What is a virtual crossmatch?

A virtual crossmatch is a computer-based test that predicts whether a donor and recipient are compatible. It compares the donor’s tissue type (HLA) with the recipient’s “unacceptable antigens,” which are markers the recipient’s immune system would likely reject because of existing antibodies.

This computer screening helps registries quickly search large national databases for potential matches. While it is a very useful first step, a physical laboratory test is usually performed to confirm the match before surgery.

Which tests are required for a virtual crossmatch?

To perform a virtual crossmatch, registries need detailed genetic and immune system information from both the donor and the recipient:

• Donor HLA Typing: Donors must be typed for specific human leukocyte antigens (HLA). At a minimum, this includes HLAA, B, C, DR, and DQ. Many national registries also require typing for DRB3/4/5, DQA1, DPA1, and DPB1. Highresolution HLA typing enables more precise epitope matching, increases the likelihood of a suitable match, and helps identify crossreactive HLA antibodies.

• Recipient Antibody Profile: The recipient’s blood is tested to identify “unacceptable antigens”—the specific HLA markers their immune system would likely reject.

• Single Antigen Bead Assays: This sensitive technology measures the Mean Fluorescent Intensity (MFI) of the recipient’s antibodies. It helps determine which donor HLA types should be considered unacceptable. The computer then compares donor and recipient data to predict compatibility, even if they are not in the same location.