P060 Next generation virtual crossmatch: A program that captures data and provides rapid and accurate virtual crossmatch assessments

Abstract

Aim To test the benefits of a software tool that captures HLA antibody analyses, highlights DSA and other risk factors, and provides a comprehensive report to allow fast and accurate Virtual Crossmatches (VXMs). Methods The VXM program used embedded, tiered reviewed HLA antibody data obtained from phenotype and single antigen bead panels. HLA antibody assignments in the VXM program required 2 independent reviewers and were not based on a MFI threshold; rather, assessments included HLA reactivity patterns, confirmation on multiple assays or in multiple sera, and previous HLA exposures (pregnancies and transplants). HLA typing for each potential donor was entered and DSA specificities, if present, were highlighted with individual strength assessments. Embedded HLA typing results for each candidate and all previous allografts allowed reporting of repeated HLA mismatches. Additional alerts included recent HLA sensitization changes, dates for peak and last serum tested, and HLA allele-specific antibodies that cannot be listed as avoids. Results A comparison was performed using results from the VXM program and 251 manual VXMs performed by experienced laboratory personnel during the first quarter of 2017. The majority (82%) of these VXMs involved sensitized candidates and >50% involved 99–100% CPRA candidates. One hundred of 251 VXMs examined were limited to one assessment per patient, but for the majority of cases VXM HLA analyses were performed repeatedly for the same patient. In 7.5% of manual VXMs cases, a secondary review of HLA data improved final DSA assignments. The number of VXMs per donor ranged from 1 to 6 with an average of 1.5 patients per donor. The average time for a manual VXM per patient was 30 min, while the VXM program and embedded data required 5 min per patient. In addition, the VXM program stored all previous donor assessments to assist in the decision to accept or decline the current offer. Conclusions For centers that do not list all HLA antibodies as unacceptable for sensitized waitlist candidates, VXMs can present a complex challenge given that potential donors must be reviewed and accepted/declined within one hour of initial offer. A VXM program that uses tiered reviewed HLA data increases efficiency and reduces possible errors in assessing risk for highly sensitized candidates.