(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
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.
(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
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.
(15) Which characteristics are true of all three of the following antibodies: anti-Fya, antiJka, 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 detected 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
A. Detected at the IAT phase; may cause hemolytic disease of the fetus and newborn (HDFN) and hemolytic transfusion reactions
Anti-Fya, 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.
