Blood Compatibility Testing (Crossmatch)

Blood Compatibility Testing (Crossmatch)

A "type" includes a "front type" and a "back type". The "front type" determines which antigens ("flags") in the ABO blood group system are on the patient's red blood cells as follows:

A antigen only	Type A
B antigen only	Type B
A and B antigens	Type AB
Neither A or B	Type O

The "back type" identifies the isohemagglutinin (naturally occurring antibody) in the patient's serum and should correspond to the antigens found on the red blood cells as follows:

anti-B	Type A
anti-A	Type B
anti-A and anti-B	Type O
neither anti-A or anti-B	Type AB

In addition, RBC's are Rh typed and identified as "D" positive or negative.

A "screen" looks for unexpected red cell alloantibodies which may form following pregnancy or prior transfusions. If the screen is positive, the antibody is identified and 2 units lacking the corresponding antigen are crossmatched for the patient. The physician is also notified. Antibody identification can be complicated and take more than a day to complete.

A "type and cross" determines compatibility between patient serum and donor red blood cells.

  A crossmatch is being performed. A full crossmatch procedure takes about 45 minutes to complete and cannot be shortened.

  Units are refrigerated until used. A storage refrigerator is shown here.

  A unit of blood must be properly labelled and the label MUST be checked before use.

source : http://library.med.utah.edu/WebPath/TUTORIAL/BLDBANK/BBPROC.html