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WILLIAM'S HEMATOLOGY > 56 Alloimmune Hemolytic Disease of the Fetus and Newborn > Flashcards

56 Alloimmune Hemolytic Disease of the Fetus and Newborn Flashcards

1
Q

Manifestations of Alloimmune Hemolytic Disease of the Newborn

Disorder in which the lifespan of fetal and/or neonatal red cells is shortened as a result of binding of transplacentally transferred maternal immunoglobulin (Ig) G antibodies on fetal red blood cell (RBC) antigens foreign to the mother, inherited by the fetus from the father

A
  • Hemolytic anemia
  • Jaundice
  • Hepatosplenomegaly

in more severe cases:
* Anasarca
* Kernicterus

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2
Q

Race

Approximately 15% of ____________descent are RhD negative

A

Americans of European descent

Compared with 7% of African Americans and Hispanics, 5% of Indians, and 0.3% of Chinese individuals

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3
Q

The ________ phenotype is found in approximately 30% of RhD-“negative” individuals in East Asia and has been implicated in RhD HDFN

Phenotypes can exhibit quantitative reductions and sometimes qualitative variation in D antigen expression, potentially resulting in anti-D alloimmunization

A

DEL phenotype

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4
Q

Asymptomatic transplacental passage of fetal red cells occurs in _____% of pregnancies.

A

75%

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5
Q

The risk of sensitization increases with each trimester of pregnancy and is greatest (65%) at ________.

A

Delivery

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6
Q

The average volume of fetal blood in the maternal circulation after delivery is approximately _______ mL in most women and less than 1 mL in 96 % of women

A

0.1 mL

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7
Q

Maternal red cell antibodies fall into three classes:

A
  • Antibodies directed against the D antigen in the Rh blood group
  • Antibodies directed against the A or B antigens
  • Antibodies directed against any of the remaining red cell antigens
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8
Q

Blood group system involved in most serious cases

A

D antigen of the Rh blood group

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9
Q

In ABO hemolytic disease, the mother is usually type ___ and the fetus is either type ____

A

Type O

Type A or B

Others:
* mothers of type B and fetuses of type A
* mothers of type A and fetuses of type B

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10
Q

After anti-RhD, the following blood groups are most often involved in alloimmunization:

A
  • Rh (C, e, E, e)
  • Kell
  • Duffy
  • Kidd
  • MNS
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11
Q

Caused in large part by suppression of erythropoiesis rather than brisk hemolysis

A

Kell HDFN

  • Anti-Kell antibodies inhibit the growth of Kell-positive erythroid progenitor cells
  • Anti-Kell antibodies have also been associated with suppression of megakaryocyte and granulocyte colony-forming units, resulting in fetal and neonatal thrombocytopenia and pancytopenia

All maternal anti-Kell alloantibodies must be considered to be potentially clinically significant

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12
Q

The presence of maternal antibodies is not predictive of alloimmune hemolytic disease because

A
  • (1) they may be IgM antibodies and not traverse the placenta
  • (2) the antigens may not be present on fetal red cells or their density is very low
  • (3) the concentration of antibody in maternal blood may be very low
  • (4) the antibody Ig subclass may not interact with fetal red cells
  • (5) other mitigating factors
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13
Q

TRUE OR FALSE

ABO incompatibility is present in 15% of O group pregnancies, but hemolytic disease of the fetus or newborn occurs in about 2% of births.

A

TRUE

ABO incompatibility is present in 15% of O group pregnancies, but hemolytic disease of the fetus or newborn occurs in about 2% of births.

Rare!

Most anti-A and anti-B being IgM antibodies, which do not easily traverse the placenta.

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14
Q

TRUE OR FALSE

Fetomaternal ABO incompatibility offers some protection against primary Rh immunization because incompatible fetal RBCs are destroyed rapidly by maternal anti-A and anti-B antibodies

A

TRUE

Fetomaternal ABO incompatibility offers some protection against primary Rh immunization because incompatible fetal RBCs are destroyed rapidly by maternal anti-A and anti-B antibodies

ABO incompatibility confers no protection against the secondary immune response after sensitization has occurred

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15
Q

Type of antibody

RhD Alloimmunization:
ABO Alloimmunization:

A

RhD Alloimmunization:IgG1 and /or IgG3
ABO Alloimmunization: IgG2

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16
Q

Other features of ABO Alloimmunization

A
  • Observed higher freguency during the first pregnancy because of preexisting anti-A and anti-B in the mother (40%−50%)
  • Moderate anemia and mild hepatosplenomegaly
  • Early neonatal jaundice requiring phototherapy
  • Rarely requires exchange transfusion
  • Rarely leads to severe disease (ie, hydrops fetalis)
  • Rare incidence of late anemia
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17
Q

The hemolytic rate can be determined by using

A

Exhaled carbon monoxide end-tidal breath analyzer

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18
Q

In RhD alloimmunization, % of newborns have mild disease and do not need intervention

A

50%

  • 25%- born at term with moderate anemia and severe jaundice
  • 25% - hydrops fetalis in utero prior to the availability of intrauterine intervention
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19
Q

Associated with marked extramedullary hematopoiesis in the liver, spleen, kidneys, and
adrenal glands.

