Why is it necessary to type and crossmatch blood prior to transfusion?
(with regard to coagulation)

Hi nursekat,

  The simple explanation: A type and crossmatch is necessary to ensure
the recipient has no antibodies to the donor's red cells. It is very
risky to give blood without a crossmatch, although it is done in
extreme emergency, especially where a patient will die without blood.
Antibodies in the recipient can destroy incomatible donor cells after
a transfusion, resulting in serious complications and/or death.

In today?s blood bank, there are typically available the following ?tests?:

Type and Screen:
================
 Checks the patient?s blood group A, B, AB, O and Rh type, pos(+) or
neg(=). (Yes, we use an = sign instead of an ? to prevent clerical
errors).
This allows medical staff to know ahead of time whether the patient
has any unusual antibodies that would delay a crossmatch.


Type and cross(match):
======================
 This is the same as above with the addition of any number of units
(as requested by the physician) of blood to be set aside for an
individual patient. Donor blood is tested with the patient blood to
test for compatibility. This takes about 30 minutes, and is ordered
for patients with a high probability of need.


Type and Hold:
================
  Occasionally a doctor will simply ask for a Type and Hold. In this
case, only the patient?s group and type are done, for the record. This
would be used for a patient who has practically no need for blood.


With regard to coagulation, blood group and type incompatibilities
would result in clotting which would result in hemolysis (a lysing of
red blood cells, releasing cell contents into the bloodstream),  DIC,
hemorrhage, even death.


?If a patient of blood group A (A antigen, antibody B) receives blood
group B (B antigen, antibody A) what happens? The antibody B of the
patient would attack the B antigen of the donor causing them to stick
together. This would block the veins of the patient causing a very
serious condition to the patient which might result in death. The same
would happen if patient blood B receives blood A. Try to work it out.
Therefore blood group A can be given only to persons whose blood is
either A and AB only. On the same lines, blood group B can be given to
persons whose blood group is B and AB.?

?If a patient of blood group O (no antigens, A & B antibodies)
receives blood group B (B antigen, antibody A), B antibodies of the
patient would attack the B antigen of the donor causing the red blood
cells to stick or clog together. On the same principles, if blood
group A were transfused to a blood group O patient, the A antibodies
of the patient would attack A antigens of the donor. Therefore blood
group O patient can receive blood from blood group O donor only.?
http://www.health.gov.mt/nbts/bldgroup.htm

This page has a photo of incompatible blood groups displaying
agglutination (clumping, clotting of red cells).
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/BloodGroups.html

More information here:
http://www.transfusion.ca/new/images/BloodTypeImage.htm

Additional Information
http://w3.uokhsc.edu/pathology/NewsltrJrnl/transtribune/tt00mar.PDF

http://www.diaglab.vet.cornell.edu/clinpath/modules/coags/xmatch.htm

I hope this has helped you out! Please request an Answer
Clarification, before rating, if anything is unclear. This will allow
me to assist you further, if possible.

Sincerely, Crabcakes

Search Terms
ABO Rh
Agglutination
Blood Banking experience

Actually, the absolute risk of transfusing uncrossmatched blood is
relatively small.  Crossmatching obviously reduces it even more, but
the transfusion of uncrossmatched blood (even O+ or O- blood into
patients who have not yet had the type and screen done) is not that
uncommon in emergency situations (gun-shot or stab wounds, blunt
trauma with signs of shock, ruptured ectopic pregnancy, to name a
few).

The following quote is from Miller's Anesthesia, 6th edition (2005,
Elsevier).  It gives an idea of the risks involved:

"Is the Crossmatch Really Needed?
In previously transfused or pregnant patients, only about 1 patient in
100 may have an irregular antibody other than the anti-A and anti-B
antibodies. However, some of these irregular antibodies are reactive
only at temperatures below 30°C and therefore are insignificant in
most transfusions. Others that are reactive at about 30°C can produce
serious reactions if the transfused cells contain appropriate antigen.
In order of probable significance, anti-Rh(D), Kell, C, E, and Kidd
are the most common of clinically significant antibodies. After anti-A
and anti-B, anti-Rh(D) is the most common significant antibody. If the
correct ABO and Rh blood type is given, the possibility of transfusing
incompatible blood is less than 1 chance in 1000. Put in other terms,
ABO-Rh typing alone results in a 99.8% chance of a compatible
transfusion, the addition of an antibody screen increases the safety
to 99.94%, and a crossmatch increases this to 99.95%.[44]

The blood bank can reduce the chance of incompatibility by performing
an antibody screen. The chance of this screening test's missing an
antibody that is potentially dangerous has been estimated to be no
more than 1 in 10,000.