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Virtual and Reality: An Analysis of the UCLA Virtual Crossmatch Exchanges
Arlene F Locke1, Michelle Hickey, Nicole M Valenzuela
1UCLA Immunogenetics Center, Department of Pathology and Laboratory Medicine, UCLA Health, Los Angeles, CA.
Transplantation
|March 22, 2023
Summary
The virtual crossmatch (VXM) shows high agreement with flow crossmatch (FXM), but variability exists with certain antibody levels and specificities. Standardization and exchange surveys are crucial for improving VXM accuracy in organ transplantation.
Area of Science:
- Immunology
- Transplantation Science
- Clinical Laboratory Science
Background:
- The virtual crossmatch (VXM) is vital for predicting organ donor-recipient compatibility.
- Nonstandardized laboratory practices introduce variability in VXM interpretation, particularly with human leukocyte antigen donor-specific antibodies (HLA DSA).
Purpose of the Study:
- To assess factors influencing VXM prediction variability in the presence of HLA DSA.
- To evaluate laboratory concordance for VXM and flow crossmatch (FXM) through a VXM Exchange survey.
Main Methods:
- UCLA's VXM Exchange survey involved 35 laboratories testing 36 donor samples and 72 HLA reference sera from 2014-2019.
- Laboratories performed HLA antibody testing, FXM, and VXM, generating 144 T/B-cell FXM pairs and 112 T/B-cell VXM pairs.
Main Results:
- High concordance was observed in FXM (86% T-cell, 84% B-cell) and VXM (81% T-cell, 80% B-cell) surveys (>80% concordance).
- FXM and VXM concordance was 79% for T-cell and 87% for B-cell.
- Variability in VXM was noted with high-titer antibodies (prozone effect), weak-to-moderate DSA, and DSA against low-expression antigens.
Conclusions:
- VXM and FXM show high consensus, especially with strong DSA.
- Standardization and continuous learning through exchange surveys are essential to enhance VXM accuracy and quality control across laboratories.
- Addressing variability in specific antibody scenarios will improve VXM reliability in organ transplantation.
