Ch. 12 - Sources of error Flashcards
What are some important sources of preanalytic error in pretransfusion testing?
Those related to specimen collection, handling, and processing. Specifically, consider tourniquet application, AC:blood ratio, proper inversion and storage.
What are four types of ABO discrepancies?
- Weak or loss of expected RBC antigen
- Presence of unexpected antigen-like reactivity
- Weak or loss of expected antibody
- Presence of unexpected antibody reactivity
How may ABO discrepancies manifest in pretransfusion testing?
- Disagreement between current and historical type
- Discrepancy between forward + reverse rxn
- Weaker reactivity than expected
- Mixed field reactivity
What are some causes of weak or absent antigen?
A/B blood subgroups
Hematologic malignancies (fewer antigens formed).
Extremes of age
Solid organ cancers (increased secreted substance).
Chimerism
What are some causes of unexpected antigen-like reactivity?
Polyagglutination (Rouleaux, Wharton’s jelly, Cold autoantibodies, Microbial cryptantigens)
Stem cell transplantation
B(A) phenomenon
Fetomaternal hemorrhage, chimerism
What are some causes of weak or absent antibody?
Extremes of age
Immunosuppression/immunodeficiency
What are some causes of unexpected antibody activity?
IVIG, RhIG, transfusion
ABO subgroups
Cold agglutinins and true alloantibodies
What are the three mechanisms for drug-related RBC agglutination?
Antigen-antibody complexes
Antibody adsorption onto RBCs (haptens)
Non-direct induction antibodies (eg alphamethyldopa, penicillamine)
What are some causes of pseudoagglutination (non-immune)
Rouleaux, fibrin clots, agglutination due to albumin and plasma expanders.
What are some substances that can cause antibody-mediated RBC agglutination without being specific to RBC antigens?
LISS, antibiotics (penicillin, chlormaphenicol), lactoase/lactate, thimerosal, sugars, EDTA. Weird stuff.
