Pre-Transfusion Testing and Antibody ID Flashcards
A patient has a positive antibody screen and a positive antibody identification panel. All tested cells are positive 3+ at the AHG phase of reactivity, including the autocontrol. The patient has never been transfused or pregnant.
Which adsorption technique would you use to complete the case?
a. cold alloadsorption
b. cold autoadsorption
c. warm alladsorption
d. warm autoadsorption
d. warm autoadsorption
The antibody reacts at the AHG phase of testing, which indicates a warm antibdoy and the adsorption should take place at 37 C.
Since the patient has not been transfused or pregnant in the last 3 months, an autoantibody is suspected and the patients own autologous cells can be used to conduct the adsorption. The autoadsorption will act to “Soak Up” the autoantibody and leave behind the serum that can then be used to screen for additional antibodies (the “left behind” serum is known as “adsorpbed serum”).
Performing an autoadsorption over an alladsorption is preferred when possible because the patient’s own cells do not run the risk of adsorbing out any clinically significant antibodies.
You identify an RBC alloantibody in a patient. Which antibody would be eligible for antibody screens and crossmatches using the prewarm technique?
a. anti-E reacting at 37 C and AHG
b. anti-S reacting at AHG using LISS and PEG
c. anti-K reacting at PEG AHG
d. anti-M reacting at immediate spin, 37 C and weak at the AHG phase.
e. anti-M reacting at the AHG phase
d. anti-M reacting at immediate spin, 37 C and weak at the AHG phase.
Anti-M is usually an IgM cold-reacting antibody. When testing is performed at IS, 37 C, and AHG, the IgM pentamer can bind strongly and carry through all phases of testing. Once an antibody in this category is identified, you can use the prewarm technique to provide compatible RBCs for transfusion to the patient if the antibody may be causing interference at the AHG phase. The prewarm technique allows you to provide these RBCs without phenotyping the RBCs for the corresponding antigen against the patient antibody.
If the antibody in question still shows agglutination at the AHG phase of testing using the prewarm technique, you must provide the patient with RBCs that are antigen typed for the corresponding antigen against the patient antibody.
anti-M, which is usually IgM, may contain an IgG component that can cause this problem.
NOTE THE SECOND SENTENCE ABOVE! This advice applies after the antibody is identified! It is usually poor practice to simple “PreWarm” an unknown cold-reacting antibody without having an idea of what it is. Some cold-reacting antibodies can have wide thermal amplitudes an cause significant hemolysis, so the PreWarm technique should not be used as a substitute for proper antibody identification.
What is the purpose of Coombs’ controll cells?
a. To ensure that AHG reactions are not false-negatives
b. to ensure that washing removed all unbound antibody
c. to ensure that AHG was not omitted or inactivated.
d. All the above
d. All the above
What is an elution?
a. A technique used to dissociate IgM or IgG antibodies form sensitized RBCs.
b. A technique used to determine if a patient is a sickler.
c. A technique used to reduce the zeta potential inhancing antigen binding.
d. none of the above.
a. A technique used to dissociate IgM or IgG antibodies form sensitized RBCs.
When performing the elution procedure, what is the solution containing the recovered antibody called?
a. Neutralized serum
b. The buffer
c. The eluate
d. Absorbed serum
c. The eluate
Acid is added to the red cells which will elute off the antibody. Once antibody has been eluted, the red cells are discarded and a buffer added to make the eluate containing the antibodies to make it an opitmial pH for testing,
The process of removing antibdoy from serum by combining serum sample with appropriate red cells under optimal conditions is called:
a. Elution
b. Absorption
c. Enzyme treatment
d. Sensitization
b. Absorption
The target antibody will be removed from the serum and attach to the red blood cells
Routine pre-transfusion testing consists of all of the following except:
a. ABO typing
b. Rh typing
c. Antibody Screen
d. DAT
d. DAT
Autocontrol and DATS are not required per AABB Standards and are performed per each facilities procedures.
What is the most common use of adsorption?
a. Removal of plasma protein from patient serum.
b. Removal of alloantibody from patient serum.
c. Removal of autoantibody from patient serum.
d. Removal of drug-induced antibody form patient serum.
c. Removal of autoantibody from patient serum.
The most common use of an adsoprtion is to remove autoantibodies from serum that could be hiding clinically significant alloantibodies.
Other uses can include removing a specific alloantibody to allow for performing rule-outs or rule-ins for other alloantibodies or differential adsorptions/elutions to identify the specificity of an antibody (ex. G differential).
Anti-drug antibodies cannot be adsorbed out of the serum; some monoclonal drugs that attach to specific CD proteins may be able to be absorbed out but this is not usually the best method.
