12 hdn ii
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NotesTRANSCRIPT
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HEM 2133
Immunohaematology IImmunohaematology I
Lesson 12:
Hemolytic Disease of Newborn II
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Laboratory Investigation
Cord blood from infants born to Rh-negative mothers should be tested for the D antigen
An Rh-negative woman with an Rh-positive infant should receive one full dose of RhIG infant should receive one full dose of RhIG within 72 hours of delivery, unless she is known to be alloimmunized to D already
The presence of residual anti-D from antepartum RhIG does not indicate ongoing protection
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Neonatal studies
Cord blood samples should be collected from every newborn and stored for at least 7 days in the transfusion service in the event the newborn shows signs of HDN
If HDN is suspected, both cord and maternal blood should be tested for ABO and Rh (and blood should be tested for ABO and Rh (and weak D if apparently D negative)
The maternal blood should also be tested for unexpected antibodies if the mother is D negative and the infant is D positive
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A DAT should be performed on the cord blood
RBCs and an elution performed if the DAT is
positive and the antibody identified
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Serologic Problems Seen in HDN
Cord blood should be washed several times before testing
Often, cord blood is contaminated with Whartons jelly which may cause false agglutination
(Whartons jelly - a soft connective tissue that (Whartons jelly - a soft connective tissue that occurs in the umbilical cord)
If there is doubt as to the validity of agglutination, a maternal sample should be tested for antibody or a neonatal sample should be tested for DAT and ABO/Rh
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ABO/Rh Testing
Newborns who were transfused while
intrauterine often type Rh negative or weakly
Rh positive because so much of their
circulating RBCs are of donor origin
ABO grouping also reflects the donors ABO ABO grouping also reflects the donors ABO
group and may exhibit mixed-field reaction
with ABO antisera or, if the HDN is quite
severe , may group as an O
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If the infants RBCs are heavily coated with IgG
antibodies, the Rh typing may give either
false-positive or false-negative results
The use of saline antisera or chemically The use of saline antisera or chemically
modified antisera may help in obtaining a true
Rh type
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Direct Antiglobulin Test
The strength of the DAT varies depending on:
The strength of the maternal antibody
The number of antigenic sites for the antigen to which the maternal antibody is directed
How much blood the infant has received from How much blood the infant has received from transfusions
If the maternal blood is available and a single antibody is identified, an elution from the infants RBCs is unnecessary
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If however, the maternal serum is negative for unexpected antibodies, ABO antibodies or an antibody to a low-frequency antigen must be suspected
Antiglobulin testing of the eluate from the infants cells against A1, B and O cells aids in the diagnosis of ABO HDN
Testing the eluate against paternal RBCs aids in Testing the eluate against paternal RBCs aids in diagnosing a low-frequency antibody
In addition, testing the maternal serum against the paternal RBCs confirms the presence of an antibody even when antibody screening tests and panels are negative
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Postnatal Testing Required If HDN is
Suspected
Mothers blood
ABO
Rh including weak D if D-negative
Indirect antiglobulin test (antibody screen) Indirect antiglobulin test (antibody screen)
If indirect antiglobulin test is positive, do antibody identification test
If antibody identification test is positive for IgG antibody, do hemoglobin and bilirubin on baby
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Cord blood
ABO forward only
Rh including weak D if D-negative
Direct antiglobulin test
If direct antiglobulin test is positive, do elution If direct antiglobulin test is positive, do elution
and antibody identification test on eluate
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Treatments for HDN
In utero
Intrauterine transfusion (IUT) can occur either by the intraperitoneal route or the direct intravascular approach by the umbilical vein
In intraperitoneal IUT, a needle is passed In intraperitoneal IUT, a needle is passed through the mothers abdomen and into the abdomen of the fetus
RBCs are infused into the abdominal cavity of the fetus and then absorbed into the fetal circulation
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Intrauterine Transfusion
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Selection of blood for intrauterine transfusion
Most IUT are accomplished using
Group O, Rh-negative RBCs that are less than
7 days from collection
Cytomegalovirus antibody negative or
leukoreducedleukoreduced
Gamma irradiated
Hemoglobin S negative
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Group O, Rh-negative RBCs are used because the
ABO group and Rh type of the fetus are usually
unknown
