Blood Bank Exam Ii

Front 1

List each step and its purpose in the DAT procedure.

Back 1

1. Add one or two drops of the patient's 3-5% cell suspension: This ensures the optimum concentration of RBCs for hemagglutination assays.

2. Wash 3-4 times with saline: To remove any serum proteins and antibodies that are NOT bound to the RBC.

3. Add two drops AHG reagent: To promote agglutination by cross-linking cell bound antibody or complement .

4. Centrifuge for 15-20 secs: To promote agglutination by increasing the rate of collision between antibody bound RBCs and the AHG.

5. Re-suspend cell button, look for agglutination and grade reaction.: To detect any reaction between the RBCs and the AHG reagent. This is the visual endpoint. If agglutination is observed, it means the patient's RBCs were coated with antibody or complement in vivo (in the body).

6. Incubate at room temp (RT) for 5-10 minutes, Spin and Read The anticomplement component of the AHG reagent may require additional incubation to detect weak positives.

7. To tests with negative results, add one drop of Coombs control cells and centrifuge for 15-20 secs. ALL test should agglutinate at this time. -Coombs Control Cells are RBCs that are coated with human IgG. In a DAT with a negative result, the AHG reagent should be free floating because it did not bind to the RBCs. In that case, the free AHG should be available to agglutinate the Coombs Control Cells. If the Coombs Control Cells are agglutinated, we can assume that the AHG was added to the test system and that it is working. If no agglutination occurs, we know that the AHG reagent is not working (it may have been omitted or neutralized) and our result may be a false negative. The test must be repeated.

Front 2

List each step and its purpose in the IAT procedure.

Back 2

1. Add one drop of reagent RBCs + Two drops patient serum : To detect RBC antibodies in the patient's serum by allowing them to bind to antigens on the RBC.

2. Add Enhancement Media (optional): To promote agglutination either by increasing the rate at which antibody binds to antigen (LISS) or by creating test conditions that allow IgG antibodies to cause agglutination (albumin).

3. Incubate at 37C for appropriate time (depends on enhancement media): To allow time for the antibody to bind to the RBC antigen. 37oC is used because the only antibodies of interest are those active at or near body temperature. Antibodies that are not active near body temperature are not significant to transfusion.
(From here, the procedure is the same as the DAT)

Front 3

Will improper washing lead to false positive or false negative test results? Explain.

Back 3

False negative results: Inadequate washing fails to remove the unbound antibody. When the AHG reagent is added, it will bind to the unbound antibodies and will therefore not be available to promote agglutination of antibody coated RBCs. In this case, we say the AHG was neutralized by the unbound antibody.

Front 4

What are the components of polyspecific and monospecific antihuman globulin reagents?

Back 4

Polyspecific : Must contain at least anti-IgG and anti-C3d. It may contain other antihuman globulins like anti-IgA or anti-C3b.

Monospecific: Contains anti-human globulin to only one of the immunoglobulins. For example, anti-IgG can only have antibody to the IgG molecule.

Front 5

A physician suspects that a patient has hemolytic anemia due to a RBC autoantibody. Would you recommend a DAT or an IAT test to determine if the physician is correct? Why?

Back 5

A DAT: If the patient has an autoantibody to his own RBCs, the antibody would bind to the RBCs in vivo (in the body). The purpose of a DAT is to detect in vivo sensitization of RBCs.

Front 6

A new technician reports the following findings when performing a DAT:
Pt cells + AHG = negative ( no agglutination )
After addition of Coombs control cells = negative ( no agglutination)
What is the most likely cause for these results?
What would you suggest the new technician do?

Back 6

The most likely cause is neutralization of the AHG reagent due to inadequate washing. You should insist that the new technician repeat the test from the beginning and review some of the important points of washing. These include:
washing 3 to 4 times prior to the addition of AHG completely re-suspending the cells between each wash filling the tubes at least 2/3 full with saline for each wash completely decanting residual saline after the last wash to prevent dilution of the AHG reagent.

