AHG Flashcards
AHG is also known as?
Coomb’s test
AHG
this test is used to?
principle
detect the presence of human globulin molecules either bound to the red cells or free in serum
Coomb’s test make use of reagents produced by?
rabbits
which will react to human antibodies
used to detect antibody binding to antigen on the surface of RBCs that happens in vivo
Direct Antihuman Globulin Test
IAT is used to detect for the?
in vitro sensitization of red blood cells with blood group antibodies
reagent that contains anti-IgG and C3D
polyspecific AHG
reagent that contains only anti-IgG
Monospecific AHG
DAT
in vivo or vitro?
in vivo
IAT
in vivo or in vitro?
in vitro
storage req for reagent
stored at 2-8 centrigrade and must be at room temperature prior to use
make sure it is beyond its expiry date before using
steps of DAT
add — of the AHG reagent to the cell button and resuspend the cells?
what step number?
2 drops of AHG reagent
step 3
DAT
after preparing 3-5% rbc suspension, what’s the next step?
place 1-2 drops of cell suspension and wash it with saline 3-4 times
steps of DAT
after AHG reagent, what’s the next step?
centrifuge at 3200 rpm for 15 seconds and read and grade the reaction
steps of DAT
what will you do if it is negative?
add 1 drop of check cells to the negative test tube.
this should give a positive result
steps of IAT
after placing 2 drops of prepared rbc suspension, what’s the next step?
add patient’s serum into the same test tube
steps of IAT
incubate the tube at — in a water bath for —
step 4
incubate 37C for 15 minutes
steps of IAT
after incubation, what’s the next step?
centrifuge and resuspend then observe for agglutination or hemolysis
steps of IAT
if no agglutination, what will u do?
wash the serum-cell mixture 3 times by NSS
after 3rd washing, centrifuge @ 3200 rpm for 15 secs
indicates a positive result of DAT
agglutination
agglutination in DAT is due to?
in vivo sensitization of antibodies coating to the patient’s RBCs
positive result of IAT
agglutination
Coomb’s test (AHG) was named after who?
Coombs, Mourant, and Race (1945)
they described a test for detecting nonagglutinating Rh antibodies
DAT is used to diagnose —
- HDFN
- HTR
- autoimmune hemolytic anemia
IAT is used to demonstrate in vitro reactions between red cells and coating antibodies, as in —
- antibody detection
- antibody identification
- blood goruping
- compatibility testing
false + results is caused by — (10)
enumerate
- improper specimen (refrigerated or clotted)
- autoagglutinable cells
- bacterial ocntamination of cells or saline used in washing
- cells with positive DAT for the IAT
- saline contaminated with heavy metals or colloidal silica
- dirty glassware
- overcentrifugation and overreading
- polyagglutinable cells
- preservative-dependent antibody LISS reagents
- contamianting antibodies in the antihuman globulin reagent.
may cause in vitro complememt
false negative may be due to —
enumerate the 7
- inadequate or improper washing of RBCs
- deterioration of reagent or neutralization
- AHG reagent not added
- serum not added in IAT
- serum not reactive because of complement inactivation
- inadequate incubation condition of IAT
- cell suspension either too heavy or too weak
- undercentrifugation
- poor reading technique
enumerate the factors affecting the sensitibity of IAT
- temperature
- ionic strength
- ratio of serum to cells
- pH of the reaction mixture
- incubation time
