Antibody Detection & Identification

Question 1

When to suspect an antibody?

Answer 1

ABO discrepancy
pos Ab screen
incompatible crossmatch
transfusion reaction
pos DAT
HDFNB

Question 2

screening cells must have what antigens on them

Answer 2

D,C,c,E,e,M,N,S,s,Lea,Leb,Pi,K,k,Fya, fyb, jka, jkb

Question 3

3 cell screening kits must include what antigens?

Answer 3

homozygous Duffy & Kidd antigens

R1R1, R2R2 & rr cells must all be included

Question 4

expiration time frame for all red cell reagents

Answer 4

every 3 weeks

BB labs have standing orders

Question 5

antibody screen limitations

Answer 5

may miss:
low titered antibodies (Kidd)
Ab to low frequency antigens
Ab that do not react under the experimental conditions (pH, LISS, other ions etc)

Question 6

BSA

Answer 6

bovine serum albumin in either 22% or 30%
mechanism is unclear
enhances the sensitivity at AHG phase for most antibodies
requires an increased incubation time!

Question 7

LISS

Answer 7

low ionic strength solution: increases the rate of Ab binding to specific Ag sites on the RBC by decreasing zeta potential
equal volumes of serum & LISS!

Question 8

limitations of LISS

Answer 8

enhances cold autoantibodies & may miss weak Kell Ab

Question 9

PEG

Answer 9

polyethylene glycol: removes water molecules to allow greater chance for collision between antigen & Ab
DO NOT CENTRIFUGE until saline has been added

Question 10

Proteolytic enzymes

Answer 10

papin, ficin, & bromelin
causes breakdown of protein molecules
enhance: Rh, Kidd, Lewis, I, P Ab
denatures: M,N, Fya, Fyb

Question 11

Enhanced methods

Answer 11

ortho gel or immucor capture systems
enhanced sensitivity
automated
objective
cost
pulls up non-clinicially-relevant Ab

Question 12

laboratory information systems

Answer 12

built in systems/checks in place to prevent mistyping, missing antibodies, & other clinically relevant information
always need to confirm all the information on a patient’s file

Question 13

DAT detects:

Answer 13

Ab that have been formed IN VIVO:
autoantibodies
alloantibodies following transfusion

Question 14

DAT reagent

Answer 14

polyspecific AHG for IgG & C3d

if positive, one can go back and test with separate reagents to determine if antibody mediated or complement mediated

Question 15

possible reasons why all 3 cells in a DAT would have various reaction strengths

Answer 15

dosage
multiple antibodies
multiple specificity

Question 16

possible reasons why all 3 cells in a DAT panel are 1+ at IS

Answer 16

IgM antibody to a common antigen

Question 17

antibody ID - autocontrol

Answer 17

Pt plasma is combined with their own 4% RBC solution
includes potentiator
read at all stages

Question 18

IgM antibodies

Answer 18

lewis, Lutheran, M, N, I, & PI

Question 19

IgG antibodies

Answer 19

Rh, Kell, Kidd, Duffy, SsU, Lub

Question 20

antibodies that agglutinate strongly even with heterozygous cells

Answer 20

Ab to K, D,E,e,c,C

Question 21

antibodies that react weakly especially with heterozygous cells

Answer 21

Fya, Fyb, Jka, Jkb, S,s

Question 22

DTT treatment will eliminate which Ab

Answer 22

Kell & Lutheran antibodies

Question 23

what to do when autocontrol is positive

Answer 23

can be caused by cold autoantibody, warm autoantibody or delayed transfusion reaction etc etc
initial investigation should include a DAT
can use elution & absorption techniques to ensure absence of underlying antibodies

Question 24

Cold alloantibodies

Answer 24

Pi, M,N, Lea, Leb
usually insignficiant
prewarming techniques ore neutralization

Question 25

Neutralization of Lewis antibodies

Answer 25

add commercially available lewis antigen to pt plasma & retest - if neg, then Lewis Ab was present & no other Ab are present

Question 26

‘short cold’ panel

Answer 26

select cells that will help ID the suspected cold autoAb
always include a cord cell: I, Le & P neg
most common cold autoantibodies are I, IH & H

Question 27

cold autoabsorption technique

Answer 27

goal: remove the cold autoAb from the plasma so the plasma can be tested for clinically relevant IgG alloantibodies
1. remove plasma
2. treat RBC to remove Ab
3. add plasma back to RBCs
4. incubate at RT so Ab in plasma will bind to RBC
5. remove plasma & test

Question 28

warm autoantibodies

Answer 28

more common than cold autoAb
DAT is pos for IgG
most common warm autoAb is against the e antigen

Question 29

warm autoadsorption limitation

Answer 29

must not perform if patient has been transfused in the last 3 months bc plasma may contain alloAb to transfused cells

Question 30

elution techniques general

Answer 30

performed on pt RBC when the DAT is positive w/ an IgG
goal: ID the Ab bound to RBCs such as in recently transfused patients experiencing reactions & newborn from mother with IgG Ab

Question 31

Elution methods

Answer 31

acid elution: glycine acid is rapid & sensitive. available in kits & used commonly