Download CLS 2215 Principles of Immunohematology

CLS 2215
Principles of
Immunohematology
Hemolytic Disease of
the Newborn
HDN
Hemolytic Disease of the
Newborn
• HDN occurs when the Mother has an antibody
capable of crossing the placental barrier that
is specific to an antigen present on the red
blood cells of the fetus.
• Fetal red cells become coated with the IgG
alloantibody and undergo accelerated
destruction both before and after birth.
– Where does the baby get an antigen that is foreign
to the Mom?
• It’s the Dads fault!
Mechanism of HDN
Immunization and Production of
Antibody
1. Fetomaternal Bleed:
2. During subsequent pregnancies:
Categories of HDN
1. Rh System
Antibodies
1.
2. Other Blood
Group Antibodies
2.
3. ABO Antibodies
3.
Pathophysiology of HDN
• Accelerated red cell destruction leads fetus to
increase production of RBCs therefore there
are increased numbers of nucleated RBCs.
Severe cases of HDN can result in:
• Generalized edema of the fetus:
• Severe anemia:
Pathophysiology of HDN
Bilirubinemia
•
•
Results from increased RBC destruction
Fetus in utero:
•
Newborn:
Prenatal Testing
Patient History:
•
Which pregnancy is this?
•
Has she ever been transfused?
•
Is she Rh negative? Has she had antenatal
RhIg?
•
Does she have a previously identified
unexpected antibody?
Prenatal Testing
Test Mom for ABO, Rh (Weak D), and
Antibody Screen
Group O Mom :
Rh Negative Mom:
Prenatal Testing
Positive Antibody Screen?
• Identify antibody and perform titration
if antibody is clinically significant (antiD, K, etc.). FREEZE the serum sample. If
a subsequent titer is requested you need
to compare the first titer results with
the second titer. Run both titers in
parallel and compare endpoints.
• Has the titer increased? Two tube increase is
clinically significant. May lead to more sensitive
testing to determine severity of disease.
Rh Immune Globulin
What is it?
• How does it work?
Rh Immune Globulin
• Full Dose:
• Mini dose:
When to give RhIg
Antenatal administration
Amniocentesis
When to Give RhIg
Postpartum Administration
• When Mother is Rh negative (and is negative
for anti-D) and Baby is Rh positive. It is that
simple.
• How much?
Rosette Test
• Purpose:
• Qualitative:
Rosette Test - Principle
• Add chemically modified anti-D to Mothers
washed Post Partum (EDTA) red cells and
incubate at 37oC. Anti-D will attach to Rh
Positive cells present.
• Wash cells and add R2R2 indicator cells.
Indicator cells will “rosette” around anti-D that
has attached to the Rh positive cells.
• Centrifuge and resuspend the suspension and
read microscopically looking for Rosettes.
• Rosettes present?
Kliehauer Betke (Acid Elution)
• Purpose:
• Quantitative:
Kliehauer Betke (Acid Elution)
• Principle: Draw a Post Partum EDTA sample
from the mother and make and fix a blood
smear on a glass slide. Flood the smear with
an acid solution. The Hgb of adult red cells is
washed out by the acid solution while red
cells with Hgb F are not. Counter stain
(Safranin) the smear. Cells with Hgb F stain
red while the adult red cells remain
transparent.
• Count number of stained Hgb F red cells
within 2000 adult (Hgb A) red cells.
Kliehauer Betke Stain
Calculations
• # Fetal cells / 2000 adult cells x 100 = % of
Fetal cells present in the maternal circulation.
• % of Fetal cells X 50 = number of mls of Fetal
bleed
• # of mls of fetal bleed / 30 = # vials of RhIg
required
Cord Blood Studies
Required testing on the Cord Blood of Newborn’s
with Rh Negative Moms
(suggested on Group O Moms)
• ABO group:
• Rh typing:
• Direct Antiglobulin Test:
Exchange Transfusion
• Exchange transfusion may be definitive
therapy for newborns with severe HDN.
• A process where you exchange baby red
cells with transfused red cells. Accomplishes
the following:
• Remove coated RBCs
• Remove antibody
• Lower bilirubin:
Compatibility testing for
Exchange Transfusion
• Crossmatch blood for exchange
transfusion with Mothers serum. Why?
• Can crossmatch with baby if mom is not
available, but best indication of red cell
survival is to crossmatch with the
Mothers serum. Remember the source
of the antibody is…
Which mothers are candidates for
RhIg?
• Mother Rh positive with anti-K
• Baby Rh positive with negative DAT
• Mother O negative with anti-C
• Baby A negative with positive DAT
• Mother A negative with negative IAT
• Baby O positive with negative DAT
Which mothers are candidates for
RhIg?
• Mother: A negative with anti-D, C, K
– Baby: B positive, +DAT eluate showed D, C
• Mother: A negative with negative IAT
– Baby: O positive with positive DAT, eluate neg
• Mother: AB negative with anti-D
– Baby: A negative with negative DAT