Flashcards in Transfusion Medicine II Deck (26)
Hemolytic Disease of the Newborn
A hemolytic process in the perinatal period, resulting in abnormal RBC destruction with multiple causes:
- Alloimmunization to RBC antigens
- Congenital RBC defects (membranes, enzymes, etc.)
- Acquired RBC defects usually secondary to infection
How does alloimmunization of an Rh- woman in pregnancy occur?
1. Mother is exposed to the Rh+ Ag on the fetus
2. Mother is sensitized and will make IgG VS the fetus
When is the greatest risk for D-alloimmunization occur?
What can be seen in the smear of an infant with HDN?
Erythroblastosis fetalis - RBC precursors are seen in the blood which is an abnormal sign
What is the DAT test on a newborn with HDN?
It will be positive
Why is there hepatosplenomegaly in HDN?
Most fetal hematopoiesis occurs in liver and spleen
so it causes hepatosplenomegaly
What are some other signs of HDN?
Jaundice - hyperbilirubinemia due to lysis of RBCs
￼Kernicterus is the staining of the basal ganglia due to severe hyperbilirubinemia which results in neural damage
What is ABO HDN?
Almost exclusive to Group O mothers as they make anti-A, anti-B and anti-A,B that could be IgG in nature which can cross the placenta and sensitize the RBCs.
What is the DAT result for ABO HDN?
The DAT will be positive due to IgG attached to RBCs in vivo
How is HDN prevented?
Protein concentrate of “Anti-D”, prepared from pools of serum from previously-sensitized females is injected IV or IM.
How are SENSITIZED pregnancies to Rh managed - that is, alloantibodies already have been formed?
- Early delivery
- Noninvasive fetal blood flow monitoring - MCA flow velocity
- Exchange transfusion - remove sensitized RBCs
What are unexpected autoantibodies and what are they detected by?
Directed against generic RBC membrane antigens and they are detected by the IAT.
What is the action of most unexpected autoantibodies?
Most are clinically silent. Only some cause hemolysis.
What are warm auto-Ab?
The “Warm” ones are usually IgG in nature, can coat the patient’s RBSs and / or be in the patient’s plasma
• Can cause a positive DAT and / or IAT
• They function at 37 ˚C
What are cold auto-Ab?
The “Cold” ones are often IgM in nature and can activate
• They function at less than 25 ˚C
What is the result of Warm auto-Ab on the crossmatch test?
Warm autoantibodies in plasma cause XM-incompatibility against ALL RBC units!!!
What are some of the major causes of autoantibodies?
- Systemic lupus erythematosis
- Chronic lymphocytic leukemia
What are some lab markers of autoimmune hemolysis?
• Falling hemoglobin (Hgb) and hematocrit (Hct)
• Elevated total LDH
Warm Autoimmune Hemolytic Anemias
- Pathogenic IgG autoantibody coats RBCs (positive DAT) - Extravascular clearance of RBCs - splenic
What is the main treatment of Warm Autoimmune Hemolytic Anemias?
Cold Agglutinin Disease
- Moderately severe anemia, symptoms related to degree
- Acrocyanosis, precipitated by exposure to cold
What is the main population of cold agglutinin disease?
What are the lab findings of cold agglutinin disease?
- Cold refers to Ag-Ab reactions taking place at 25˚C or colder temperatures
- Positive DAT due to anti-complement only
- Cold agglutinin detectable in plasma and on RBCs
What are the main treatments of cold agglutinin disease?
Keep the patient warm