ABSTRACT
Virtual crossmatch (VXM) compares a transplant candidate’s unacceptable antigens to the HLA typing of the donor before an organ offer is accepted and, in selected cases, supplant a prospective physical crossmatch. However, deceased donor typing can be ambiguous, leading to uncertainty in compatibility prediction. We have developed a web application that utilizes ambiguous HLA molecular typing data to assist in VXM assessments. The application compares a candidate’s listed unacceptable antigens to computed probabilities of all possible two-field donor HLA alleles and UNOS antigens. The VIrtual CrossmaTch for mOleculaR HLA typing (VICTOR) tool can be accessed at http://www.transplanttoolbox.org/victor. We reanalyzed historical VXM cases where a transplant center’s manual interpretation of molecular typing results influenced offer evaluation. We found that VICTOR’s automated interpretation of ambiguous donor molecular typing data would influence VXM decisions. Standardized interpretation of molecular typing data, if applied to the match run, could also change which offers are made. HLA typing ambiguity has been an underappreciated source of immunological risk in organ transplantation. The VICTOR tool can serve as a testbed for development of allocation policies with the aim of decreasing offers refused due to HLA incompatibility.
ABBREVIATIONS
- AFA
- African American
- API
- Asian / Pacific Islander
- ALLAN
- ALLele to ANtigen
- CAU
- Caucasian
- CPRA
- Calculated Panel Reactive Antibodies
- CWD
- Common and Well-Documented Allele List
- DSA
- donor-specific antibodies
- GL String
- Genotype List String
- HIS
- Hispanic
- HLA
- human leukocyte antigen
- HML
- Histoimmunogenetics Markup Language
- IMGT
- International Immunogenetics Project
- IPD
- Immune Polymorphism Database
- KAS
- Kidney Allocation System
- MAC
- Multiple Allele Code
- MFI
- mean fluorescence intensity
- NAM
- Native American
- NMDP
- National Marrow Donor Program
- OPTN
- Organ Procurement and Transplantation Network
- PyPI
- Python Package Index
- SAF
- Standard Analysis File
- SRTR
- Scientific Registry of Transplant Recipients
- UAs
- unacceptable antigens
- UNOS
- United Network for Organ Sharing
- VICTOR
- VIrtual CrossmaTch for mOleculaR typing data
- VXM
- virtual crossmatch