A

Hydrops fetalis

Portal and umbilical vein hypertension, hypoproteinemia (liver dysfunction), and pleural effusions and ascites can occur.

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20
Q

If severe anemia is present, infant displays pallor, tachypnea, and tachycardia; cardiovascular collapse and tissue hypoxia can occur if hemoglobin is less than

A

40 g/L

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21
Q

Timing of ABO and RhD typing and testing for unusual red cell alloantibodies during pregnancy

A

10th to 16th week

Whether RhD positive or negative, the mother should be tested again at 28 weeks’ gestation.

22
Q

If alloimmunized, the mother’s antibody titer should be determined at

A

4-week intervals from 20 to 28 weeks and every 2 weeks thereafter

23
Q

Anti-D levels and management

A
  • 4 IU/mL: referral to fetomaternal specialist for monitoring and risk assessment
  • 4 to 15 IU/mL indicates that moderate alloimmune hemolytic disease
  • Greater than 15 IU/mL: high risk of alloimmune hemolytic disease

Antibody titers are reported as the reciprocal of the highest dilution at which agglutination is observed.

A difference of two dilutions is considered significant.
If the titer becomes greater than 16 (varies from 8 to 32 in different laboratories), ultrasonography and amniocentesis can be performed to test for the bilirubin level, which predicts disease severity

24
Q

In pregnancies in which maternal sensitization occurs or there is a past history of alloimmunization, determining : __________ for all common antigens involved in alloimmune hemolytic disease may determine the risk to the fetus.

A

Paternal zygosity

  • Homozygous: assume the fetal red cells will carry that antigen
  • Heterozygous: 50% chance of carrying the antigen
25
Q

Can distinguish maternal from fetal DNA and
then amplify fetal exons that include RhD

A

Fetal DNA:
Real-time quantitative polymerase chain reaction

Accuracy of RhD phenotyping using fetal DNA is 95%.

26
Q

An indirect measure of degree of hemolysis in the fetus

A

Amniotic fluid spectrophotometry for bilirubin

Liley chart: Defines 3 zones based on ΔOD450 readings, indicating severity of fetal disease

Queenan chart: Modified Liley chart to include data from 14-40 weeks’ gestation, with 4 zones

27
Q

Replaced amniocentesis for measuring fetal anemia

A

Middle cerebral artery Doppler ultrasound measurement

  • Measuring peak blood flow, usually at 1- to 2-week intervals after week 18 until week 35, is a more accurate assessment of anemia than amniotic fluid bilirubin levels.
  • After week 38 of gestation, because of a high false-positive rate with Doppler measurements, amniocentesis and measurement of amniotic fluid OD450 are required.
28
Q

Allows direct measurement of fetal red cell antigens, blood hemoglobin, reticulocyte count, direct antiglobulin test, bilirubin level, blood gases, and lactate levels and can be done at 18 weeks’ gestation

A

PUBS (also called cordocentesis)

confirmatory

29
Q

Complications of PUBS include:

A
  • Umbilical cord bleeding
  • Chorioamnionitis
  • Fetomaternal hemorrhage and Maternal red cell sensitization
  • Fetal death (3%)
30
Q

After delivery, the cord blood of the neonate should be sampled for:

A
  • Hemoglobin
  • Bilirubin concentrations
  • ABO and Rh type
  • Direct antiglobulin test
  • Blood film
31
Q

TRUE OR FALSE

One hour after delivery, blood should be drawn from the mother to evaluate the degree of fetomaternal hemorrhage, so that an appropriate dose of anti-Rh IgG can be given.

A

TRUE

One hour after delivery, blood should be drawn from the mother to evaluate the degree of fetomaternal hemorrhage, so that an appropriate dose of anti-Rh IgG can be given.

32
Q

Erythropoiesis may be suppressed in the newborn, but marrow recovery is usually complete by __ months.

A

2 months

33
Q

Given to severely affected fetus, based on level of anemia, development of ascites, or a rising bilirubin concentration

Replaced exchange transfusion in some centers because it is a more rapid procedure

A

Intrauterine transfusion thru PUBS

O-negative, antigen-negative for any other identified antibody, cytomegalovirus-negative, irradiated packed red cells are used, cross-matched against the mother’s blood.

34
Q

Fetal hematocrit for intrauterine BT

A

≤30%

35
Q

Packed red cells are transfused to the fetus to achieve a hematocrit of

A

40% to 45%

The red cells are packed to about 75% and a calculation made as to what volume of red cells should be necessary to achieve the
desired hematocrit in the fetus.