In what circumstance would an alloadsorption be performed?
a. Warm autoantibody in serum
b. HDN
c. Multiple antibodies in serum
d. Hemolytic transfusion reaction
c. Multiple antibodies in serum
Removing an antibody, such as anti-k that is against a high frequency antigen, can allow for easier detection of other alloantibdoies and to rule out other common clinically significant alloantibodies.
A patient with anti-K was crossmatched with 4 units of ABO/Rh compatible, K-negative donor blood. The units were compatible in all phases of testing. After the antiglobulin phase. IgG sensitized control cells were added and a 2+ reaction was noted. The proper interpretation of this 2+ reaction is that the:
a. cell washing was adequate
b. Crossmatch was performed properly
c. Patient’s serum was added
d. Crossmatched units were K Positive
e. all of the above
a. cell washing was adequate
Coombs control cells only tell you if:
- The RBCs were washed properly
- The anti-human globulin was added
- The anti-human globulin worked properly (was not neutralized)
It does not tell you if the entire test was performed correctly. It cannot detect, for example, If any reagent (serum, enhancement, etc.) was omitted. If the correct check cells were used, or if the testing was performed at the right temperature.
Which of the following antigens are not required to be on reagent screening cells?
a. Jsa
b. D
c. Fyb
d. C
a. Jsa
Jsa is a low frequency antigen and is not required by the FDA to be on the selected cells. The D, C, and Fyb antigens are required by the FDA to be on the selected cells and panels.
In what test might rouleaux cause an interference?
a. DAT
b. Forward ABO typing
c. Reverse ABO typing
d. Rh control
c. Reverse ABO typing
Rouleaux is an issue found in the patient’s serum. Reverse ABO testing tests with serum so rouleaux can interfere with testing.
The DAT forward ABO and Rh control are all testing the patient’s red cell antigens and not the patients antibodies (serum).
In interpreting an antibody screen, which of the following questions might be asked to decipher the class of antibody?
a. Is the autologous control positve or negative?
b. Is hemolysis present?
c. In what phase did the reaction occur?
d. Is rouleaux present?
c. In what phase did the reaction occur?
A reaction at colder temperatures (4 C, RT, IS, 22 C) or warmer temperatures (37 C/AHG) will give you an idea as to what class (IgM or IgG) the antibody belongs to.
If your auto control is positive or negative, the phase where the control is positive at will still need to be evaluated to determine if it is a cold or warm antibody.
Why are screening cells group O?
a. To prevent interference from anti-A and anti-B antibodies in patient serum
b. To prevent interference with A and B antigens on patient cells
c. Because group O cells are easier to acquire in random populations.
d. Because of group O cells contain antigens to clinically significant antibodies.
a. To prevent interference from anti-A and anti-B antibodies in patient serum
Screening and panel cells are group O because a group O person does not have A and B antigens. This allows for patients of all blood groups to be tested with the same panels (easy to remember because group O is the universal RBC donor for this same reason). If you are testing a patient that is group A, B or AB, their naturally occurring anti-A and anti-B will not being to the screening/panel cells.
Why is it important for screening cells to be from individuals who have homozygous expression of antigens?
a. Homozygous expression is directly related to clinically significant antibodies.
b. Stronger reactions are seen with heterozygous cells than with homozygous cells.
c. Weakly reacting antibodies may not agglutinate heterozygous cells.
d. All of the above
c. Weakly reacting antibodies may not agglutinate heterozygous cells.
All other statements are false. Homozygous expression is not directly related to clinically significant antibodies, nor do you see stronger reactions with heterozygous cells than with homozygous cells. Remember homozygous cells have a stronger expression than heterozygous cells.
Double dose is the correct term vs homozygous and single dose vs heterozygous: however. like “anti-Kell” instead of anti-K or -K1, some terminology just sticks around in blood bank. Be aware when you’re looking at a panel and the reagent cell appears like it could be from someone of black ethnicity, it’s possible their duffy antigen may appear to be homozygous but really it is only a single dose due to the GATA mutation.
Serum containing anti-D, -C and -G was adsorbed onto a r’ red cell.
An eluate prepared from the r’ cells would contain which antibodies?
a. anti-G
b. anti-D and anti-G
c. anti-C
d. anti-C and anti-G
d. anti-C and anti-G
The serum contains all three antibodies: -D, -C, and -G and is going to be absorbed onto r’ cells. Recall r’ cells are D-,C+ and G+. Because the D antigen is not present, anti-D will remain in the patient’s serum but anti-C and -G will be absorbed onto the r’ red cells.
