Transcript Hemolytic Disease of the Newborn, Current Methods of Diagnosis

Unit 11 Neonatal and
Obstetrical Transfusion
Practice – Part 2
Terry Kotrla, MS, MT(ASCP)BB
Laboratory Investigation During
Neonatal Period
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Sample of cord blood obtained.
Avoid contamination with Wharton’s jelly.
Wharton’s jelly is a gelatinous substance
which protects umbilical cord.
If it contaminates blood it will coat cells and
cause false positive in forward type.
If false positive obtained wash thoroughly and
repeat test.
Laboratory Investigation During
Neonatal Period
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Tube is labeled in delivery room with MOTHER’S
information.
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Labeled as “Cord Blood”
Her name
Her ID number
Date and time of collection which is the birth.
Kept in blood bank for 7 days.
Laboratory Investigation During
Neonatal Period
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Antepartum, postpartum testing on mother.
ABO, D and antibody screen on mother.
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During first prenatal visit.
At hospital during delivery
If screen positive,identify alloantibodies.
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Determine clinical significance of alloantibodies
and notify physician if significant.
If significant, follow with titers during pregnancy
Laboratory Investigation During
Neonatal Period
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Cord blood
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Determine ABO/D if indicated
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Some hospitals perform ABO/D on cordbloods of all
group O mothers, if baby A or B then DAT is done.
All cord bloods from D negative mothers must be
typed, if D positive mother must receive RhIg
False positive may occur (types as AB pos with
pos D control) due to Wharton’s jelly, repeat on
thoroughly washed rbc sample.
Laboratory Investigation During
Neonatal Period
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Cord blood
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May get false negative with anti-D when mother
has immune anti-D and baby is D positive.
Every D antigen site on the baby’s rbcs gets
coated with maternal anti-D leaving no sites
available for reagent anti-D to attach.
Weak D test and D control will be STRONGLY
POSITIVE as the immune anti-D is IgG and will
react with AHG.
Laboratory Investigation During
Neonatal Period
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Cord blood DAT
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Some hospitals perform DAT on all cord bloods.
Others will perform only if necessary,
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mom has clinically significant immune antibody.
group O mother has A or B baby.
Immune antibodies cause strongly positive DATs
if infant is antigen positive.
ABO is very, very weak.
Laboratory Investigation During
Neonatal Period
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Positive DAT and cord blood elutions
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Rarely performed any more.
If mom is group O with negative antibody screen
and baby is A or B comment “positive DAT
probably due to maternal ABO antibodies”.
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It is possible to elute immune anti-A, -B or –A,B off
any ABO incompatible baby regardless of results of
DAT.
Immune antibodies elution usually performed.
Laboratory Diagnosis of ABO HDFN
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HDFN caused by ABO incompatibility is
clinically mild, with jaundice most
frequently developing within 24 hours of
birth.
Laboratory Diagnosis of ABO HDFN
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Profile - MEMORIZE
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T&S on mom – Mom group O, screen neg
DAT on cord cells, weakly positive
ABO/D type on cord cells is A or B
Elution testing on cord cells – anti-A or –B &A,B eluted.
Bilirubin on infant – 12 mg/dL or more
Transcutaneous Monitoring
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Transcutaneous bilirubinometry screening tool for jaundice in
well, full-term babies.
If elevated blood test will be ordered.
Leads to approximate 50% decrease in blood testing.
Laboratory Diagnosis of ABO HDFN
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Profile - MEMORIZE
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H&H on infant – decreased.
Infant peripheral smear – hypochromia,
polychromasia, NRBCs and microspherocytosis.
Reticulocyte count on infant – increased.
Treatment of ABO HDFN
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Except in the extremely rare cases of severe
HDFN produced by ABO incompatibility,
phototherapy with UV light is the usual
treatment.
UV light converts bilirubin into nontoxic
isomer photobilirubin, transported to liver.
Photobilirubin rapidly excreted in the form of
bile.
Phototherapy – Light Therapy
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Isolette with UV lights
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Therapy uses blue light (420-470 nm) that converts bilirubin so it can be
excreted in the urine and feces.
Blinders protect baby’s eyes from damage that may lead to retinopathy
Usually do not wear diaper.
Can be done at home.
Phototherapy – Bili Blanket
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Much more humane.
Lightweight, fiberoptic pad delivers up to 45 microwatts of
therapeutic light for treatment of jaundice while allowing
infant to be swaddled, held and cared for by parents and
hospital staff.
Compact unit can be used for hospital and homecare.
Bilirubin Degradation by Phototherapy
Treatment of ABO HDFN
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The need for exchange transfusion is RARE.
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Risk of mistake being made and giving baby their
own A or B type, triggers more hemolysis.
Blood for exchange must be:
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Compatible with baby AND mother.
D compatible with infant.
“Other” Hemolytic Disease
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Uncommon, occurs in ~0.8% of pregnant women.
Immune alloantibodies usually due to anti-E, -c, Kell, -Kidd or -Duffy.
Anti-K
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disease ranges from mild to severe
over half of the cases are caused by multiple blood
transfusions
is the second most common form of severe HDN
Anti-M very rare
Laboratory Diagnosis of Other HDFN
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Profile - MEMORIZE
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T&S on mom – antibody screen is POSITIVE
Immune antibody identified.