Front 7

Your lab has run out of Coombs control cells and your supervisor would like you to make some. How could you do this using reagents commonly available in the blood bank?

Back 7

Coombs Control cells are human RBCs coated with human IgG antibody. The simplest way to make them is by combining Group O Rh positive RBCs with a human anti-D and incubating them at 37C. Following the incubation, the cells are washed 5 to 6 times to remove any unbound anti-D and diluted to a 2-5% suspension. It is important that the anti-D used is from a human source. Monoclonal anti-D reagents will not work because they are IgM and they are mouse antibodies.

Front 8

A reagent RBC with a positive DAT is used to test a patient serum for antibody.
False + or False -
Detected by CC cells?

Back 8

False Positive The RBC is already coated with antibody before the test starts. As a result, the cell will be agglutinated by the AHG reagent regardless of what happens during the incubation period.

No- Coombs Control cells are not added to positive tests.

Front 9

A clotted sample of blood is used to perform a DAT.
False + or False -
Detected by CC cells?

Back 9

Possible False Positive Due to in vitro (in the test tube) activation of complement. In vitro activation of complement can be prevented by using anticoagulated samples (i.e. EDTA).

No- Coombs Control Cells are not added to tests with positive results.

Front 10

The patient's cells are washed once prior to the addition of AHG in a DAT.
False + or False -
Detected by CC cells?

Back 10

False Negative The unbound antibodies would not be removed and the AHG reagent would bind to the unbound antibody. As a result, the AHG would be used up and would not be available to promote agglutination of any antibody coated RBCs.

Yes- The AHG would also be unavailable to bind to the Coombs Control Cells.

Front 11

A IAT is centrifuged for 1 minute after the addition of AHG.
False + or False -
Detected by CC cells?

Back 11

Most likely a False Negative The cells would be so tightly bound to the bottom that vigorous shaking would be required to re-suspend them. This may also break apart agglutination reactions.

No- Coombs Control Cells only detect errors concerning the AHG reagent. The AHG is fine in this case.

Front 12

The AHG was not added to a DAT.
False + or False -
Detected by CC cells

Back 12

False Negative No agglutination can occur if the AHG is omitted.

Yes- When the Coombs Control Cells are added, they will not agglutinate because they require AHG to cross-link them.

Front 13

One drop of the enhancement media is added to an IAT instead of two.
False + or False -
Detected by CC cells?

Back 13

False Negative The use of an enhancement media usually reduces the required incubation time. By using the appropriate proportions of serum to enhancement media, we ensure that the test system is under the appropriate condition for that reduced incubation time. If the test environment is not optimal (i.e. the ionic strength is too high) the reduced incubation time will adversely effect the sensitivity of the test.

No- The AHG reagent is present and working so the Coombs Control Cells will agglutinate.

Front 14

The serum was not added to an IAT test.
False + or False -
Detected by CC cells?

Back 14

False Negative If the serum is omitted, there is no antibody to bind to the RBCs.

No- Again, the AHG reagent is present and working.

Front 15

When and where should blood samples for pre-transfusion testing be labeled?

Back 15

Right after the sample is drawn and at the bedside.

Front 16

How often must we obtain a new specimen for crossmatching when the patient has been transfused or pregnant in the last 3 months?

Back 16

Every 3 days

Front 17

For the following situations, determine if an immediate spin crossmatch, a "full" crossmatch or no crossmatch is required according to AABB standards. For each case determine what type of blood you would transfuse to the patient.

a 21 year old O Rh negative female with a negative antibody screen and no history of clinically significant RBC antibodies.

Back 17

O Rh Negative, Immediate Spin Crossmatch required.

Front 18

For the following situations, determine if an immediate spin crossmatch, a "full" crossmatch or no crossmatch is required according to AABB standards. For each case determine what type of blood you would transfuse to the patient.

a 6 year old O Rh negative male with a negative antibody screen but a history of an anti-D.