An elution will remove the absorbed antibodies, which means the eluate will contain anti-C and anti-G. Remember the G antigen is present on D AND C positive cells, so if the eluate was tested with a panel, reactivity would still be observed with d and C positive red cells.
In the direct antiglobulin test (DAT), the antiglobulin reagent is used to:
a. detect pre-existing antibodies on erythrocytes
b. measure antibodies in a test serum by fixing complement.
c. precipitate anti-erythrocyte antibodies
d. mediate hemolysis of indicator red blood cells by providing complement.
a. detect pre-existing antibodies on erythrocytes
In the DAT, the RBCs are washed then the anti-human globulin reagent (AHG) is added followed by the tube being spun then read for agglutination. This test detects the presence of antibodies which were already bound to the surface of the red cell in vivo (in the patient’s body.
Contrast this with the indirect antiglobulin test (IAT) in which the RBCs are incubated first with patient serum or commercial reagent in an attempt to bind antibodies to the RBCs, then washed, AHG added, spun and read. The IAT detects the presence of antibodies which were bound in-vitro (outside of the patient’s body in the test system)
What is the most appropriate control for a positive direct antiglobulin test?
a. check cells and antihuman globulin
b. patient cells and antihuman globulin
c. check cells and saline
d. patient cells and saline
d. patient cells and saline
When all of the DAT tests are positive, it is prudent to test a DAT control to be sure that the patient cells are not spontaneously agglutinating in the test system. Therefore, test the patient cells in a neutral medium (one that does not contain antibodies).
Of those listed, the best choice is patient cells and saline. Some facilities will test patient cells in diluted albumin, which is acceptable as well.
You have a serum sample which has anti-e, anti-Fya, and anti-JKa. The goal is to remove the anti-Fya specificity from the serum sample. Which cell below is the best choice to use as an absorbing cell?
a. e+, Fy(a)-, Jk(a)+
b. e-, Fy(a)-, Jk (a) -
c. e-, Fy(a) +, Jk (a)-
d. e-, Fy(a)-,Jk(a)+
c. e-, Fy(a) +, Jk (a)-
To remove the anti-Fya forma mixture of anti-e, antiFya, and anti-Jka, pick a cell that has only the Fya antigen and lacks the e and Jka antigens. Remember that the question said the goal was to remove the anti-Fya specificity only.
The other choices would either remove an additional antibody or leave the anti-Fya behind.
A patient is tested, and the following results are obtained:
ABO/RH: O Positive
Antibody Screen:
Screening Cell IAT Check Cells
SCI 2+ NA
SCII 2+ NA
SCIII 2+ NA
Autocontrol 2+ NA
Of the choices below, which tpe of eluate is the best choice for the next phase of testing?
a. Freeze-Thaw
b. Cold-Acid
c. Ether
d. Heat (56 C)
b. Cold-Acid
Of the eluate procedures listed, the cold acid is the best choice. An example of the cold acid is the ELUKIT, a commercially made eluate kit. From the screening cell results, it appears to be a warm autoantibody of broad specificity. Choose an elution procedure that givevs a good recovery for this type of antibody.
Freeze-Thaw and Heat eluate techniques are good for ABO antibodies, but not for other blood group antibodies.
Ether is a hazardous substance. While it does offer a good recovery of warm reacting antibodies, it’s hazards far outweigh its technical benefits.
A 56 year old female with cold hemagglutinin disease has a positive direct antiglobulin test (DAT). When the DAT is repeated using monospecific antiglobulin sera, which of the following is most likely to be detected.
a. IgM
b. IgG
c. C3d
d. C4d
c. C3d
This patient has a cold hemagglutinin, so complement (or C3d) would be the most likely to be detected coating the RBCs.
The antibody is most likely IgM but the antiglobulin reagent does not detect IgM. Polyspecific detects IgG and C3d only.
A patient who has not been transfused within the past three months has the pollowing pre-transfusion results:
ABO/Rh: O Positive
The antibody screen was positive, and so an antibody ID panel was tested, and the results are below.
Cell AGT CC
1 2+ NT
2 2+ NT
3 2+ NT
4 2+ NT
5 2+ NT
6 2+ NT
7 2+ NT
8 2+ NT
9 2+ NT
10 2+ NT
11 2+ NT
Auto 2+ NT
Which choice below is the BEST step (that will give you new and helpful information) to perform next?
a. DAT
b. Elution
c. Autoadsorption
d. Test cells that are negative for high frequency antigens
c. Autoadsorption
This patient most likely has a broad spectrum autoantibody in the serum based on the results given. When selected the BEST step to perform next, you would select a test that will give you the most new and helpful information.
