Midterms: AHG & Pretransfusion Flashcards
ANTI-HUMAN GLOBULIN (AHG) REAGENT
• Other name:
Coombs Reagent
Reagent that has been prepared by injecting animals (rabbits) with
human antibody molecules and complement proteins. The sensitized
animal which produced antibodies against IgG and complement
proteins
AHG REAGENT
This reagent contains a blend of antibodies for IgG (Anti-IgG)
and complement proteins (Anti-C3b, Anti-C3d)
Polyspecific Anti Human Globulin Reagent
This reagent contains antibody of only one specificity
MONOSPECIFIC ANTI HUMAN GLOBULIN (COOMBS’) REAGENT
Describe AHG Reagent
• AHG antibodies act as bridges that induce agglutination to RBCs coated with human IgG or complement.
Anti human globulin reagent is used to detect
IgG or complement
sensitized on red blood cells.
Explain neutralization
Any unbound antibody or complement present in serum can
potentially bind to the AHG reagent and inhibits its reaction with
antibody or complement molecules attached to the RBC
Any unbound antibody or complement present in serum can
potentially bind to the AHG reagent and inhibits its reaction with
antibody or complement molecules attached to the RBC
Neutralization
Used to detect in vivo-sensitized red blood cells withimmunoglobulin, or complement or both.
DAT
Applications for DAT
Alloimmune Hemolysis
Rh HDN
HDFN
Autoimmune Hemolysis
Drug induce-immune mediated hemolysis
Drug induced-immune mediated hemolysis consist of:
Methyldopa
Penicillin (High dose)
Cephalosporin
Procainamide
Can you name examples of blood group autoantibodies?
Autoanti I : Infectious mononucleosis
Autoanti P: PCH, Donath Landsteiner, Cold Autoantibody
Autoanti Kidd: Proteus Mirabilis
Applications of IAT
Crossmatching
-Detection of antibodies in pregnant women
-Screening and identification of antibody specificity using a panel of
red blood cells with known antigenic profile
-Determination of red blood cell phenotype using known antisera
(e.g. Du testing)
• Titration of incomplete antibodies
Factors Affecting AHG TEST
Ratio of serum to cells
Reaciton Medium
Temperature
Incubation Time
Washing of cells
Saline for Washing
Addition of AHG
Centrifugation
SALINE FOR WASHING
• Ideally, it should be fresh or alternately buffered to a _______
ph 7.2-7.4
ERRORS IN AHG TESTING FALSE -
Failure to wash cells
Interruption in testing
Improper procedure
Improper reagent storage
Neutralization
Saline Soluotion is Old
aHG is aged
Errors in AHG False +
Particles or contaminants
Improper procedure
Cells with positive DAT results
Complement coated RBCS
The cells are used as a quality control measure for negative indirect direct anti globulin test performed in test tubes,
Coombs control red cells
Define pretransfusion compatibility testing
series of testing procedure and processes with the objective of ensuring
the best possible results of a blood transfusion
series of testing procedure and processes with the objective of ensuring
the best possible results of a blood transfusion
Pre-transfusion compatibility testing
Enumerate the components included in compatibility testing.
ABO GROUPING
RH TYPING
CROSSMATCHING
HISTORICAL RECORD CHECK
Screening unexpected antibodies
Alloantibody identification
State the fundamental rule in the selection of donor blood in crossmatch
ABO and Rh- group specific blood between donor and recipient
• Donor unit- should be the same as the Pt’s ABO and Rh group.
most important consideration in pretransfusion compatiblity testing
Positive patient identificaition
