indirect antiglobulin testing Flashcards
immediate spin test
- IgM antibodies
- direct test
37C incubation
- detects complement
- IgG antibody
coombs test
- IgG lattice with IgM addition
- removal of unbound material in plasma
- enhancements
LISS
reduce zeta potential
PEG
remove water volume
albumin
increase collisions
bromelin
reduces steric hinderence
polybrene
polymer non specific binding
purpose for monoclonal reagents
binding site specificity for what we want only - reduce false pos
purpose for cell washer
wash step for vol and number of washes standardized - reduce false neg
solid phase
splits open red cells to better adhere and read
when are enhancements used
before incubation period to reduce time
indirect testing
- what has attached to cell in vitro
- is there antibody present
- what we run in lab with 37 incubation
- in vitro
direct testing
- hase Ab found Ag within the body
- in vivo
antibody screen
presence of clinically significant immune stimulated (IgG) antibodies in patient plasma
IAT
indirect antibody test -> coombs
which of the following reagents is used to facilitate hemafflutination following the sensitization of red cells with IgG antibody
- anti human globulin
- low ionic strength saline
- polyethylene glycol
22% bovine albumine
anti human globulin
- coombs reagent to help IgG cells to agglutinate
after the addition of IgG coated RBCs (check cells) to a negative AHG reaction during Ab screen, a negative reaction is observed. Which of the following is the correct interpretation?
- Ab screen is neg
- Ab screen needs to be repeated
- saline wash was adequate
- Ab screen is pos
Ab screen needs to be repeated
- check cells should not be negative reactions, anti Ab added preferentially bound circulating Ab not red cell bound Ab
coombs test reagent
anti-human antiglobulin
- IgM anti - IgG
what is the purpose for anti-antibody addition in coombs test
- grabs red cell bound IgG (multiple) to form agglutination lattices
describe check cells
IgG coated cells
- determine adequate washing of coombs phase
if a check cell reaction is negative what does that indicate
inadequate washing, AHG bound circulating Ab not red cell IgG, repeat teting
which is more likely in coombs phase: false neg or false pos
false neg
list possible false negatives in coombs testing AHG step
- incorrect ratio of plasma to red cells
- aged/hemolyzed cells
- excessive washing
- bad centrifuge calibration
- leftover wash dilution
list possible false negatives in check cell step of coombs testing
- leftover Ab bound check cells
- insufficient washing
- insufficient incubation
lab controlled antigen-antibody binding
- time
- temp
- centrifugation
antibody- antigen controlled factors
- affinity
- avidity
- zeta potential
- steric hinderance
- hydrophobic` bond
describer gel reactions
precipitation
describe solid phase reaction
adherence