Back 18

O Rh Negative, Antiglobulin Crossmatch required

Front 19

For the following situations, determine if an immediate spin crossmatch, a "full" crossmatch or no crossmatch is required according to AABB standards. For each case determine what type of blood you would transfuse to the patient.

a 63 year old AB positive female with no history of clinically significant RBC antibodies but the antibody screen is positive. Anti-c is detected in antibody identification studies.

Back 19

AB Rh Positive units that lack the c antigen ( c- RBCs), Antiglobulin Crossmatch

Front 20

For the following situations, determine if an immediate spin crossmatch, a "full" crossmatch or no crossmatch is required according to AABB standards. For each case determine what type of blood you would transfuse to the patient.

any patient requiring only plasma products.

Back 20

ABO Compatible (minor side), no crossmatch is required.

Front 21

Why are screening cells selected to be homozygous for the C, c, E and e antigens?

Back 21

To increase the sensitivity of the antibody screen. Most antibodies show dosage and react more strongly with cells from donors that are homozygous for the corresponding antigen.

Front 22

A RBC antibody is clinically significant if it causes _______________ or __________________ .

Back 22

Lysis or phagocytosis of antigen positive RBCs.

Front 23

Will the antibody screening detect RBC antibodies directed against most low frequency RBC antigens? Why or Why not?

Back 23

NO, because the screening cells DO NOT have the corresponding antigens on their surface.

Front 24

Does a compatible crossmatch guarantee the normal survival of the transfused RBCs? Why or Why not?

Back 24

No, because :
a.The crossmatch can NOT detect very low levels of antibody, so the patient can have a secondary immune response.

b.A compatible crossmatch does NOT prevent primary immunization to antigens found on the transfused RBCs.

Front 25

Can a patient have a negative antibody screen and incompatible crossmatches? Defend your answer.

Back 25

Yes, if the patient has an antibody to an antigen NOT found on the screening cells but present on the donor cells. This usually indicates an antibody to an antigen found in less than 2% of the population. In addition, if the donor unit has a +DAT, it will be incompatible even if the patient does NOT have an antibody to it.

Front 26

Jane Doe, a 30 years old female, is the victim of an auto accident. She is admitted to the ER and is in need of immediate transfusion.

The physician calls to say the patient needs blood now and can not wait for pre-transfusion testing to be performed. What should the technologist/technician in the blood blank do? Why?

Back 26

Issue uncrossmatched RBCs. The attending physician must determine if the need for immediate transfusion out weighs the risk of eliminating pretransfusion testing. Most blood banks have the physician sign a form indicating they realize that no pre-transfusion testing was performed.

Front 27

Jane Doe, a 30 years old female, is the victim of an auto accident. She is admitted to the ER and is in need of immediate transfusion.

If uncrossmatched blood is sent, what ABO and Rh type is appropriate?

Back 27

O Rh negative, this is a woman in child bearing years, do NOT use Rh positive.

Front 28

Jane Doe, a 30 years old female, is the victim of an auto accident. She is admitted to the ER and is in need of immediate transfusion.

Is there any special labeling required for uncrossmatched blood? If so, what is it?

Back 28

The label must clearly state that it is uncrossmatched.

Front 29

Jane Doe, a 30 years old female, is the victim of an auto accident. She is admitted to the ER and is in need of immediate transfusion.

The blood bank technologist checks the history files and finds that this patient was in the hospital 3 months ago and is an A Rh positive. What type of blood should be sent the ER now?

Back 29

O Rh negative. Previous records can NOT be used to determine appropriate blood for transfusion.

Front 30

Jane Doe, a 30 years old female, is the victim of an auto accident. She is admitted to the ER and is in need of immediate transfusion.

