IMPLEMENTATION OF THE VIRTUAL CROSSMATCH (VXM) IN AUSTRALIA FOR DECEASED DONORS AND KIDNEY TRANSPLANT WAITLIST RECIPIENTS
Ms NARELLE WATSON1, Ms Rebecca Scammell1, Ms Natasha Haywood1, Ms Rhonda Holdsworth2, Assoc Professor Ross Francis3
1Transplantation and Immunogenetics Lifeblood, Sydney, Australia, 2Transplantation and Immunogenetics Lifeblood, Melbourne , Australia, 3Princess Alexandra Hospital, Brisbane , Australia
Background: For over 40 years, Complement Dependent Cytotoxicity (CDC) crossmatching, was the final test used for assessment of compatibility of kidney donors kidney and a potential transplant recipient. Due to limited reagent supply, national phase-out began in 2022, fully transitioning to virtual crossmatching (VXM) by 2023.
Method: VXM utilises the assignment of patients Unacceptable (UA) HLA antigens, based on HLA antibodies (HLA-Ab)>2000/4000MFI, and the Kidney Matching algorithm in OrganMatch to enable compatible patients to offered kidneys. Final assignment of donor specific HLA-Ab (DSA) using Luminex Single Antigen Bead HLA-Ab tested within 3 months. A retrospective Flow crossmatch (FXM) is available for highly sensitised patients or urgent cases.
Aim: Review of 12 month period, from 1st January 2023 to assess results and adverse events associated to the change in testing practise.
Results: Of 772 patients transplanted, 67.9% were unsensitised and 32.1% sensitised (13.6% mPRA 1-50%, 4.9% mPRA 50-80%, 3.9% mPRA 80-95%, 4.1% mPRA 95-98%, and 5.6% 99-100%. 54/772 patients transplanted across DSA on current sera, 22 FXM performed, only 6 FXM positive results (patient 1 HLA-C*08:01 (MFI 4122) FXM T-B+, patient 2 HLA A*26:01 (MFI 2618) T+B+ FXM, patient 3 HLA DRB1*10:01 (MFI 1591) FXM T-B+, patient 4 HLA B*08:01/C*07:02 (MFI 3871/4191) FXM T-B+. patient 5 HLA DRB1*07:01 (MFI 1818) FXM T-B+ ,patient 6 HLA*DRB1*12:02/DRB1*12/B*44:03/B*44:02 (MFI 2987/2487/2734/1527) FXM T-B+. In 2023, 96/1275 kidney offers were declined by the due to DSA , compared to 119 in 2022. There was one graft loss due to renal artery thrombosis reported.
Conclusion: Confidence in the new process is evident through low decline rates and flow crossmatch requests, showing acceptance in the HLA antibody screening, DSA assignment and VXM.
Presentation Slides PDF – Click here
Biography:
Clinical Scientist with over 35 years experience in Histocompatibility testing and Immunogenetics, previous experience includes Lab Manager of NSW Transplantation and Immunogenetics laboratory , Masters of Applied science , and admitted to the RCPA Faculty of Science. Currently the National OrganMatch Manager, member of TSANZ Virtual crossmatch committee