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.