We finally receive a patient blood sample. A nurse brings it to the Transfusion Service with a request for 4 more units of packed RBCs STAT! There is NO label on the tube. The nurse assures the technologist that the sample is from the patient and should use it for compatibility testing. The nurse offers to write the patient's name on the tube and says the patient will surely die if we do not use this sample. What should be done? Why?

Back 30

The technologist/technician should calmly take the sample from the nurse and then tell them that a new properly labeled sample must be obtained. Tell the nurse that the blood bank will continue to supply O Rh negative uncrossmatched units until a properly labeled sample is obtained. The technologist/technician should remain calm and helpful but firm about this point. Misidentified patients and samples are by far the most common way that patients receive ABO incompatible transfusions.

Front 31

List the minimum information required by AABB Standards to positively identify a patient at the time of blood collection.

Back 31

Last name, first name, and a unique identification number.

Front 32

Why will a donor unit with a positive DAT result in an incompatible crossmatch? Would you transfuse a unit with a positive DAT? Why or why not?

Back 32

A positive DAT indicates that the donor RBCs were coated with antibody or complement in the donor’s body. As a result, when these RBCs are used in a major crossmatch they will ALWAYS agglutinate when the AHG is added because they are coated with antibody before the test even started.

Do NOT transfuse these cells, because they are coated with antibody and are therefore likely to be cleared from the recipient’s circulation.

Front 33

A 20 year old non-transfused male has a positive antibody screen (both cells), a positive autocontrol and all RBC units crossmatched are incompatible. What is the most likely cause of the incompatible crossmatches?

Back 33

The patient has an autoantibody in the serum. RBC autoantibodies react with virtually all RBCs, including the antibody makers own RBCs. In this case the autologous control is positive indicating an autoantibody and the serum is reacting with all RBCs.

Front 34

Can you have a positive antibody screen and compatible crossmatches? Defend your answer.

Back 34

Yes, if the donor RBCs lack the antigen to which the patient has antibody. For example, a patient with an Anti E would have a positive antibody screen but only 3 out of 10 donor units would be E positive. (70% of donors would be compatible.).

Front 35

Is the Kell antigen slightly or very immunogenic?

Back 35

Very, second only to D. 5-10% of K- individuals transfused with K+ RBCs will make anti-K.

Front 36

What antigen in the Kell system is found more frequently in the African American population (in relationship to the White population)?

Back 36

Jsa about 20% in the African American Populations <1% in the white population.

Front 37

What is dosage?

Back 37

Dosage is the ability of an antibody to react more strongly with cell from homozygous individuals compared to RBCs from heterozygous individuals.

Front 38

What antibodies can the Ko phenotype make?

Back 38

All of the antibodies in the Kell system if exposed to the antigens, including Anti-Ku.

Front 39

Which antibodies are notorious for causing delayed transfusion reactions? What factors contribute to this?

Back 39

The Kidd antibodies. Their antibody titers drop off rapidly, but respond quickly to a second stimuli.

Front 40

The antigens of the Kell and Kidd system are autosomal __________________.

Back 40

Codominate

Front 41

Which blood group system is similar to the Rh system because of its close linkage?

Back 41

The Kell system

Front 42

Which antibody reacts poorly in LISS?

Back 42

Anti-Kell

Front 43

Which antibodies are very good at fixing complement?

Back 43

The Kidd antibodies

Front 44

What is the genotype of the rare Jk(a-b-) person?

Back 44

Homozygous for the silent allele Jk

Front 45

If a patient had a positive antibody screening and 9 out of 10 units crossmatched were compatible, what antibody would you most likely suspect?

Back 45

Anti-Kell

Front 46

Which RBC genotype is resistant to lysis in 2M urea?

Back 46

Jka-b-

Front 47

What are intravascular and extravascular hemolysis?

