Blood bank exam 4 review session

What is the cause of HDFN?

Typically an IgG antibody from mom crosses the placenta and has contact with fetal cells

What is the source of fetal antigens that mom may have antibodies against?

The baby's father

ABO incompatibility generally occurs in a group __ mother with a group __ baby.

O; A or B

ABO incompatibility is an issue in the first pregnancy, or in sequential pregnancies?

First pregnancy

Rh incompatibility is an issue in the first pregnancy, or in sequential pregnancies?

Sequential pregnancies

When doing Rhogam studies, what tests are performed on the cord sample?

ABO/Rh (only the front type)

Weak D if baby is Rh neg

DAT (only IgG)

When doing Rhogam studies, what tests are performed on the mom's sample?

ABO/Rh

Fetal screen if indicated by baby's sample

If mom and baby are both Rh neg (and baby is weak D neg), is Rhogam indicated?

No

If mom is Rh neg and baby is Rh pos or weak D pos, what is the next step?

Perform a fetal bleed screen

If a fetal bleed screen is negative, what is the next step?

Administer one dose of Rhogam to mom

If a fetal bleed screen is positive, what is the next step?

Perform weak D testing on mom. Then perform quantitative testing (such as KB) to determine the appropriate dose of Rhogam.

If mom is Rh neg and baby is Rh undetermined, what is the next step?

Quantitative testing

What do you suspect if a fetal bleed screen result is strongly positive?

Large bleed, or technical error (accidentally using cord cells)

How much blood does one dose of Rhogam cover?

30 mL

How do you calculate a Rhogam dose for a 5% bleed?

0.05 * 5000 mL = 250 mL

250 mL/30 mL = 8 + 1 = 9 doses of RhIg

When should Rhogam be administered?

within 72 hours after delivery

In Rhogam studies, if you have no sample from the baby, how do you proceed?

Assume the baby is Rh positive.

When is Rhogam routinely given?

For Rh neg moms, Rhogam is given at 28 weeks gestation, regardless of the baby's blood type.

What will the antibody screen look like for a mom who has been given Rhogam?

The screen will be positive, and it will look like an anti-D

What are the requirements for blood used for an intrauterine transfusion?

Washed

Higher hct

Fresh as possible

Irradiated

Leukocyte reduced

CMV neg

Hgb S negative

O neg blood

Antigen negative

Compatible with mom

How is a fetus's blood type determined?

Percutaneous sample

Amniocentesis

Chorionic villus

What are titers used for?

Monitor HDFN

Characterize HTLAs

What titer values are considered clinically significant?

Two blank tubes difference between the previous titer and the current titer

What is a short cold used for?

ABO discrepancy

What is a eluate used for?

positive DAT IgG

What are enzymes and chemicals used for?

enhance/destroy antigens (Anti-Fya, M or N) in order to do more rule outs, such as when there are multiple antibodies, antibodies to high frequency antigens, and sometimes ABO discrepancy.

What is neutralization used for?

used to confirm an antibody, Binds antibody with soluble antigen so that a clinically significant antibody underlying can be detected.

What is prewarm technique used for?

Remove a cold-reacting antibody interference to reveal a warm-reacting allo or auto antibody

What is a cold or warm adsorption used for?

auto antibodies

What is saline replacement used for?

Rouleaux

What do you run a titer against?

A cell that is homozygous for the antigen for which the patient has an antibody. A homozygous cell has more antigen sites for the antigen of interest than a heterozygous cell.

For example, the patient has anti-Jka. Run the titer against a cell that is homozygous for Jka.

What cells are ran in a short cold?

A1, A2, B, SC I, SC II, cord cells, auto control

What is the purpose of the SC I and SC II cells ran in a short cold?

Looking for allo antibodies

What is the purpose of the cord cells ran in a short cold?

Looking for big I or little i

What is the purpose of the auto control cells ran in a short cold?

Looking for auto antibodies

What are some reasons that a patient might have an ABO discrepancy?

• cancer: down regulation of back type

• transfusion: mixed field

• age: very old and very young- no back type

• bone marrow tx: different blood type being made

• Acquired B antigen: perforated bowel

• Preanalytical errors: misidentification of patient

• Cold autoantibody

• Rouleaux

• Cell suspension is too concentrated

• Wharton's jelly: cord cells (wash to remove)

• A subgroups: do the back type with A2 cells

• Cold allo-antibodies

What blood group antigens are enhanced by enzymes?

Kidd, Rh (C,c, E,e), Lewis, I/i, P1

What blood group antigens are destroyed by enzymes?

Duffy, M, N, sometimes S

What is the sequence of steps if the antibody screen is positive?

Positive ABSC --> ABID --> phenotype patient --> phenotype donor --> crossmatch AHG

Why might you perform a DAT?

Cord cells

Positive auto control

Included with AHG XM

What are significant IgM blood group antibodies?

ABO, M, N

What are significant IgG blood group antibodies?

Kell, Kidd, Duffy

What does ficin do?

Destroys Duffy, M, N, (S)

Reduces sialic acid

Reduces zeta potential

What does AET do?

Destroys Kell, Le, Lw

What does ZZAP do?

Destroys Kell, Lu, Duffy, M, N, S

Enhances Rh, Kidd, Lewis

What does chloroquin do?

Removes bound IgG to make cell DAT negative

What does DTT do?

Destroys disulfide bonds

Destroys Kell, Lu, Lw

What does 2-ME do?

