Week 8

Question 1

What is the clinical significance of cold antibodies?

Answer 1

Cold antibodies are usually clinically insignificant and do not cause red cell destruction.

Question 2

Why are cold antibodies significant in testing?

Answer 2

They interfere with testing intended to detect significant antibodies.

Question 3

At which temperatures are cold (IgM) antibodies typically present?

Answer 3

Cold antibodies are typically present at IS (Immediate Spin), RT (Room Temperature), and sometimes at 37°C.

Question 4

What type of reactions can cold antibodies show on MTS gel cards?

Answer 4

Cold antibodies can show mixed field reactions on MTS gel cards.

Question 5

How can weak reactions of cold antibodies on a panel be enhanced?

Answer 5

By incubating the panel at or below room temperature, sometimes at 4°C in a fridge.

Question 6

What does a positive DAT indicate in the context of cold antibodies?

Answer 6

It indicates that patient cells are reacting with patient plasma in vivo.

Question 7

What is the next step if polyspecific testing is positive for cold antibodies?

Answer 7

The next step is to differentiate between IgG and C3.

Question 8

What kind of reaction strength is commonly observed across the cell panel in cold antibody testing?

Answer 8

Non-specific reactions or phases with fairly consistent reaction strengths.

Question 9

What technique might be used if cold antibodies are causing confusion in test results?

Answer 9

The absorption technique may be used to try and remove the antibody.

Question 10

How can cold antibodies lead to ABO discrepancies, and in which blood group is this not typically seen?

Answer 10

Cold antibodies can cause ABO discrepancies, but this is not typically seen in Group O patients.

Question 11

What medical conditions are often associated with patients who have cold antibodies?

Answer 11

Mild anemia, Mycoplasma pneumonia infection, or infectious mononucleosis.

Question 12

What technique might be required in crossmatching blood for patients with cold antibodies?

Answer 12

A prewarm technique may be required.

Question 13

What class of antibodies does the Ii blood group system belong to, and what is its optimal reaction phase?

Answer 13

It belongs to Class IgM, with an optimal reaction phase at room temperature.

Question 14

Where is the i antigen expressed in the Ii blood group system?

Answer 14

The i antigen is expressed on newborn cells and cord blood cells.

Question 15

Over what period does the i antigen convert to the I antigen structure in the Ii blood group system?

Answer 15

The i antigen converts to the I antigen structure over a 2-year period.

Question 16

Where is the I antigen expressed in the Ii blood group system?

Answer 16

The I antigen is expressed on adult cells.

Question 17

What type of antibody is Anti-I and when does it show optimal reactivity?

Answer 17

Anti-I is a common autoantibody with optimal reactivity at colder temperatures.

Question 18

Is Anti-I clinically significant?

Answer 18

No, Anti-I is clinically insignificant, although it can vary in reactivity with different adult red cells.

Question 19

What causes variability in reactivity of Anti-I with adult red cells?

Answer 19

The variability is due to different chain structures in the oligosaccharide chains (I antigens are branched while i antigens are linear).

Question 20

What makes Anti-I a compound antibody?

Answer 20

Anti-I also reacts with H, forming a compound antibody.

Question 21

What is Anti-IH, and with which cells does it exhibit stronger agglutination?

Answer 21

Anti-IH exhibits stronger agglutination with red cells that have a higher number of H antigens, such as O and A2 cells.

Question 22

Why can Anti-I and Anti-IH cause confusion in serological testing despite being clinically insignificant?

Answer 22

Both can interfere with testing due to their reactions, even though they are not clinically significant.

Question 23

How common are allo Anti-I and auto Anti-i antibodies?

Answer 23

Allo Anti-I is rare, and Auto Anti-i is uncommon.

Question 24

What conditions are associated with stronger Auto Anti-I?

Answer 24

Auto Anti-I is associated with Mycoplasma pneumoniae infections and cold hemagglutinin disease.

Question 25

What conditions are associated with Anti-i?

Answer 25

Anti-i is associated with infectious mononucleosis, lymphoproliferative disease, and occasionally cold hemagglutinin disease.

Question 26

What are some frequently encountered cold allo-antibodies?

Answer 26

Anti-P1, Anti-M, Anti-N, Anti-Lea, and Anti-Leb.

