HDFN & Hemolytic Anemias Flashcards
What is the definition of hemolytic disease of the fetus and newborn (HDFN)?
Results from immune destruction of RBCs of fetus or newborn due to sensitization by the mother’s IgG antibody
Maternal antibody crosses the placenta and reacts with an RBC antigen inherited from the father.
What are the criteria necessary for HDFN to develop?
Mother must be sensitized to fetal RBC antigens, typically through previous pregnancy or transfusion.
What are the three classifications of HDFN?
- Rh
- ABO
- Other/non-Rh antibodies
How does bilirubin metabolism differ in the fetus versus the newborn?
In the fetus, bilirubin is conjugated in the maternal liver; in the newborn, the liver is unable to conjugate large amounts of bilirubin.
What are the intervention procedures used in the diagnosis and management of HDFN?
Includes laboratory testing, monitoring bilirubin levels, and possible transfusions.
What treatments are available for HDFN?
Includes phototherapy, exchange transfusion, and administration of Rh immune globulin.
What blood components are preferred for intrauterine or exchange transfusions?
Red blood cells, preferably less than 7 days old.
What is Rh Immune Globulin (RhIG)?
A medication used to prevent Rh sensitization in Rh-negative mothers.
What are the key aspects of administering RhIG?
- Dosage
- Eligibility criteria
- Timing intervals
What does a positive rosette test indicate?
Suggests fetomaternal hemorrhage.
What is the significance of the Kleihauer-Betke test?
Used to quantify fetal-maternal hemorrhage.
What is an autoantibody?
An antibody produced by the immune system that targets the body’s own cells.
What are the types of immune hemolytic anemias?
- Warm autoimmune hemolytic anemia (WAIHA)
- Cold agglutinin disease
- Drug-induced hemolytic anemia
What are pathologic cold autoagglutinins?
Antibodies that cause agglutination at lower temperatures, leading to hemolysis.
What complications can arise from HDFN during pregnancy?
- Mild anemia
- Hyperbilirubinemia
- Jaundice
- Severe enlargement of the liver and spleen
- Hydrops fetalis
What is kernicterus?
A severe condition resulting from high levels of unconjugated bilirubin affecting the brain.
What occurs when fetal RBCs are destroyed?
Anemia limits oxygen carrying ability, leading to compensatory erythropoiesis in the liver and spleen.
What is hydrops fetalis?
A condition where the fetus accumulates fluid due to severe anemia.
What is the role of glucuronyl transferase in bilirubin metabolism?
Converts indirect bilirubin to a conjugated form in the liver.
What laboratory findings indicate severe HDFN?
Elevated indirect bilirubin levels and positive direct antiglobulin test (DAT).
What is the primary characteristic of moderately affected D-positive infants?
Jaundice develops within the first few days of life.
What is the treatment required in cases of Rh HDFN?
Exchange transfusion to prevent kernicterus.
What is the most common form of HDFN?
ABO HDFN.
Is ABO HDFN preventable?
No, it can affect the first pregnancy.
What treatment is effective for mild cases of jaundice in ABO HDFN?
Phototherapy.
What is a common blood type of mothers who have ABO HDFN?
Group O.
What antibodies do group O mothers typically have in higher titres?
IgG anti-A and anti-B.
When does jaundice typically develop in infants with ABO HDFN?
Within 12 to 48 hours after birth.
What is the most significant laboratory finding for diagnosing ABO HDFN?
Positive direct antiglobulin test (DAT) on cord blood.
What is required for any IgG antibody to cause HDFN?
Fetal RBCs must possess the antigen, and it must be well developed at birth.
What is the second most common antibody causing HDFN?
Anti-c.
What is the bilirubin level indicating severe HDFN?
Cord bilirubin > 68 umol/L.
What is kernicterus associated with?
Bilirubin levels > 300 umol/L.
What prenatal assessment is done early in pregnancy to identify Rh negative candidates?
Group and antibody screen.
What is a significant titre change indicating further monitoring?
Increase of 2 dilutions or more.
What test is performed on the baby’s sample immediately after delivery if an IgG antibody is discovered?
Cord blood testing.
What does the Liley graph estimate?
Severity of hemolytic disease based on bilirubin levels in amniotic fluid.
What does a zone III result on the Liley graph indicate?
Severe potentially life-threatening hemolysis.
What does an amniocentesis assess in relation to HDFN?
The status of the fetus using amniotic fluid.
What is the purpose of elution testing in HDFN?
To identify antibodies from RBCs when DAT is positive.
What is hydrops fetalis?
A condition where the baby has severe edema of the entire body and difficulty breathing
Hydrops fetalis can indicate serious underlying issues, including heart failure or severe anemia.
What is the role of Rh immune globulin (Rhogam)?
To prevent immunization to D in Rh-negative mothers who may be exposed to Rh-positive fetal cells
Rhogam is derived from human plasma and is crucial in preventing Rh HDN.
What are the indications for administering Rhogam?