If you perform a DAT, it is likely it will be positive but what does that really tell you that is new? We already know the autocontrol is positive and the positive DAT is expected in this case.
If you perform an elution next, the likely result is that all cells will be positive in the panel. Again, what does that really tell you? If we are seeing a broad spectrum autoantibody in the serum, then it is likely that it is also in the eluate. Especially if you are low on sample and have to choose between an eluate or autoadsorption, the adsoprtion will be the most beneficial. If there is enough sample, an elution still be done to help confirm the WAA, but wont help transfusing the patient and determining if there’s an alloantibody present.
Testing the serum against selected cells that are negative for high frequency antigens won’t help much at this point since the autoantibody will likely react positive with all cells tested. The patient has not recetly been transfused so a HTR to a high incidence antibody is not suspected.
Therefore sicne the patient has not been recently transfused, we could do an autoadsorption procedure, This would remoev the autoantibody and leave behind any alloantibodies. It is important that we know if any clinically significant alloantibodies are present. Dong an autoadsoprtion will give us the “most bang for the buck”.
If a patient is found to have a broad spectrum cold autoantibody, which of the following techniques below would be helpful in diminishing the effects from the cold auto within the testing system?
a. pre-warmed techniques
b. use of anti-IgG monospecific AHG reagent
c. cold adsorption (all or auto)
d. all of the above would be helpful
d. all of the above would be helpful
Cold reacting autoantibodies can be a nuisance in the blood bank. They can interfere iwht testing and make detection of clinically significant alloantibodies more difficult. All of the procedures listed can be used to reduce the likelihood of detecting the cool autoantibody.
A patient is on high levels of penicillin delivered via an IV line. He has strongly positive DAT. The serum antibody screen shows negative reactions with SCI, SCII, and SCIII. The autocontrol is positive at AGT phase. The citric acid elution is negative when tested with screen cells and ABO reverse cells. What additional cells could be tested with the serum and eluate in an attempt to identify the cause of the positive DAT?
a. cord cells
b. Rh null cells
c. Drug coated cells
d. Panel of cells positive for low frequency antigens
c. Drug coated cells
In this vase the patient has been on a large doses of IV pnicillin which should always bring to mind the possibility of DIIHA. High dose penicillin can cause the patient to make antibodies to the drug itself. The high levels of drug coat the patient cells with drug haptens. The anti-drug antibody binds to the drug which is attached to the patient’s RBCs causing the RBCs to be coating with antibody and drug. (See Tech Man figure 20-2 for schematic)
Testing the patient serum and eluate with drug coated cells can help ID this anti0Drug antibody. The antibody is directed against the specific drug, not RBC components. Therefore, the specific drug must be present in the test system. IV penicillin in large doses is a classic example of this anti-drug mehanism.
Anti-ceftriaxone antibodies are known to cause intravascular hemolysis via which drug-anti-drug mechanism?
a. Drug hapten
b. Membrane modification
c. Immune complex
d. Warm autoantibody production
b. Membrane modification
A patient has been on large doses of alpha-methyldopa (trade name Aldomet) for a extende period of time. The patient presents with the following pre-transfusion testing results:
ABO = B Pos
SCI = 2+
SCII = 2+
SCIII = 2+
Autocontrol = 2+
Hemoglobin = 7.0
This scenario represents a drug induced hemolytic anemia due to which mechanism?
a. Drug hapten
b. Membrane modification
c. Immune complex
d. Warm autoantibody production
d. Warm autoantibody production
Alpha Methyldopa is a classic cause of warm autoantibody production. Although the exact mechanism has not been proven, it has been postulated that the drug alters the T-suppressor cells which in turn allows the body to produce antibody against itself. Unlike the other drug mechanisms, once the warm autoantibody is produced it will react with all cells tested, not just those coated with drugs.
A patient has a compensated hemolytic anemia due to cephalosporin, acting according to the membrane modification system. This patient’s DAT results are below:
Poly = 2+
IgG = 2+
C3 = 2+
Control = 0
An eluate is performed and tested against panel cells, ABO reverse cells and cephalospprin coated cells. What is the most likely pattern of reactivity that we will see with the eluate?
a. All cells react 2+
b. Panel is negative. Reverse cells are negative. Drug coated cells are positive.
c. Panel is positive. Reverse cells are negative. Drug coated cells are positive.
d. All cells are negative.
d. All cells are negative.
In membrane modification, proteins non-specificity adhere to the RBCc membrane. The RBC membrane is modified by the drug and acts like a magnet to randomly attach protein molecules. There is no antibody production that occurs. Therefore, the elaute will be negative with all cells tested as well as reagent cells where the membrane has not been modified.