Destroys Kell, Lu, Lw

Unexpected reactions in either the forward, reverse or both in ABO typing are caused by what types of errors

• Misidentification of the patient (pre-analytical)
• Technical (analytical)
• Tech
• Reagents
• Equipment
• Incorrect entry (post-analytical)

First step in solving ABO discrepancyis to

repeat testing

What is the most likely cause of the discrepancy below?

From a healthy 25-year-old donor.

A sub group

•What is the most likely cause of the discrepancy below?

A2 subgroup with an Anti-A1

•What is the most likely cause of the discrepancy below?

Cold autoantibodies

patient has an Anti-M , what is the most likely cause of the discrepancy below? What would fix it?

Interference in the back type from the cold reacting Anti-M. Fix with A cell and B cell negative for M antigen.

What is the most likely cause of the discrepancy below? What part of the body do you think of when you have this type of discrepancy?

Acquired B – rectum or colon

What antibodies are clinically significant for causing HDFN? Which one is most common?

•Most common Anti-D

• Anti-D, Anti-C, Anti-c, Anti-E, Anti-e, Anti-K, Anti Jka, Anti-Jkb, Anti-Fya, Anti-Fyb, Anti-S, Anti-s

How do we monitor prenatal antibody activity?

Titer

Rh Immune Globulin (RhIg) is given to who?

Rh negative pregnant women

How can we test blood type of a fetus in utero?

Blood draw from amniocentesis

When selecting blood for an intrauterine transfusion, what attributes should it have?

•O neg,  Antigen negative for moms antibodies, CMV neg, irradiated, fresh , <5 days, Hgb S neg

Fetal bleed screens are done on Rh ____ moms who give birth to Rh _____ babies.

negative; positive

What is a fetal screen (rosette test)?

•A test that screens for fetal cells in moms circulation. Anti D reagent in kit attaches to Rh positive fetal cells, once incubated and washed indicator cells are added to show agglutination of fetal  cells in moms blood. They look like rosettes.

What test is a follow up for a positive fetal bleed screen?

Kleihauer Betke or Fetal Flow

Which antibody is stronger a passive Anti-D from RhIg administration or a real Anti-D?

Real Anti-D

Is HDFN caused by ABO incompatibility clinically significant? How is it usually treated?

•Usually not clinically significant, can occur in first pregnancies. Treated with phototherapy.

Kleihauer-Betke stain results on a postpartum mother indicate that there has been a fetal maternal bleed; 1.5% of the cells counted are fetal cells. Assuming the woman has a blood volume of 5000mL, please calculate the proper RhIg dosage.

0.015 x 5000mL = 75mL  75mL/30mL = 2.5 round up to 3 and add a dose

4 vials

The results of a Kleihauer-Betke stain indicate that a fetal maternal bleed of 60 mL whole blood has occurred. How many vials of RhIg is required?

60 mL/2000 mL = 0.03 x 5000 mL = 150 mL/30mL = 5  and add a dose

6 vials

Cold panel

Enhance cold reactive antibody

elution

Strip bound IgG of RBCs for ID of its specificity

What indicates the endpoint of a titer?

•The last 1+ reaction.

What is the purpose of the A1 and A2 cells ran in a short cold?

Looking for A sub

What is the purpose of the B cells ran in a short cold?

Looking for allo antibodies

What antibodies are most common?

Anti-D, Anti-E, Anti-K

Which antibodies are not clinically significant?

Anti-M, Anti-N, Anti-Lea, Anti-Leb, Anti-Lua, Anti-P1

Who is most likely to have an Anti-U? Is it clinically significant

Black population, yes it is clinically significant

What antibodies are enhanced by cold?

•Anti-M, Anti-N, Anti-Lea, Anti-Leb, Anti-Lua, Anti-P1

What population is likely to develop a Lewis antibody?

•Pregnant

Fill in the following table for the relationship between Lewis, secretor and ABO.

Genes	Antigens in Secretions	RBC phenotype
Le, Se, HH, AA	Lea, Leb, A, H
lele, Se, HH, BB		B, H, Le (a-, b-)
Le, sese, Hh	Lea
lele, sese, HH, AO	None	A, H, Le (a-, b-)
Le, sese, hh, AB		Oh, Le (a+, b-)

Genes	Antigens in Secretions	RBC phenotype
Le, Se, HH, AA	Lea, Leb, A, H	A, H, Le(a-, b+)
lele, Se, HH, BB	B, H	B, H, Le (a-, b-)
Le, sese, Hh	Lea	H, Le (a+, b-)
lele, sese, HH, AO	None	A, H, Le (a-, b-)
Le, sese, hh, AB	Lea	Oh, Le (a+, b-)

Blood group antigen	Neutralizing agent
P1
Lewis
Sda
Chido Rogers (Ch/Rg)

Blood group antigen	Neutralizing agent
P1	Pigeon egg whites
Lewis	Saliva
Sda	Urine
Chido Rogers (Ch/Rg)	Plasma

Using Rh antigen frequencies for Weiner phenotypes (Table 7-5 pg. 155 in the text). What would be the most common Weiner type for the following races?

white:

Black:

Asian

White: R₁r

Black: R₀r

Asian: R₁R₂

After you've done a panel, performed your ruling out process, and identified what antibody most likely present in a patient sample, what test should you generally do on the patient's RBC?

•Phenotyping