Fresh blood is usually used to provide RBCs with
the longest viability and to avoid lower pH,
decreased 2,3-diphosphoglycerate and elevated
potassium levelspotassium levels
Primary CMV infection in a fetus or newborn has
the potential for causing death
CMV antibody-negative or leukoreduced blood is
transfused to avoid this route of infection
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Gamma irradiation of cellular products is necessary to prevent graft-versus-host disease in the fetus
Hemoglobin S-negative blood is used because the decreased oxygen tension that may occur during gestation may cause hemoglobin S-containing blood to sickle
RBCs are usually dry packed to remove residual RBCs are usually dry packed to remove residual anti-A and anti-B and reconstituted with group AB fresh frozen plasma to provide coagulation factors
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Postpartum
Two consequences of HDN that may require
intervention and treatment after birth are
hyperbilirubinemia and anemia
High level of free unconjugated bilirubin are
associated with neurotoxicityassociated with neurotoxicity
Treatment modalities for hyperbilirubinemia
are phototherapy sessions or exchange
transfusions
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Phototherapy
Accelerates bilirubin metabolism through the
process of photodegradation
Effective wavelength = 420-475 nm Effective wavelength = 420-475 nm
The insoluble form of unconjugated bilirubin is
converted into a water-soluble form, which
permits more rapid excretion, without
conjugation, through the bile or urine
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Phototherapy
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Exchange transfusion
When the serum bilirubin reaches a level of 18 to
20 mg/dL in any infant with HDN, exchange
transfusion must be performed
The coated infant RBCs are removed and replaced
with RBCs with normal survival
This reduces the potential for increased bilirubin This reduces the potential for increased bilirubin
as well as reducing some of the bilirubin already
formed
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The number of unbound antibody molecules
available to attach to newly formed antigen-
positive cells is also reduced
Exchange transfusion is performed in 45 to 90
minutes by using 5 to 10 ml increments of minutes by using 5 to 10 ml increments of
blood
The increment of the infants blood is
removed first and replaced by the donor
blood in an equal volume
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Selection of blood
The RBCs used in an exchange transfusion are
from a donor whose blood type is compatible
with the mother and infants serum
It is estimated that an exchange transfusion
with a volume double that of the infants with a volume double that of the infants
blood volume replaces approximately 85% of
the infants circulating RBCs
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Because bilirubin production still may remain high, the immediate decrease in bilirubin concentration is usually only 50%
It is often followed by a rebound rise in bilirubin that may necessitate additional exchange transfusion, usually in conjunction with phototherapywith phototherapy
Furthermore, bilirubin and the offending antibody are distributed throughout the extracellular space and thus reenter the vascular space after exchange transfusion
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In addition, tissue-bound bilirubin
reequilibrates with extravascular components,
reentering the circulation and contributing to
the rebound
Premature newborn infants are more likely
than full-term infants to require exchange than full-term infants to require exchange
transfusion for elevated bilirubin because
their livers are less able to conjugate bilirubin
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Transfusions and compatibility testing
Infants with HDN , as well as many premature
infants, require ongoing transfusions to replace
blood lost through normal physiologic processes
and blood sampling for laboratory tests
The initial pretransfusion sample must be tested The initial pretransfusion sample must be tested
for ABO and Rh (and for weak D if the infant is D
negative)
The ABO needs only forward grouping because
ABO antibodies are not developed yet
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If other than group O RBCs are to be
transfused, an indirect antiglobulin test with A
and B RBCs must be performed
If residual anti-A or anti-B is present, blood of
those groups must be avoided until they are
no longer demonstrable no longer demonstrable
An antibody screen must be performed
The serum or plasma of the mother or infant
may be used for antibody screen
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Once these tests have been performed, repeat
testing for ABO and Rh may be omitted for the
remainder of the infants hospital stay
If the antibody screen is negative, If the antibody screen is negative,
crossmatching is not required for the initial or
subsequent transfusions
These procedures apply to all infants younger
than 4 months of age
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If an unexpected antibody is present, RBCs for
transfusion must lack the corresponding
antigens or be crossmatch compatible by the
antiglobulin technique until the antibody is no antiglobulin technique until the antibody is no
longer present in the infants serum