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40 Cards in this Set
- Front
- Back
What is an ABO discrepancy?
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-ABO forward/ front type does not match ABO reverse/ back type
-Mixed-field agglutination |
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Causes of ABO Discrepancies
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-Forward: Extra antigens, missing antigens and Mixed field agglutination
-Reverse: Extra antibodies, missing antibodies |
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Missing Antigens (forward)
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ns
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Extra antigens (forward)
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ns
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Mixed-Field agglutination (forward)
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ns
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Extra Antibodies (reverse)
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ns
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Missing Antibodies (reverse)
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ns
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Why do we observe discrepancies in ABO Forward/ Front type?
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-Mixed Field agglutination
-Extra Antigens: B(A), Acquired B, Antibody Coated RBCs |
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Why do we observe mixed-field agglutination?
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"Artificial" causes
-blood transfusion -fetal/ maternal bleed -hematopoietic progenitor cell transplant (HPC) |
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A3 subgroup
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inherited mutation in A gene
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A3 subgroup
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-weaker than A2 with anti-A
-Characterized by mixed-field agglutination with Anti-A and Anti-A,B -Serum occasionally contains anti-A1 (will make sometimes) |
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Chimerism
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Fraternal twins
mosaicism from despermy |
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How is mixed field agglutination characterized
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by small tightly agglutinated clumps of cells which chip off the buttom first followed by a stream of free cells giving a smoky looking background or vice versa
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Why is it important to recognize mixed field?
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-May provide unrecognized clinical information about patient
-May identify mistransfusion |
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Why do we observe extra antigen?
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B(A)
Acquired B Antibody coated RBCs |
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Acquired B
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ns
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Acquired B
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-Found in A1 individuals
-Monoclonal anti-A most sensitive -found in bacterial infection (deacetylase enzyme) |
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Acquired B Antigen
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ns
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Antibody coated RBCs
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DAT positive RBCs may cause spontaneous agglutination
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Why do we observe missing antigen?
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-Subgroups of A/B
-mutations in A or B gene resulting in altered transferase which weakly puts stuff on. |
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A2 phenotype
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Qualitative difference
A2 can make anti A1 why? transferase activity differs, A1 transferase adds GalNAc to repetitive Type 3H and Type 4H |
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Cold Autoantibody
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ns
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Cold-reactive Alloantibodies
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ns
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Rouleaux
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ns
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Missing Antibodies
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ns
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Missing Antibodies
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ns
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Resolving ABO Discrepancies
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1.Assume either forward or reverse type is correct
2.Assess if discrepancy in opposite typing is due to extra or missing antigens/antibodies 3.review patient history for clues to determining cause of discrepancy 4.perform testing to verify cause of discrepancy and interpret ABO |
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Repeat ABO type-Why?
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many labs routinely repeat ABO (compare results)
mistakes happen |
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patient transfused
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mixed field
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infused with ABO compatible plasma products
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extra antibody
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Received IVIG
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extra antibody
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6 months or younger
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missing antibody
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testing RBCs to resolve ABO discrepancies
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type with: Anti-A,B, Anti-A1 lectin, different manufacturer of Anti-A, -B, -AB, Acidified Anti-B, lectin Kit
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Testing RBCs to resolve ABO Discrepancies
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-incubate -A,-B,-A,B at Room temp
-treat to remove antibody -look at RBCs in plasma to assess for rouleaux -phenotype patient if alloantibody is identified |
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Anti-A,B reagent
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polyclonal or monoclonal
FDA requirement-reacts with Ax RBCs |
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