Quiz 10 Flashcards
What is Autoimmune Hemolytic Anemia(AIHA)?
Destruction of RBCs as a result of antibody production
What are the two types of Autoimmune Hemolytic Anemia (AIHA)?
- cold and warm AIHA
- drug-induced AIHA
What do suppressor T cell do?
induce tolerance to self-antigens by inhibiting activity of B cells
What are autoantibodies?
Antibodies directed against an individual’s own RBCs
What results in autoantibody production?
loss of suppressor T cells function
What do autoantibodies react with the most?
high prevalence antigens
T or F, all autoantibodies cause RBC destruction.
False, Some individuals produce an autoantibody that attaches to their RBCs, but does not cause RBC destruction
What is a positive DAT or positive autocontrol indicative of (if the patient has not been transfused in the last 3 months)?
the presence of a WARM autoantibody coating the RBC in vivo
What is a positive DAT or positive autocontrol indicative of, if the patient HAS BEEN transfused in the last 3 months?
alloantibody coating the transfused cells; high prevalence antigen (not their own cells)
What do the column agglutination (Gel) and solid phase methodologies enhance?
the sensitivity in detection of autoantibody coated RBCs, especially with IgG
(easier to detect RBC w/ Autoantibodies)
What type(s) of testing do autoantibodies complicate?
- ABO/Rh
- antibody screen
- crossmatches
(routine blood testing)
What is Compensated anemia?
rate of RBC production nearly equals rate of RBC destruction
What lab results may indicate Compensated anemia?
- reticulocyte count is elevated
- Mild decrease in hemoglobin/hematocrit
What is uncompensated anemia?
RBC destruction rate exceeds RBC production rate
What can appear microscopically, on a peripheral smear, with a uncompensated anemia patient?
polychromasia (reticulocytes) or spherocytes
What lab results may indicate uncompensated anemia?
- Increased MCV (Macrocytosis (reticulocytes))
- Unconjugated bilirubin
- LDH increased
- Haptoglobin markedly decreased
What is the percentage of AIHA cases are…:
1. Warm AIHA
2. Cold AIHA
3. Drug Induced AIHA
- 70%
- 18%
- 12%
At what temperature are BENIGN cold autoantibodies detected?
4C
How do you resolve false positive results due to cold agglutinins?
wash patient RBCs with normal saline at 37°C (pre-warm technique)
What can be used instead of the prewarm technique for resolving cold agglutinins?
Dithiothreitol (DTT)
[breaks down the disulfide bonds]
What will indicate cold agglutinins during blood testing?
extra back type reactions
What is cold agglutinin disease?
The cold autoantibody reacts optimally at 4°C but also reacts above 30°C
Who would most likely have cold agglutinin disease?
patients older than 50 years old
What is the cause of cold agglutinin disease?
idiopathic
What antibody is associated with cold agglutinin disease?
anti-I
What symptoms are associated with cold agglutinin disease?
- acrocyanosis
- weakness
- pallor (pale af)
- weight loss
What is Acrocyanosis?
numbness in the extremities due to external temperature dropping (winter)
cold agglutinins are activated causing RBC agglutination and complement fixing
What lab results are associated with cold agglutinin disease?
- DAT positive for complement
- cold autoantibodies in the plasma with a titer >1000 at 4°C
What would be seen in the peripheral smear of a patient with cold agglutinin disease?
- agglutinated RBC
- polychromasia
- Reticulocytosis
What other disease/infections can have anti-I antibody or Secondary AIHA?
- Mycoplasma pneumoniae
- Infectious mononucleosis
Who is most likely to have Paroxysmal Cold Hemoglobinuria?
Children who have had viral illness such as measles, mumps, chicken pox, infectious mono, flu
What type of antibody is associated with Paroxysmal Cold Hemoglobinuria?
a biphasic hemolysin IgG antibody against P antigen
What is a biphasic hemolysin?
an antibody that binds to RBCs at lower temperatures and fixes complement; hemolysis occurs when sensitized RBCs circulate and are exposed to 37°C
(binds to RBC + fixes complement in cold temp, activates and sensitizes in warm temperatures)
What is Paroxysmal Cold Hemoglobinuria?
- Patients have intermittent episodes of hemoglobinuria upon exposure to the cold
- can result in severe anemia with hemoglobin as low as 4-5 g/dL
What symptoms are associated with Paroxysmal Cold Hemoglobinuria?
- sudden onset of fever
- shaking chills
- malaise
- abdominal cramps
- and back pain
What is the laboratory test for PCH?
Doneth-Landsteiner test
What can appear microscopically, on a peripheral smear, with a WARM AIHA patient?
- polychromasia
- macrocytosis (reticulocytes)
- nucleated RBCs
- spherocytes (extravascular hemolysis)
How do spherocytes form due to warm AIHA?
- RBC sensitized with IgG and/or complement
- Sensitized RBC bind to the Fc portion of IgG and for C3b of the splenic macrophages
3a. completely phagocytized
3b. just a portion of the membrane is bitten off and the RBCs reseal their membrane and form spherocytes
What diseases/infections are a result of severe warm AIHA?
- an intravascular hemolysis
- hemoglobinemia
- hemoglobinuria
- increased LDH
- DIC may ensue
What percentage of Warm AIHA cases have both IgG and complement on the RBCs?
67%
What percentage of Warm AIHA cases have only IgG?
20%
What percentage of Warm AIHA cases have only complement? (undetectable IgG)
13%
What does NOT react with warm autoantibodies?
Rh null cells
Why would alloantibodies be “masked” in IAT testing?
both warm autoantibodies and alloantibodies react at IAT, so only the warm autoantibodies would be detectable and the alloantibodies would be “masked”
Why are warm autoantibodies considered a “panagglutinin”?
It STRONGLY reacts to Rh blood groups, Rh+ AND Rh-
Why is ABO typing NOT affected by Warm AIHA?
ABO testing involves DAT; Warm AIHA involves IAT
What can NOT be performed if the DAT is positive for warm autoantibodies?
- weak D testing
- any IAT phenotyping in general (due to false positives)
If there is a small amount of (warm) autoantibodies, what would be positive?
DAT
If there is a LARGE amount of (warm) autoantibodies and saturated RBC, what would be positive?
- DAT
- IAT (antibodies in the plasma)
How do you determine specificity of warm autoantibody?
eluate
T or F, Does positive DAT ALWAYS indicate autoantibodies?
No, if patient recently transfused, the alloantibodies are sensitizing the transfused RBC
What would show mixed field agglutination, high prevalence antigen or autoantibody?
high prevalence antigen (alloantibody reaction/ due to transfusion)
What is ALSO a panagglutinin, other than warm autoantibodies?
high prevalence antigen
What would indicate that the panagglutinin is a high prevalence antigen, rather than warm autoantibodies?
- Negative autocontrol
- transfused within the last 3 months
- mixed field
What type of test would “unmask” alloantibodies, when both autoantibodies and alloantibodies are present?
- Lo-ion
- 1:5 dilution (plasma:saline), may dilute out alloantibody
- Warm autoadsorption (can’t do on preggo/transfused w/in 3 months)
- Warm Alloadsorption (ok for preggo/transfused recently)
What is Warm autoadsorption?
removing the attached antibody off of the patient RBCs and then adsorbing antibody from the patient plasma sample onto the patient’s RBCs
The presense of _______ makes all RBC units incompatible
warm autoantibodies
Why is giving “e” negative blood to patients with e specificity considered controversal?
E is homozygous, so the patient can make an anti-E alloantibody
