ABO DISCREPANCIES
Jean Purcelli, MT(ASCP)SBB
Blood Centers of the Pacific
• ABO discrepancies occur because of:
• Intrinsic problems with the red cells or the
serum.
• Test related problems—slide vs. tube
• Technical errors.
Intrinsic red cell problems
• Weaker subgroups of A and B or AB such as A2,
Ax, A3, A2B and subgroups of B.
• Variant A or B genes such as B(A). Must be
differentiated from a subgroup of AB.
• A patient who has had a bone marrow transplant
or an A or B recipient recently transfused with
group O red cells.
Intrinsic
problems
Intrinsic red
red cell
cell problems
• Acquired
with
infections
AcquiredB.B.Usually
Usuallyassociated
associated
with
infections
from
from GI
GI(gastro-intestinal)
(gastro-intestinal)bacteria
bacteria
• Polyagglutinable state. The red cells are
• Polyagglutinable
state. The
cellssource
are antiunexpectedly agglutinated
by red
human
unexpectedly
agglutinated
by human source
A and Anti-B. Not
seen with monoclonal
antisera.
anti-A and Anti-B. Not seen with monoclonal
antisera.
• Potent cold agglutinins
Intrinsic problems in the serum
Anti- A or –B is not usually detectable until 4-6 months of
age. Any reactivity is usually maternal IgG forms of anti-A
or –B.
A2 or weaker subgroups of A or AB may produce anti-A1.
Anti-A1 will react with A1 cells but not A2 or O cells.
Allo-antibodies such as anti-M,-N,-P1, Lea or Leb
May react at IS (immidiate spin)or RT(room temperature)
and react with the A or B cells.
Intrinsic problems with the serum
• Abnormal concentrations of proteins or
infusion with high molecular weight plasma
expanders may show aggregation that is
difficult to distinguish from true agglutination.
• Immunodeficient patient, due to disease or
therapy may have decreased levels of anti-A
or –B.
Intrinsic problems with the serum
• Infusion of large volumes of compatible but not
type specific plasma.
• Bone marrow transplants with compatible but
dissimilar ABO groups. Example: a group A
individual who receives group O marrow will
produce circulating O cells, but produce only antiB in the serum.
• Potent cold aggutinins.
ABO
seenwith
withtest
test
ABOdiscrepancies
discrepancies seen
related problems
problems
related
• Abnormal proteins, infusion of
macromolecular solutions or improperly
collected cord blood (contaminated with
Wharton’s jelly) may cause false agglutination
of cells. This is especially true when the cells
are resuspended in serum which is usual for
slide typing.
Problems with the test system
•Serum
• Serummay
maycontain
containantibodies
antibodiestotothe
thedyes
dyesused
toused
colorto
anti-A
anti-B
give
colorand
anti-A
and (USA)
anti-Bwhich
(USA)may
which
false
with
serum-suspended
maypositives
give false
positives
with serum-cells in the
slide
test.
suspended
cells in the slide test.
Resolving AB0 discrepancies
• Repeat the tests after washing patient cells
and the A and B cells several times.
• Analyze the problem:
1. Unexptected
Unexptected ++ororunexpected
unexpected––results?
results?
2. Whatisisunusual
2.What
unusualorordifferent?
different?
3. Doyou
3.Do
yousee
seespontaneous
spontaneousagglutination?
agglutination?
Resolving ABO discrepancies
• If the serum is unexpectedly positive, does the
agglutination look like rouleaux? Use salinereplacement technique.
• Should you try to prove anti-A1 in an A2
person. Type patient cells with anti-A1 lectin.
• Test the serum with screening cells, and
another set of A1 and A2 cells.
Resolving ABO dicrepancies
• Is there strong hemolysis in reverse grouping
tubes?
tubes? Add
Add another
another drop
drop of
of appropriate
appropriate cell
cell
and
and centrifuge
centrifuge again.
again.
•
•
•
•
Is the serum typing unexpectedly negative?
Is the serum typing unexpectedly negative?
Add several more drops of serum to all reverse
Add
several
more
drops ofthe
serum
to all reverse
grouping
tubes,
incuding
3 O screening
grouping
tubes,
3 O screening
cells and an
autoincuding
control. the
Incubate
at RT or
cells
and an auto control. Incubate at RT or
colder.
colder.
Resolving ABO discrepancies
• If the discrepancy cannot be resolved , a
patient should be transfused with group O red
cells of the appropriate Rh type.
• A donor units may not be labelled or released
for transfusion and should be discarded.
• Refer to examples of paper ABO discrepancies
• And serological resolution