Status quo of histocompatibility testing and prospects for virtual crossmatching within the Korean kidney allocation system: survey of laboratory directors

The Korean kidney allocation system (KAS) currently imposes disparities for highly sensitized candidates because it does not account for human leukocyte antigen (HLA) antibody-defined unacceptable antigens. Virtual crossmatch (VXM) may provide a solution by enhancing histocompatibility assessment and improving the efficiency of the overall allocation process. This study surveyed Korean HLA laboratory directors to evaluate current practices, opinions on VXM, and prerequisites for its implementation. An electronic survey addressing HLA typing, HLA antibody testing, and VXM concepts was distributed to 48 histocompatibility laboratory directors in September 2024. Responses were received from 31 institutions (64.6% response rate), representing 72.9% of deceased donor kidney transplants performed in Korea in 2024. All responding institutions conducted HLA typing and physical crossmatch (PXM). Only 61.3% performed single antigen bead assays in-house, and 77.4% reported donor HLA typing at the two-digit serological level. A strong consensus (88.9%) defined highly sensitized candidates as those with calculated panel-reactive antibody >80%, with 66.7% supporting their prioritization. All participants (100%) recognized "improved process efficiency by excluding highly sensitized patients with presumed PXM positivity from the allocation process" (44.3%) as the greatest benefit of implementing VXM, although mean fluorescence intensity cutoffs and testing intervals varied by institution. Korean HLA laboratory directors broadly support the concept and need for VXM, acknowledging its potential to improve both efficiency and equity for sensitized patients. However, the lack of standardization in HLA testing application and interpretation remains a significant practical challenge. National initiatives and multidisciplinary collaboration are essential before integrating VXM into the Korean KAS.