Question 27

What method would you use to eliminate the M and N antibodies from reacting on a panel?

Answer 27

Use enzyme treatment, as it destroys M and N antigens, thereby preventing their reaction on the panel.

Question 28

What method would you use to eliminate the P1, Lea, and Leb antibodies from reacting on a panel?

Answer 28

Prewarm technique or cold adsorption can be used to eliminate these antibodies from reacting on a panel.

Question 29

What are some frequently encountered cold auto-antibodies?

Answer 29

Anti-IH and Anti-I.

Question 30

What causes differences in antigen levels on RBCs among the subgroups of blood type A?

Answer 30

Different A genes code for varying amounts of enzyme, resulting in fewer antigens on the RBC membrane.

Question 31

What antigens are present in the A1 subgroup?

Answer 31

The A1 subgroup has both A1 and A antigens, with Anti-B in the plasma.

Question 32

What antigens are present in the A2 subgroup?

Answer 32

The A2 subgroup has only the A antigen, with Anti-A1 and Anti-B in the plasma.

Question 33

Why might the A2 subgroup show an extra reaction in reverse cells?

Answer 33

The extra reaction occurs because A1 cells are used in reagent racks, which may react with Anti-A1 in A2 subgroup plasma.

Question 34

What percentage of the Group A population belongs to the A1 subgroup?

Answer 34

Approximately 80% of the population is in the A1 subgroup.

Question 35

How is the A2 subgroup confirmed?

Answer 35

Confirmation is done by phenotyping the patient with Anti-A1 lectin.

Question 36

What is the purpose of testing with Screen Cells I and II in cold antibody screens?

Answer 36

To detect other blood group antibodies.

Question 37

What is the purpose of the Auto Control in cold antibody screens?

Answer 37

To test for allo or auto antibodies and specifically to test for Anti-IH.

Question 38

Why are Cord Cells used in cold antibody testing?

Answer 38

For testing Anti-i or Anti-I, as cord cells have very little or no I antigens on red cells.

Question 39

What is the purpose of using A1 and A2 Cells in cold antibody screens for certain patients?

Answer 39

To test for Anti-A1 and Anti-IH, particularly in patients suspected of being in group A or AB.

Question 40

Why are B Cells tested on patients suspected of being group B and AB in cold antibody panels?

Answer 40

To test for Anti-IH.

Question 41

What is the reason for using both A1 and B Cells in cold antibody panels for suspected group AB patients?

Answer 41

To test for Anti-IH.

Question 42

How can extra reactions due to a subgroup of A be confirmed?

Answer 42

By using a cold panel (only A1 cells will be positive) and phenotyping with Anti-A1 lectin. Anti-A1 lectin is derived from the plant Dolichos biflorus.

Question 43

What steps are taken to confirm other blood group antibodies in cold antibody testing?

Answer 43

Use a cold panel (Screen Cells I and/or II will be positive), perform a full panel to identify the antibody (using exclusion rules), and ensure the auto control is negative.

Question 44

What are RA/RB cells used for in the context of other blood group antibodies?

Answer 44

RA/RB cells are commercially purchased cells used for reverse testing in the ABO group; they are positive when phenotyping, reacting with the antibody in the plasma.

Question 45

How are cold auto antibodies, such as Auto Anti-I or Auto Anti-IH, confirmed?

Answer 45

By performing a cold panel (auto control is positive), DAT testing (positive with Anti-C3d), and titration to determine antibody concentration.

Question 46

Which reagent should be used in the AHG test to avoid anti-complement activity?

Answer 46

Use Anti-IgG antiglobulin reagent instead of a polyspecific reagent.

Question 47

What readings should be eliminated to avoid reactivity in antibody testing?

Answer 47

Eliminate the IS (Immediate Spin) and 37°C readings.

Question 48

What enhancement technique should be avoided, and what should be used instead?

Answer 48

Avoid the LISS enhancement technique, use albumin, and increase the incubation period.

Question 49

What technique should be performed to avoid reactivity, and what special steps are involved?

Answer 49

Perform the prewarm technique by warming all samples and reagents and using warm saline for washing. Crossmatch units with a prewarm technique to prevent incompatibility.