DAT on cord cells is positive, strength varies.
Elution testing on cord cells
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Test eluate against panel, specificity of antibody should be same
as maternal antibody.
If ABO incompatible test A and B cells as well.
Bilirubin is determined and evaluated.
CBC and reticulocyte determined and evaluated.
Treatment of Other HDFN
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May be diagnosed prenatally.
Depending on antigen strength on baby’s cells
and other variables disease ranges from mild
to severe.
MOST cases require phototherapy.
RARELY exchange transfusion necessary.
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Blood must be compatible with baby & mother.
Lack all antigens to which she has antibodies.
Rh (anti-D) Hemolytic Disease
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Early 1930’s classic observations of
kernicterus, hydrops fetalis and anemia
termed erythroblasosis fetalis.
1938 suggested the cause was transfer of
immune antibodies, incorrectly assumed fetal
hemoglobin was target.
With discovery of D antigen led researchers to
correctly identify the cause.
Immunization to D Antigen
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Immunization to D depends on dose of D pos
rbcs and ability to respond to the antigen.
One third of individuals are non-responders.
Two types of responders
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Differ in terms of type and quantity of anti-D.
Hyperresponders produce extremely high titers of
both IgM and IgG anti-D
Immunization to D Antigen
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Caused by exposure to D pos rbcs through
transfusion or pregnancy with D pos fetus.
Subsequent exposure, such as pregnancy with
D pos fetus, elicits secondary immune
response.
Characterized by ↑ titers of IgG anti-D.
Immunization to D Antigen
Immunization to D Antigen
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Was noted in 1943 that ABO incompatibility
between mother and fetus reduced chance of
immunization to D.
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Maternal ABO antibodies present naturally.
Cause destruction of A or B cells before her
immune system has chance to recognize D
antigen as foreign.
Anti-D (Rh) HDFN
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If the current pregnancy is the immunizing
event seldom clinical signs of HDFN.
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Primary immune response – IgM
If progression to IgG DAT will be positive.
Antibody titer not high enough to cause severe
hemolysis.
If this is first pregnancy and HDFN is severe
MUST have had previous exposure.
Anti-D (Rh) HDFN
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Maternal IgG anti-D destroy fetal D positive red blood cells
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Baby's responds to hemolysis by trying to make more red blood cells very quickly
in the bone marrow and the liver and spleen.
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Results in anemia.
Anemia limits the ability of blood to carry oxygen to baby's organs and tissues.
Organs enlarge - hepatosplenomegaly.
New red blood cells released prematurely from bone marrow and are unable to do the
work of mature red blood cells.
As the red blood cells break down, bilirubin is formed.
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Babies unable to get rid of the bilirubin.
Builds up in the blood (hyperbilirubinemia ) and other tissues and fluids of the baby's
body resulting in jaundice.
The placenta helps get rid of some of the bilirubin, but not all.
Prenatal Diagnosis of Anti-D HDFN
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Detectable antibody titer rarely observed before 28
weeks if THIS is the immunizing event.
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Usually detectable at 35th week or later.
Titer low.
Subsequent pregnancy with D pos fetus
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Anti-D titer of 16 or ↑ with previous affected child or 64
without history indicates affected fetus.
Amniocentesis performed at 24-28 weeks OR 6-8 weeks
prior to previous fetal loss to assess fetal status.
Complications During Pregnancy
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Severe anemia with enlargement of the liver and spleen
When these organs and the bone marrow cannot compensate
for the fast destruction of red blood cells, severe anemia
results and other organs are affected.
Hydrops Fetalis
This occurs as the baby's organs are unable to handle the
anemia. The heart begins to fail and large amounts of fluid
build up in the baby's tissues and organs. A fetus with
hydrops is at great risk of being stillborn.
Hydrops Fetalis
Anti-D (Rh) Clinical Presentation
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Varies from mild jaundice and anemia to hydrops fetalis (with ascites, pleural and
pericardial effusions)
Chief risk to the fetus is anemia.
Extramedullary hematopoiesis due to anemia results in hepatosplenomegaly.
Risks during labor and delivery include:
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asphyxia and splenic rupture.
Postnatal problems include:
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Asphyxia
Pulmonary hypertension
Pallor (due to anemia)
Edema (hydrops, due to low serum albumin)
Respiratory distress
Coagulopathies (↓ platelets & clotting factors)
Jaundice
Kernicterus (from hyperbilirubinemia)
Hypoglycemia (due to hyperinsulinemnia from islet cell hyperplasia)
Infant Laboratory Findings
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Mom - T&S will reveal positive antibody screen.
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Anti-D is the commonest form of severe HDN. The disease varies from mild
to severe.
May have additional Rh antibodies present, i.e., anti-C or anti-E.
Infant - Vary with severity of HDN and include:
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Anemia
Hyperbilirubinemia
Reticulocytosis (6 to 40%)
↑ nucleated RBC count (>10/100 WBCs)
Thrombocytopenia
Leukopenia
Positive Direct Antiglobulin Test
Hypoalbuminemia
D negative blood type
Smear: polychromasia, anisocytosis, no spherocytes
Blood Smear
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Polychromasia
Anisocytosis
Increase NRBCs
no spherocytes
End of Unit 11- Part 2