Testing for sensitization to HLA (or Antibody screening)

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  • Crossmatch Testing: This test is done once the donor kidney is available. Presence of antibodies in the recipient’s blood against the donor HLA can cause rejection of donor kidney. These preformed antibodies (anti-HLA antibodies) may be produced due to sensitization (allergy), caused by exposure of recipient to foreign HLA (other persons) during a previous blood transfusion, pregnancy or a transplant. Hence anti-HLA antibodies are detected in the recipient’s blood to predict the risk of rejection of donor kidney.

The recipients blood is mixed with the donor’s blood. If there is  there is a reaction i.e. antibodies are present against donor HLA  it is called a positive crossmatch. This means that the recipient is “incompatible” with the donor (i.e. the donors kidney is not right for the recipient). However, if there is no reaction i.e. antibodies are absent it is called negative crossmatch. This means that the recipient is “compatible” with the donor (i.e. the donor’s kidney can be given to the recipient).

Panel reactive antibody: Sometimes highly sensitive recipients may react against most of the donor HLAs. This test is done by mixing a small amount of recipients blood with an equal amount of cells (bearing the HLA) from 60 different people, in separate tests. This test can therefore help in finding how many different HLA antibodies are present in the recipients blood. Hence, while selecting the appropriate donor all those donors (against whose antigen, the antibodies are present in recipient blood) can be easily avoided. Because the antibody status can change from time to time it is imperative to perform this antibody screening regularly, usually on a monthly basis.