Crossmatch also known as compatibility testing, pretransfusion testing or typing. The
definition of a compatibility test is a series of procedures use to give an indication of blood group compatibility between the donor and the recipient and to detect irregular antibodies in the recipient's serum.
The main purpose for performing a crossmatch is to promote the safe transfusion of blood.
We are performing testing to demonstrate donor blood is compatible with recipient's blood.
Crossmatch procedures should be designed for speed and accuracy - get the safest blood reasonably possible available to patient as soon as possible. The goal of compatibility test is:
Detect as many clinically significant antibodies as possible
Detect as few clinically insignificant antibodies as possible
Complete the procedure in a timely manner.
Once donor blood is crossmatched with a potential recipient, the results of crossmatch is good only 3 days. If the physician wants the donor blood available longer, we must get a new recipient sample and repeat tests. This protocol helps detect new antibodies that may be forming, especially when patient has been transfused within past three months.
Parts of the Crossmatch
Identification of recipient and recipient blood sample is crucial since major of the hemolytic transfusion reactions are due to errors in patient or sample identification.
ABO and Rh typing of recipient's blood and resolving any ABO discrepancies. If the discrepancy cannot be resolved before patient needs transfusion type O blood should be given. If problems arise with D testing, Rh negative blood should be given.
Performing an antibody screen on recipient's serum for clinically significant antibodies.
These antibodies are most likely to occur in 37oC and AGT phases of testing. Each negative AGT test must be followed by "Coombs Control Check Cells." An
autocontrol may or may not be used. Some labs prefer to perform this routinely during the antibody screen while others will only include it if an antibody needs to be identified. The autocontrol has to be part of antibody identification procedure.
Comparing present findings with previous records for the recipient. If previous testing has been performed on the recipient and should match current testing. These
comparisons can give assurance that no identification errors have occurred, but it is not proof. Records would also show if clinically significant antibodies have been
detected in the past. These antibodies may be presently at undetectable levels. Any history of clinically significant antibodies, even if undetectable now in the patient, dictates an antiglobulin phase crossmatch needs to be done between recipient's serum and donor's cells.
Confirmation of ABO and Rh type of red cell components being given when of blood is received in laboratory.
Selection of appropriate ABO and Rh component units for the recipient first would be the same ABO and Rh type. Transfused donor red cells must be ABO compatible with the patient's plasma and whatever antibodies may be present. Transfused plasma must be ABO compatible with the recipient's red cells.
Selection of Components When ABO-Identical Donors Are Not Available ABO Requirements
Whole Blood Must be identical to that of the recipient Red Blood Cells
(most plasma removed) Must be compatible with the recipient's plasma.
Granulocytes, Pheresis Must be compatible with the recipient's plasma.
Fresh Frozen Plasma Must be compatible with the patient's red cells.
Platelets, Pheresis All blood groups acceptable; components
compatible with the recipient's red cells preferred Cryoprecipitated AHF All ABO groups acceptable
Rh-positive components should be given to Rh-positive individuals and Rh-negative units should be reserved for D-negative individuals. The physician needs to be
involved in decisions relating to giving Rh-positive blood to an Rh-negative individuals since those individuals have 80% chance of making an anti-D following transfusion.
Perform a crossmatch either serologically. If no clinically significant antibodies are found in the recipient the institution has the option of choosing an immediate-spin crossmatch (serologic technique) or a computer crossmatch. If clinically significant antibodies are found, an antiglobulin crossmatch must be performed.
Type and Screen
The type and screen consists of ABO/Rh, antibody screen, and a records check. This order is used when likelihood of needing blood is low. Therefore, no donor blood crossmatched to patient. If need for blood suddenly arises, you can take sample that is already typed and screened, and perform a crossmatch with donor units from the specimen. Type and screen protocol cannot be used if patient has an antibody. Then an antiglobulin crossmatch must be performed.
Benefits of a Crossmatch
Performing a crossmatch before transfusing blood has the following benefits:
Detects major ABO errors (ie. crossmatching an A donor with an O or B recipient )
Detects most recipient antibodies to antigens on donor red cells (if the antibody is in high enough titer to react) One of the most common clinically significant antibodies that are missed are the Kidd antibodies.
Limitations of a Crossmatch:
Will not detect errors in patient identification (unless a previous record exists)
Will not detect ABO mix-ups if blood types are compatible (can crossmatch group A donor blood for an AB recipient)
Will not detect Rh errors (can crossmatch Rh+ donor blood with Rh negative recipient with no reaction if the patient has no anti-D)
Will not detect all recipient antibodies to donor antigens (antibody may be too weak to detect, but still cause transfusion reaction such as the Kidd antibodies)
Will not prevent alloimmunization of recipient (only ABO and Rh antigens matched - patient can potentially make antibody to all the other antigens) This is why many of the discovered antibodies are found in multi-transfused patients.
Immediate Spin versus Antiglobulin, Coombs, Crossmatch
The purpose of Immediate spin step of crossmatch is to detect major ABO incompatibility between donor and recipient. ABO incompatibility is the most common life-threatening type of transfusion reaction and is often due to clerical errors.
It is permissible to stop at immediate spin step of crossmatch if:
1. Immediate spin is negative and
2. Antibody screen is negative in all phases and 3. There is no record of previous antibodies
It is NOT permissible to stop at the immediate spin step and must carry crossmatch through antiglobulin, Coombs, phase if:
Immediate Spin test agglutinated or
Patient has an antibody (screening cells are positive) or
Patient has a record of a previous antibody