The omission of the “wet” pre‐transplant crossmatch in renal transplant centres in Scotland

Abstract

The methods used for assessment of immunological risk for a patient receiving a kidney from a deceased donor have undergone significant change in the last few years. Many centres now proceed to transplant without any additional laboratory‐based HLA testing for patients who are well defined as HLA antibody negative. Using rapid HLA antibody tests at the time of donor offer, such as Luminex, it is also possible to omit wet crossmatches in many sensitised patients. This virtual crossmatch (vXM) approach provides benefits in reducing cold ischaemia time (CIT), but also carries risks such as missing clinically relevant non‐HLA reactivity or allelic HLA antibody reactivity. A number of factors need to be in place in a laboratory to enable a vXM policy to be extended to both sensitised and non‐sensitised patients including access to complete donor HLA typing, ability to undertake Luminex‐based HLA antibody testing out of working hours, and access to senior H&I Scientist expertise to assess and interpret results. Other approaches, such as using peripheral blood lymphocytes for crossmatching, may also enable a reduction in CIT and transplant units need to assess the risks of extending vXM processes for their patients against potential benefits.

Out with the old, in with the new: Virtual versus physical crossmatching in the modern era

“…Studies have shown that VXM and FCXM have similar accuracy, specificity, and sensitivity in detecting DSA . Therefore, many programs worldwide have adopted the VXM as the only assessment performed prior to transplantation for selected candidates . We have recently published our VXM data both pre‐ and post‐KAS implementation .…”

“…30 Therefore, many programs worldwide have adopted the VXM as the only assessment performed prior to transplantation for selected candidates. [31][32][33][34][35][36] We have recently published our VXM data both pre-and post-KAS implementation. 37 During the first 9 months post-KAS, 129 deceased donor transplants were performed wherein 43 (33.3%) were candidates with CPRA of 99% to 100%.…”

BSHI/BTS guidance on crossmatching before deceased donor kidney transplantation

“…In these early publications, the recipient groups were carefully defined with the majority being males with no sensitizing events and negative for HLA-specific antibodies. Other centres adopted VXM policies and there are many publications in the literature across the world detailing different approaches to this in order to minimize CIT (Jani et al, 2017;Rohan et al, 2020;Turner et al, 2019). The work from Taylor et al (2000) suggests a saving in CIT of at least 3 h is achievable if a VXM is used instead of a crossmatch requiring donor leucocytes, and this was also associated with a reduced incidence of delayed graft function.…”

Generation of Unexpected Allele-Specific Anti-HLA Antibodies after the Transplantation of a Fully-Matched Kidney Allograft and the Diagnostic Approaches Required for Excluding Harmful Effects after Subsequent Renal Regrafts

“…Although the idea of implementing virtual crossmatching as a complete replacement for de facto crossmatching had been put forward more than 20 years ago, the wider acceptance of this approach has been accompanied by the progress of Luminex-based techniques, which have increased the resolution up to the level of single-antigen beads (SAB); thus, providing the required number of immobilized single antigen analytes. Although the transplantation programs in some countries use virtual crossmatching as the only evaluation method before allografting for certain groups of recipients, the Eurotransplant community currently performs de facto crossmatching as the last assessment before grafting [11][12][13]. However, the initial selection of offered kidneys is based on the virtual crossmatching procedure by determining unacceptable antigens to exclude prospective recipients who exhibit the corresponding antibodies.…”