Opening
The 2026 extramural meeting was opened by Nils Lachmann (Charité, Berlin).
Following the opening, Yvonne Zoet (ETRL) announced the new ETRL director. From 1st of June onwards, Gottfried Fischer will be the ETRL director. He will stay for two years.
External proficiency testing
Yvonne continued with the external proficiency testing (EPT) results of 2025. For HLA typing, a discrepancy rate of 1.8 % was observed. For cross-matching (all results included) discrepancy rates were 3.5 % for donor centers and 2.3% for recipient centers, both within the normal range.
To complete the overview, data from screening detection and screening identification scheme were also shown. In screening detection, discrepancy rates were 1.0% for HLA class I antibodies, and 4.6 % for HLA class II antibodies. For screening identification scheme, CDC and SPA Single Antigen techniques were assessed. In CDC, 13 consensus specificities were found and in SPA SA 468 consensus specificities were found. For SPA SA Complement Fixing antibodies 71 consensus specificities were found. Finally, Yvonne showed the change in shipment of sera. Sera will both be used for crossmatching and detection and identification of antibodies. The ETRL decided together with the TTAC to have a combination with interpretation of results for now.
This led to a discussion whether in EPT results are solely assessed on their technical aspects or in combination with interpretation. Many laboratories use for CDC crossmatching and for CDC identification of antibodies results obtained from Luminex single antigen techniques to assign specificities. The ETRL will explore ways to divide assessment for the technical part of the results and the interpretational part.
The next topic on the agenda was the discussion of the three patient-based cases of 2025, also presented by Yvonne Zoet. A summary of the results of each case is published on the EPT website.The first case was about a male with cytotoxic antibodies against HLA-A2, B17 and B12, which declined over time. No Class II antibodies were detected. He had a luminex antibody against B*15:12 (MFI 15.000) , which is also part of the ambiguous donor-HLA-type (B*15:01/12/14).
A small majority considered the donor to be suitable as B*15:01 (B62) was the most likely typing, where the other part of the participants considered that this ambiguity should be solved before transplantation. In reality this was an older case, from a time when luminex single antigen test were not routinely performed. The patient was transplanted and needed re-transplantation 21 years later.
The second case was about a female patient with DPB1*02:01 reactivity. Her own HLA type included DPB1*02:01P, which probably was a DPB1*678:01 (deduced from the HLA-type of one of her children). The donor was typed DPB1*02:01 and crossmatches were negative. About 66% of the participants considered the kidney donor suitable, because of negative crossmatch next to patient and donor being DP-sero-type identical. The patient was not transplanted with this kidney as the clinicians had difficulties in risk estimation of this transplantation.
The last case involved a female donor, diagnosed with SLE. Crossmatches on spleen cells reacted as expected including all controls. For crossmatches in blood in two centers an aberrant pattern was seen, with negative controls that turned positive. This could be caused by medication given to the donor to treat the disease or because of the underlying disease.
Yvonne ended her presentation with a request to all tissue typing centers to send in new cases to etrl@eurotransplant.org.
Improvement in ETKAS point system (vPRA-sliding scale, B-DR matching and matchability)
The next speaker was Hans de Ferrante, who showed how simulation data can be useful to guide changes to the kidney allocation system. He explained the current ETKAS point system that dates back to 1996. This point system includes the mismatch probability (MMP) points. He proposed to replace MMP by a vPRA sliding scale and matchability, to make the allocation fairer for immunized patients and patients with difficult-to-match HLA, including homozygote patients.
A next possible adaptation of the ETKAS point system is the introduction of age matching in combination with B-DR matching. Further simulations are necessary to overcome over-compensation of young recipients.
News from the TTAC
After lunch the meeting continued with Nils Lachmann, who presented the topics discussed during the TTAC meeting held on the 19th of March 2026, in Brussels, Belgium.
Cynthia Kramer stepped down as secretary of the TTAC, Gonca Karahan stepped down as chair of the TTAC and Blanka Vidan-Jeras stepped down as representative for Slovenia. Nils thanked them for their contributions.
Eric Spierings asked whether Gottfried Fischer in his new function will continue to be a representative from Austria. Gottfried Fischer will stay in the TTAC representing the ETRL. From Austria a new representative will be appointed.
The following points were discussed in the TTAC meeting:
- P-TTAC01.25 Use of allele-specific unacceptable data within AM program
Status: Pending Implementation. The policy is approved by the TTAC and ET is working on its implementation.
- R-TTAC01.22 Inclusion criteria AM program: The AM program inclusion criteria needed some adjustments in defining the “hard to transplant” patients and compensation for different waiting times in ETKAS and AM
Status: Pending Decision
- P-TTAC02.25 Omission and retrospective decisive crossmatch
Status: Ongoing discussion. Further discussions and policy drafting.
- Desensitization within AM. This should be done separately from the AM program.
- EPT topics (FCXM, extended SAB panels, new HLA antibody detection kits)
- Discussion on relevance of CDC as AM inclusion criterium
- Joint working group with ETKAC on replacement of mismatch probability in ETKAS
- HLA mismatch profile Incident in ESP
- Joint Project by ET, ETRL, EThAC and TTAC: iTHOR Thoracic transplantation for immunized patients in Eurotransplant
- Open working groups on three topics with high IT demands:
- 1. Electronic submission of recipient HLA typing to ENISNext
- 2. Upload of high-resolution donor HLA typing using ONT
- 3. Update of pre-filter and HLA table.
For further details on all subjects, please see the presentation of Nils Lachmann on the ETRL website.
Advancements in HLA-typing
The program then continued with Gottfried Fischer, who discussed advancements in donor HLA typing. He described donor typing as a critical bottleneck in the virtual crossmatch process since, unlike antibody analysis, it cannot be repeated or optimised once the deceased donor workflow has begun. He presented an analysis of HLA typing errors from 2024 to 2025 and noted that 33 out of 4,376 donors (0.75%) were incorrectly matched, equating to one in every 133 donors. In 16 cases, the typing contained incorrect or missing alleles compared to the confirmatory results, and in 15 cases, there were extra alleles. These errors affected all 11 loci, with HLA-C, -DRB4, -DQB1 and -DPB1 being the most frequently affected.
In five of these cases, a DRB4*01:03N null allele was erroneously reported as an expressed DR53 allele.In two cases, the typing of a different individual was uploaded, representing the most severe error category.
Gottfried proposed corrective actions, including local confirmation typing; a defined re-typing policy at the recipient center; automated plausibility checks using the donor’s date of birth in the HLA string; a risk assessment framework within the TTAC; and a revision of Chapter 10 of the ET Manual. In the medium term, he recommended using ONT sequencing and the HATS tool to reduce ambiguity.
The slides of his presentation can be found on the ETRL website.
Scientific lecture
The meeting concluded with an interesting scientific Lecture by Alessandro Marchese (VUB, Brussels, Belgium) on AI models in liver transplantation. He showed both advantages and threats of the use of AI models. His presentation is published on the ETRL website.