Back 47

In vivo lysis of RBCs can result from (1) the interaction of complement components with the RBC membrane (i.e., intravascular hemolysis) or (2) the removal of cells sensitized with IgG and/or complement by the reticuloendothelial system [liver and spleen; RES] (i.e., extravascular hemolysis).

Front 48

Are Duffy antigens as immunogenic as K or D?

Back 48

No, only 0.23% of Fy (a-) individuals transfused with Fy (a+) donor units will make anti-Fya. Fyb is less immunogenic that Fya.

Front 50

What is the connection between the Fy(a-b-) phenotype and malaria?

Back 50

Persons who are Fy (a-b-) are resistance to malarial infections caused by Plasmodium vivax or knowlesi. Duffy antigens are at the junction site where the parasite enters the RBCs. Fy (a-b-) individuals are resistant to infection because they lack the antigens and therefore the junction site. Keep in mind that there are other species of Plasmodium which cause malaria and can enter Fy (a-b-) RBCs.

Front 51

What is the affect of enzymes on the Fya and Fyb antigen sites?

Back 51

They are destroyed.

Front 52

Are S and s alleles of M and N?

Back 52

No. S and s are alleles. M and N are alleles. M/N and S/s are two separate loci that are linked.

Front 53

What race is the U negative phenotype associated with?

Back 53

African American- 1% are U-
Africans- 1-35% are U-

Front 54

What is the S/s phenotype of U negative people?

Back 54

U negative individuals are always S-s-. The S, s and U antigens are carried on glycophorin B. U negative individuals are missing all or most of glycophorin B.

Front 55

What is the most probable immunoglobulin class(es) of anti-M, -N, -S and -s?

Back 55

Anti-M - usually IgM but 50-80% have an IgG portion.

Anti-N - usually IgM

Anti-S and s - usually IgG

Front 56

What antigens are found on glycophorin A? glycophorin B?

Back 56

Glycophorin A - M and N antigens (and Ena)

Glycophorin B - S, s and U

Front 57

Antibodies that are active at 37C are usually clinically __________________ .

Back 57

Significant - meaning they will cause shortened survival of antigen positive RBCs.

Front 58

Will anti-M or anti-N activate complement?

Back 58

No

Front 59

Which antibody is enhanced by decreasing the pH of the serum or adding glucose?

Back 59

anti-M

Front 60

When a RBC is agglutinated by the lectin Vicia graminea, the RBC is positive for which antigen?

Back 60

N

Front 61

When a RBC is agglutinated by the lectin Iberis amara, the RBC is positive for which antigen?

Back 61

M

Front 62

The Se/se genes do not code for a RBC antigen, they control the expression of the _____ gene in secretions. If an individual is Se/Se or Se/se then _____ antigen will be produced in the secretory cells and the person is called a ____________ .

The se gene is an __________ and no ____ antigen will be produced in the secretor cells when an individual is se/se.

Back 62

H, H, Secretor.
amorph, H.

Front 63

Lewis antigens are produced in _____________ cells and secreted. They are not an integral part of the RBC membrane but they become RBC antigens by _______________ to the membrane.

Back 63

secretory cells, adsorption

Front 64

Se/se, ABO, Hh and Lewis genes are genetically linked or independent?

Back 64

Independent. These loci are located on different chromosomes.

Front 65

What is the difference in the frequency for Le(a-b-) in Caucasians and African American?

Back 65

The Le (a-b-) phenotype is much more common in African Americans (22%) than in the White population (6%).

Front 66

Name the antibodies that can be produced by the following Lewis types:

Le(a-b-)

Le(a+b-)

Le(a-b+)

Back 66

Le (a-b-) can produce anti-Lea and anti-Leb.

Le (a+b-) can produce anti-Leb.

Le (a-b+) can NOT produce Lewis antibodies.

Front 67

List two reasons Lewis antibodies do not cause HDN.

Back 67

The antibodies do not cross the placenta because they are usually IgM.

The antigens are not developed on newborns, all newborns type Le (a-b-).