B3.050 Pre-transfusion Workup Flashcards
what are the 2 steps in a general RBC serological test?
sensitization: Abs binding to RBCs surface Ag
agglutination: sensitized RBCs are bridged together to form the lattice
how are serological tests read?
immediately after test is done
visual or by machine
what is the function of an antiglobulin test?
sometimes, bridging between sensitized RBCs is not strong enough to cause agglutination
anti human globulin (AHG) is then used to help enhance agglutination, usually required for clinically significant Ab detection
IgM RBC antibodies
large w 10 potential antigen binding sites
binds to Ags on adjacent RBCs forming lattice or clump
cold antibodies react best at 22 C in immediate spin phase
fixes complement and causes intravascular hemolysis
IgG RNC antibodies
smaller with only 2 antigen binding sites
binds to antigens on single RBC, so doesn’t bridge
warm antibodies react at 37 C in AHG phase
needs AHG reagent to see agglutination
what is phase 1 of the in tube test
immediate spin phase
patients serum mixed with commercial RBCs
mix, centrifuge, examine for agglutination…if positive, there is a present of cold Abs
what is phase 2 of the in tube test
37 C incubation to detect warm-reactive Abs
enhancing substances can be added
what is phase 3 of the in tube test
RBCs are washed and checked by AGT add AHG, incubation and centrifugation examine for agglutination IF NEGATIVE must re-check with a control system of IgG coated RBCs to make sure it wasn't a false negative
what are the types of antiglobulin tests?
direct antiglobulin test (DAT)
indirect antiglobulin test (IAT)
direct antiglobulin test
detects patient’s RBC that have already been sensitized with IgG or complement in vivo (Ab coated RBCs)
indirect antiglobulin test
- detects anti RBC Abs in patient’s serum
2. in-vitro coating of RBCs with antibody or complement
gel testing results
positive: agglutination at top of column
negative: unagglutinated cells pass through gel and pellet at bottom
solid phase testing results
positive: indicator RBCs diffusely adhere over the well
negative: indicator RBCs pellet to the bottom
what are the 2 primary groups of RBC Ags?
oligosaccharide (carb): ABO
amino acid sequence: Rh
what are clinically significant allo-Abs?
cause hemolytic transfusion reaction (HTR) and/or hemolytic disease of the fetus and neonate (HDFN)
mostly IgG
most important Ag group?
ABO
what Ag and Ab does type O blood have
Ag- none
Ab- anti A and anti B
what Ag and Ab does type A blood have
Ag- A
Ab- anti B
what Ag and Ab does type B blood have
Ag- B
Ab- anti A
what Ag and Ab does type AB blood have
Ag- A and B
Ab- none
most important protein based RBC Ag?
Rh
discuss the Rh genetic possibilities
2 genes on Ch1: RhCE and RhD
encodes 3 Ags: D, C/c, and E/e
CE always together: CE, cE, Ce, ce
D had 2 conditions: D (expressed), d (not expressed)
what % of Caucasians are Rh negative?
15%
what % of Africans are Rh negative?
8%
what % of Asians are Rh negative?
<1%
what happens if a recipient had allo-Abs against particular Ags?
they need Ag negative RBCs
what is a forward test?
patient’s RBC are mixed with a commercial anti-A, anti-B and anti-D
sees which antigens are present on patients RBCs
what is a reverse test?
patients plasma is mixed with commercial testing cells (A+ and B+)
sees which antibodies are in a patients plasma
if anti-A antiserum is mixed with a patient’s RBCs and reacts, what is the patients blood type?
A
patient has A Ag present
if commercial B RBCs react with a patients serum, what is the patients blood type?
A
has anti-B Abs present
requirement for donated RBCs
compatible to recipient plasma
avoid lysis of donor RBCs
requirement for donated granulocytes
compatible to recipient plasma
avoid lysis of donor RBCs
requirement for donated platelets
all ABO acceptable
recipient RBC compatible platelets are preferred
avoid lysis of recipient RBCs by donor plasma
requirement for donated FFP
compatible to recipient RBC
avoid lysis of recipient RBCs by donor plasma
requirement for donated cryoprecipitate
any
small amount, no concerns
function of Ab screen
check whether presence of unexpected non-ABO antibody in the recipients plasma besides anti-A or anti-B
- presence of allo-antibodies
- require prior exposure (transfusion, pregnancy, transplant)
how do you perform an Ab screen
incubate patients serum or plasma with 2 or 3 O testing RBC with known phenotype for most clinically significant antigens
if present anti-RBC, use full panel to identify them
function of identification panel?
do this is Ab screen is + uses group O reagent RBCs -RBCs from 8-20 donors -patient serum or plasma -IS/37/AHG if tubes -AHG only if gel or solid phase reactions documented on a sheet that outlines every RBCs phenotype
if in an urgent situation, what blood products do you give?
O blood- no A or B antigens on RBCs
AB plasma - no anti- A or anti-B in plasma
what is a crossmatch?
mandatory when transfusion is not urgent
confirms ABO compatibility
IS/electronic vs complete XM?
IS/electronic- ABO compatibility only in people w negative Ab screens and no historical Ab (5-15 min)
complete- confirms any incompatibility if there is current/historical Ab present (45 min)