36
Q

Intraperitoneal fetal transfusions may be necessary if:

A
  • (1) intravascular access is not possible because the umbilical vessels are too narrow in early pregnancy or
  • (2) fetal size blocks access to the cord later in pregnancy
37
Q

For a woman alloimmunized in a previous pregnancy, fetal transfusions should begin _________, but not before 18 weeks’ gestation unless hydrops is present.

A

10 weeks before the time of the earliest prior fetal death or transfusion

Transfusions are given to keep the hematocrit of the fetus in the 20% to 25% range and to prevent hydrops.

38
Q

If possible, transfusions are given up to _____ weeks with delivery at ____ weeks’ gestation

A

34 weeks

36 weeks

39
Q

Other treatments to desensitize the mother (maternal immunomodulation)

A
  • Intravenous immunoglobulin with or without plasmapheresis
  • Glucocorticoids
  • Administration of recombinant D-specific antibodies that do not destroy RhD-positive red cells
40
Q

Indications for immediate exchange transfusion in neonates:

A
  • The cord blood hemoglobin level is significantly less than normal (perhaps a threshold of ≤110 g/L).
  • The bilirubin level is greater than 4.5 mg/dL.
  • Cord blood bilirubin is rising rapidly (>0.5 mg/dL per hour)

The aim of treatment is to prevent bilirubin neurotoxicity.

Blood component: ABO and Rh compatible, negative for offending antibody(ies), crossmatch compatible with maternal serum

41
Q

Indications for “late” exchange transfusions

A

Serum bilirubin levels threatening to exceed ~20–22 mg/dL in term infants, lower levels in preterm or sick infants

42
Q

Double-blood-volume exchange volume

  • Term infants:
  • Preterm infants:
A
  • Term infants: 170 mL/kg
  • Preterm infants: 200 mL/kg
43
Q

Used to enhance recovery of the hemoglobin concentration and decrease the need for postnatal exchange transfusions.

It is also useful in Kell antigen–mediated alloimmune disease because, in that case, erythroid hypoplasia is an important factor.

A

Recombinant human erythropoietin, 200 U/kg, subcutaneously, three times per week for 6 weeks

44
Q

Used prophylactically in any patient with moderate or severe hemolysis or in infants with bilirubin levels rising at more than 0.5 mg/dL per hour

Mainstay of treatment for unconjugated hyperbilirubinemia.

The object is to prevent bilirubin neurotoxicity

A

Phototherapy

Intensive phototherapy (≥30 μW/cm2) in the 430–490 nm band is delivered to as much of the infant’s surface area as possible.

45
Q

Indications for initiating intensive phototherapy in full-term infants with HDFN

A

TSB levels
* ≥5 mg/dL at birth
* ≥10 mg/dL at 24 hours
* ~13–15 mg/dL at 48–72 hours

The effectiveness is influenced by the wavelength and irradiance of light, the surface area of exposed skin, and the duration of exposure

In preterm or sick infants, phototherapy is recommended at lower levels to avoid potentially risky exchange transfusions

46
Q

TRUE OR FALSE

RhIg prophylaxis

Very effective when administered to women exposed to RhD-positive RBCs either from pregnancy or from transfusion, but not effective for preventing or reducing the severity of HDFN after alloimmunization has occurred

A

TRUE

Very effective when administered to women exposed to RhD-positive RBCs either from pregnancy or from transfusion, but not effective for preventing or reducing the severity of HDFN after alloimmunization has occurred

47
Q

Intramuscular doses of ___________ of RhIg to nonsensitized RhD-negative mothers within ______of delivery have decreased Rh immunization by greater than 90%.

A

100 to 300 μg of RhIg

72 hours

In the absence of Rho(D) immunoglobulin (RhIg) prophylaxis, sensitization occurs in 7% to 16% of women at risk, within 6 months after delivery of the first RhD-positive ABO-compatible fetus

48
Q

If the mother is RhD negative with an RhD-positive newborn, administration of antepartum RhIg at _________ weeks has decreased immunization to about 0.1%.

A

28 weeks

Rarely, sensitization may occur before the 28th week.

49
Q

The standard dose of 300 μg of RhIg (1500 IU) affords protection for a fetomaternal transfusion of _______ mL of RhD-positive red cells or ______ mL or RhD-positive whole blood.

A

15 mL of RhD-positive red cells

30 mL or RhD-positive whole blood.

50
Q

An important complication of elevated serum levels of indirect bilirubin, caused by bilirubin pigment deposition in the basal ganglia and brainstem nuclei, leading to neuronal necrosis

A

Kernicterus


51
Q

Advocated by some for premenopausal women to prevent primary RBC alloimmunization

A

Transfusion of blood phenotypically matched for D and for the Kell (K1) antigen

WILLIAM'S HEMATOLOGY (109 decks)

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