ahg

anti human globulin (AHG)

reagent used to induce agglutination of sensitized RBCs

IgG, complement

things that coat RBCs or are unbound in plasma that bind AHG

direct antiglobulin test (DAT)

detects Ab that bound to RBCs in vivo

-”one step”

indirect antiglobulin test (IAT)

detects Ab that bound to RBCs in vitro

-”two step”

monospecific

AHG type that binds either IgG or complement (C3d/C3b)

polyspecific

AHG type that binds IgG and complement (C3d/C3b)

coombs cells (check cells)

-group O coated with human IgG or complement

-added to nonreactive cells to validate AHG presence and activity (true neg or error)

-MUST be positive

group O cells coated in human IgG or complement

what Coombs cells (check cells) are

polyspecific

type of AHG to start DAT with

AIHA, DIH, HDFN, HTR

clinical events that elicit DAT

DAT

DAT/IAT done in cases of AIHA, DI hemolysis, HDFN, HTR

pos

hemolysis may cause false pos/neg DAT

monospecific

if positive with polyspecific AHG, add … AHG

elution

step following pos with monospecific IgG AHG

-diccosiates Ab off red cells to ID Ab

C3

no further testing is needed with pos monospecific C3/IgG

allo, auto

antibodies identified with DAT 

vitro

RBCs are sensitized in vivo/vitro in IAT

vivo

RBCs are sensitized in vivo/vitro in DAT

IAT

testing done in event of:

-weak D

-antibody screen and ID

-crossmatch

-antigen typing

monospecific IgG

AHG used in IAT

37

temperature of IAT

LISS, PEG

potentiators

potentiator

-LISS or PEG in IAT

-increases sensitization

2:1

plasma:RBC ratio

30 min

incubation time for IAT with LISS and reagent to increase sensitization

6.8-7.2

optimal IAT pH

neg

false neg/pos AHG testing

-inadequate washing (AHG binds things in plasma)

-testing interrupted (bound globs dissoc)

-denatured AHG

-AHG not added

-improper centrifugation

-improper suspension

-shaking too vigorous

pos

false pos/neg AHG testing

-clotted samples, cold agglutinins

-gel separator tube

-bacterial contam saline

-dirty glassware

-overcentrifugation

eluting acid

used to remove monospecific IgG from cells in pos DAT