4. Exam Review

Define ABO discrepancies

unexpected rxns in forward, reverse, or both ABO typing

ABO discrepancies causes

• misidentification

• Technical: tech, reagents, equipment

• incorrect entry

If there is a discrepancy, what is the first thing you should do

repeat test

discrepancy?

A subgroup

discrepancy?

A2 subgroup with anti-A1

discrepancy?

cold auto antibody

Patient has anti-M, discrepancy?

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.

Acquired B – rectum or colon

If you see a mixed field in a patients blood type, what would you expect

That the patient has been recently transfused.

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

Within how many hours should a woman be given RhIg after delivery?

72 hrs

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

Special Techniques

What indicates the endpoint of a titer?

The last 1+ reaction.

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 (e.x ficin, trypsin)?

Duffy, M, N, S is variable

Other Blood Group characteristics

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

Lewis and Secretor genes

Antigen and neutralizing agent

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: 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

Factors affecting HDFN

• Host factors: genetic ability to produce antibodies

• immunoglobulin class (IgG)

• Antibody specificity

Out of the subclasses of IgG which are most potent

1 and 3

Outside the Rh (DCE) antibodies what other antibody is significant in HDFN

anti0K

When mom is ABO incompatible with fetus, why is detectable fetomaternal hemorrhage decreased?

Mom’s natural occurring antibodies could destroy RBCs from fetus

(ex. mom’s anti-A destroys A + RBCs)

Hydrops fetalis

edema, anemia and effusions in baby due to RBCs being destroyed so fast that spleen and liver have to help bone marrow

kernicterus

permanent brian damage due to build up of bilirubin

Monitoring HDFN

• TITERS

• ABID

• ABSC

• phenotype father

What phase are we most concerned with when performing ABSC on a mother?

AHG (IgG detection)

How to distinguish between passive and active anti-D

How to determine baby’s antigens (ABO Rh ) during pregnancy?

• amniocentesis

• chorionic villous

• mom’s plasma in 2nd trimester

Baby Hgb in womb is less than 10g/dL, a ______ _____ is performed.

intrauterine transfusion

Requirments for intrauterine transfusion

• Type O Neg

• irradiated

• CMV (-)

• less than 7 days old

• antigen neg for mom’s antibodies

• wash to get hct of 80-85%

Diagnosis of HDFN via serology

perform front type and ABSC on baby

• If (+) —→ ABSC on mom

• If (+) and mom not around—→ DAT; (+) = Eluate

Fetal Bleed Screen

performed on Rh(-) mom with Rh(+) baby

• (+)—> perform weak D on mom —(regardless of results)—> Kleihauer Betke——> give appropriate RhIg dose

Why do we perform a weak D test on mom even though we’re going to still request a Kleihauer Betke regardless of her results?

Weak D (+) = possible false (+) fetal bleed screen

Test performed post delivery

A Fetal Bleed Screen test is a _____test and if (+), it needs to be followed by a_____test such as Kleinhauer Betke or Fetal F flow to determine RhIG dosage

Qualitative; Quantitative

RhIg dosage calculation

Avg maternal blood volume is 6L

Weeks of Gestation and RhIG dose

RhIG dosage flow chart

ABO HDFN

• A/B baby and O mom

• no serological test

• phototherapy good enough (i.e. mild)

• IgG antibodies

neonatal alloimmune thrombocytopenia (NAIT)

disorder in which fetal platelets contain antigen inherited from the father and lacks in mother

• anti HPA-1

Most common ABO discrepancies occur in patients ____

plasma

First step if ABO discrepancy happpens

Repeat and pay extra attention

Guiding questions for ABO discrepancy

1. Age: old and young don’t produce anti-A/B

2. Diagnosis: ex hypogammaglobulinemia

3. Transfusion history

4. BM transplant

5. Medications: ex immunosuppressants

If mom is Rh (-) and her baby is weak D or undetermined Rh, what test is performed on mom ?

Kleinhauer Betke or Fetal F flow (FBS isn’t sensitive enough)

Sulfhydryl reagents like DTT, AET, EGA, 2-ME break _____bonds and destroy blood groups _____, _____, and ___.

disulfide;

destroy Kell, Lutheran, and LW

Enhancement medias LISS or LO-ION, PEG, and PEP enhance Ab-Ag by reducing ____ _____

zeta potential

Enzymes Papain, Trypsin, and Ficin destroy by reducing ____acid

sialic

Chloroquin removes bound IgG by breaking the ____bonds of the IgG molecules

disulfide

Most commonly performed elution method is with___

Acid

Heat (56C) and Lui Freeze Thaw are only utilized on _____

ABO

When making an eluate, why should we KEEP the last wash?

QC; to ensure that there is no unbound antibody

Cold Autoabsorption is done with _____cells or ____

autologous cells

OR

RESt (rabbit erythro stroma)

What is the Acquired B phenomenon

Type A with extra B in the front due to Bowel bacteria

*Pregnant women will most likely have an antibody against?

Lewis

Elution techniques used for

1. separating multiple antibodies

2. clarification of “compound” antibodies

3. weak antigens (Del or A subgroups)

An eluate that is panreactive is most likely a ____

WAA (warm auto antibody)