- Spontaneous or therapeutic abortion
- Amniocentesis
- Chorionic villus sampling
- Antepartum hemorrhage
- Ectopic pregnancy
- Blunt abdominal trauma
- Fetal death
Rhogam is given to prevent sensitization in various scenarios involving Rh incompatibility.
How does Rhogam work?
It contains antibodies to the Rh factor that attach to fetal RBCs in maternal circulation, preventing alloimmunization
This mechanism helps protect future pregnancies from Rh incompatibility.
What is the success rate of Rh immune globulin when given correctly?
Greater than 99% when given at 28 weeks and within 72 hours of delivery of an Rh-positive child
Rhogam is highly effective in preventing sensitization during current pregnancies.
What is the purpose of an exchange transfusion?
- Increase hemoglobin
- Decrease bilirubin
- Remove maternal antibodies
- Replace sensitized cells
It is performed to treat anemia and hyperbilirubinemia in newborns.
What type of blood is used for exchange transfusions?
- O Rh negative packed cells
- AB FFP for hematocrit of about 50%
- Fresh blood less than 7 days old
Exchange transfusions must be compatible with the mother’s blood to avoid complications.
What are the risks associated with intrauterine transfusion?
1-2% risk of fetal loss
Intrauterine transfusions are performed to manage anemia before delivery.
What is the significance of the weak-D test?
If Rh negative, a weak D positive result is treated as Rh positive
This test is important for determining the appropriate administration of Rhogam.
Fill in the blank: Rh immune globulin is given to prevent the mother’s immune system from producing its own _______.
Rh antibodies
True or False: Rh immune globulin is effective once anti-D antibodies have formed.
False
What is the recommended duration for allowing smears to dry?
The longer they air dry, the better they fix and stain.
What is the fixation solution used for fetal cell identification slides?
80% ethyl alcohol for 5 minutes.
How frequently should new fixation solutions be made?
Every two weeks.
What is the first step after placing slides in the citrate phosphate buffer solution for fetal cell identification?
Wash under running water and let air dry.
What color should fetal cells stain in the procedure?
Red or dark pink.
What is the formula to calculate FMH volume?
Fetal cells/100 x 5000.
What is Wharton’s jelly?
A gelatinous intercellular substance which is the primitive mucoid connective tissue of the umbilical cord.
What is a key characteristic of immune hemolytic anemia?
RBCs are destroyed prematurely due to an immune-mediated process.
What are the two types of hemolysis in immune hemolytic anemia?
Intravascular hemolysis and extravascular hemolysis.
What laboratory finding indicates intravascular hemolysis?
Hemoglobinemia and hemoglobinuria.
What is a common laboratory finding in extravascular hemolysis?
Spherocytosis.
What are the two main types of AIHA?
- Warm autoimmune hemolytic anemia
- Cold autoimmune hemolytic anemia
What is a common characteristic of warm AIHA?
Positive DAT when tested with polyspecific reagent.
What is a common treatment for persistent hemolysis post-splenectomy?
Immunosuppressive drugs
What are pathological cold autoantibodies classified into?
- Primary Cold Agglutinin Disease (CAD)
- Cold Agglutinin Syndrome
- Paroxysmal Cold Hemoglobinuria (PCH)
What is a common symptom of cold autoimmune hemolytic anemia?
Acrocyanosis of hands, feet, ears, and nose.
What is the recommended method for performing a cold agglutinin screen?
Collect and leave specimen at 37ºC to clot or warm EDTA sample for > 15 min at 37ºC before separating.
What is the common antibody involved in infectious mononucleosis?
IgM anti-i.
True or False: Cold autoantibodies are present in all normal human sera.
True.
What is the common autoantibody associated with cold agglutinin disease?
IgM anti-I
Seen in at least half of the cases of pneumonia due to mycoplasma pneumonia
What infections are associated with paroxysmal cold hemoglobinuria?
Viral infections such as mumps, measles, chickenpox, and flu
What characterizes paroxysmal cold hemoglobinuria?
Passage of urine containing hemoglobin and/or methemoglobin
What type of hemolysis occurs in paroxysmal cold hemoglobinuria?
Intravascular hemolysis due to exposure to cold
What is the specific autoantibody in paroxysmal cold hemoglobinuria?
IgG = detectable biphasic autohemolysin
What triggers hemolysis in paroxysmal cold hemoglobinuria?
Antibody binds to red cells at low temperatures and causes intravascular hemolysis via complement activation
What does a positive Landsteiner test indicate?
Autoantibody has anti-P specificity
What is the primary symptom of paroxysmal nocturnal hemoglobinuria?
Passage of dark urine in the morning
What is the most important drug known to cause a positive DAT?
Aldomet (alpha-methyldopa)
What happens when a drug adsorbs onto the RBC membrane?
The drug-antibody combination becomes adsorbed onto the red cells, causing membrane modification
What is the most common drug-induced hemolytic anemia mechanism?
Drug absorption (hapten) mechanism
What is required for the drug absorption mechanism to occur?
Drug must be absorbed nonspecifically to red cells and elicit an immune response
What is the common drug associated with the immune complex mechanism?
Quinidine
What should be done if transfusion is essential for AIHA patients?
Transfuse the least incompatible blood
