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Clinical Pathology Laboratory - Available Test
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Crossmatch
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| A crossmatch is performed prior to administration of blood or blood
products (e.g. packed red blood cells). The purpose of the crossmatch
is to detect the presence of antibodies in the recipient against the
red blood cells of the donor. These antibodies attach to the red blood
cells of the donor after transfusion. An incompatible transfusion
can result in a severe hemolytic anemia and even death. In dogs and
horses, naturally occurring antibody against important hemolytic red
blood cell antigens (e.g. DEA 1.1 and 1.2 in the dog, and Qa and Aa
in the horse) are not found. Therefore, these animals require sensitization
to the red cell antigen, before a hemolytic reaction will occur. This
sensitization usually occurs from a previous blood transfusion. Therefore,
in these species, a crossmatch does not need to be performed on the
first blood transfusion (as long as you are sure this is the first
transfusion). Once a blood transfusion has been administered to a
dog or horse, a crossmatch should be performed prior to any subsequent
transfusions to detect antibodies that may have been produced against
a different red blood cell antigen. In cats, a crossmatch should be
performed on the first blood transfusion, because cats have naturally
occurring antibody to red blood cell antigens. In type B cats, the
anti-A antibody is a strong agglutinin and hemolysin and can result
in rapid hemolytic anemia and death if a B cat is transfused with
A blood on the first transfusion. Type B cats are uncommon amongst
DSH, but are found in higher frequency amongst the exotic breeds,
e.g. Somali, Devon Rex. For more information on blood groups and transfusion
reactions, please refer to the Transfusion Medicine portion of our
Hemostasis Module. |
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| For a crossmatch procedure, we do 3 types of crossmatches: |
Major crossmatch: This is the most important one. In this
procedure, we are looking for antibodies in the recipient against
transfused red blood cell antigens (from the donor). Therefore,
we need serum from the recipient and red blood cells from the
donor.
Minor crossmatch: This detects antibodies in the donor
serum to the recipient's red blood cells. Therefore, for this
we need serum from the donor and red blood cells from the recipient.
Autocontrol: We also perform an auto-control with our crossmatches,
i.e. recipient serum with recipient red blood cells.
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| In these procedures, washed red blood cells are incubated with serum
at 37 C (e.g. for the major crossmatch, washed donor red blood cells
are incubated with recipient serum). We then look for agglutination
microscopically. In horses, we add complement (to enhance hemolysis)
and look for both microscopic agglutination and grossly visible hemolysis.
In horses, we also perform the test at 2 dilutions, 1:4 and 1:16.
The report below is from one of our crossmatches (this was actually
done in a horse). |
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| We use the following guidelines for interpretation of the crossmatch: |
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Crossmatch
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Result
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Interpretation
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Major
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Compatible
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The transfusion can be given. Note that the crossmatch will
not detect very low titer antibodies. |
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Agglutinins and/or hemolysins
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The crossmatch is incompatible and the donor should not
be used* |
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Minor
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Compatible
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The transfusion can be given |
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Agglutinins and/or hemolysins
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Preferably, washed or packed red cells from the donor should
be administered. In reality, dilution of the transfusion in
the recipient usually eliminates any likelihood of antibodies
from the donor affecting the recipient's red cells. |
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Autocontrol
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Agglutinins and/or hemolysins |
This reaction is usually seen in animals with immune-mediated
hemolytic anemia. In these, interpretation of incompatible crossmatches
is very difficult and a compatible donor may not be found. |
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In horses, an incompatible crossmatch with a titer > 1:16 should
not be administered. A weak incompatible reaction (titer <1:16)
may be due to anti-Ca antibodies, which will not result in a hemolytic
reaction. However, the titer at which hemolysis may be expected has
only been established for anti-Aa and anti-Qa antibodies. Although
these are the most common red cell antigens that cause transfusion
reaction in horses, reactions to other red cell antigens (e.g. Pa)
have been reported. The titer at which these antibodies are likely
to produce a reaction is not known. For this reason, unless the blood
type of the donor and recipient horse are known, we recommend that
a crossmatch with a weak positive titer should not be administered. |
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