B3.050 Pre-transfusion Workup

Question 1

what are the 2 steps in a general RBC serological test?

Answer 1

sensitization: Abs binding to RBCs surface Ag
agglutination: sensitized RBCs are bridged together to form the lattice

Question 2

how are serological tests read?

Answer 2

immediately after test is done

visual or by machine

Question 3

what is the function of an antiglobulin test?

Answer 3

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

Question 4

IgM RBC antibodies

Answer 4

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

Question 5

IgG RNC antibodies

Answer 5

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

Question 6

what is phase 1 of the in tube test

Answer 6

immediate spin phase
patients serum mixed with commercial RBCs
mix, centrifuge, examine for agglutination…if positive, there is a present of cold Abs

Question 7

what is phase 2 of the in tube test

Answer 7

37 C incubation to detect warm-reactive Abs

enhancing substances can be added

Question 8

what is phase 3 of the in tube test

Answer 8

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

Question 9

what are the types of antiglobulin tests?

Answer 9

direct antiglobulin test (DAT)

indirect antiglobulin test (IAT)

Question 10

direct antiglobulin test

Answer 10

detects patient’s RBC that have already been sensitized with IgG or complement in vivo (Ab coated RBCs)

Question 11

indirect antiglobulin test

Answer 11

1. detects anti RBC Abs in patient’s serum

2. in-vitro coating of RBCs with antibody or complement

Question 12

gel testing results

Answer 12

positive: agglutination at top of column
negative: unagglutinated cells pass through gel and pellet at bottom

Question 13

solid phase testing results

Answer 13

positive: indicator RBCs diffusely adhere over the well
negative: indicator RBCs pellet to the bottom

Question 14

what are the 2 primary groups of RBC Ags?

Answer 14

oligosaccharide (carb): ABO

amino acid sequence: Rh

Question 15

what are clinically significant allo-Abs?

Answer 15

cause hemolytic transfusion reaction (HTR) and/or hemolytic disease of the fetus and neonate (HDFN)
mostly IgG

Question 16

most important Ag group?

Answer 16

ABO

Question 17

what Ag and Ab does type O blood have

Answer 17

Ag- none

Ab- anti A and anti B

Question 18

what Ag and Ab does type A blood have

Answer 18

Ag- A

Ab- anti B

Question 19

what Ag and Ab does type B blood have

Answer 19

Ag- B

Ab- anti A

Question 20

what Ag and Ab does type AB blood have

Answer 20

Ag- A and B

Ab- none

Question 21

most important protein based RBC Ag?

Answer 21

Rh

Question 22

discuss the Rh genetic possibilities

Answer 22

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)

Question 23

what % of Caucasians are Rh negative?

Answer 23

15%

Question 24

what % of Africans are Rh negative?

Answer 24

8%

Question 25

what % of Asians are Rh negative?

Answer 25

<1%

Question 26

what happens if a recipient had allo-Abs against particular Ags?

Answer 26

they need Ag negative RBCs

Question 27

what is a forward test?

Answer 27

patient’s RBC are mixed with a commercial anti-A, anti-B and anti-D
sees which antigens are present on patients RBCs

Question 28

what is a reverse test?

Answer 28

patients plasma is mixed with commercial testing cells (A+ and B+)
sees which antibodies are in a patients plasma

Question 29

if anti-A antiserum is mixed with a patient’s RBCs and reacts, what is the patients blood type?

Answer 29

A

patient has A Ag present

Question 30

if commercial B RBCs react with a patients serum, what is the patients blood type?

Answer 30

A

has anti-B Abs present

Question 31

requirement for donated RBCs

Answer 31

compatible to recipient plasma

avoid lysis of donor RBCs

Question 32

requirement for donated granulocytes

Answer 32

compatible to recipient plasma

avoid lysis of donor RBCs

Question 33

requirement for donated platelets

Answer 33

all ABO acceptable
recipient RBC compatible platelets are preferred
avoid lysis of recipient RBCs by donor plasma

Question 34

requirement for donated FFP

Answer 34

compatible to recipient RBC

avoid lysis of recipient RBCs by donor plasma

Question 35

requirement for donated cryoprecipitate

Answer 35

any

small amount, no concerns

Question 36

function of Ab screen

Answer 36

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)

Question 37

how do you perform an Ab screen

Answer 37

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

Question 38

function of identification panel?

Answer 38

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

Question 39

if in an urgent situation, what blood products do you give?

Answer 39

O blood- no A or B antigens on RBCs

AB plasma - no anti- A or anti-B in plasma

Question 40

what is a crossmatch?

Answer 40

mandatory when transfusion is not urgent

confirms ABO compatibility

Question 41

IS/electronic vs complete XM?

Answer 41

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)