Dear Search Coordinators,
Planned implementation date (TBC): 19th to 21st of September 2026
As part of WMDA’s continuous commitment to supporting accurate and clinically relevant donor search and matching processes, updates associated with the HLA Nomenclature 2026 release are planned to be implemented in WMDA Search & Match services between 19th to21st of September 2026. These dates are tentative and subject to change pending the outcome of user testing.
IMPORTANT TO NOTE: The usual 1 year grace period on changed nomenclature does not apply to the changed serological assignments. There will be no grace period following the release planned in September.
These changes reflect the latest consensus and scientific understanding of HLA nomenclature and serological assignments. The update represents an important improvement in the interpretation of HLA data and ensures that matching services remain aligned with current international standards.
What is changing?
The HLA Nomenclature 2026 update introduces revisions to certain serological assignments associated with specific HLA alleles. As a result, some patient-donor combinations may receive a different serological interpretation than under previous nomenclature versions. While the underlying HLA typings remain unchanged, the revised serological assignments may affect how allele differences are classified from a matching perspective.
For example, allele combinations that were previously interpreted as an allele mismatch with antigen match may now be classified as an antigen mismatch because the corresponding alleles are assigned to different serological specificities under the revised nomenclature.
These changes are expected and are a direct consequence of the updated nomenclature definitions. They represent a refinement of matching interpretation rather than a change to the biological characteristics of the donor or patient.
The implementation has been coordinated across the matching services supporting WMDA Search & Match to ensure consistent application of the HLA Nomenclature 2026 updates from the effective date. While individual matching solutions may differ in their internal implementation, all participating providers will apply the revised nomenclature and associated serological assignments in accordance with the updated standards.
Impact on WMDA Search & Match
For users of WMDA Search & Match, the expected impact is primarily related to the classification of certain mismatches resulting from the revised serological assignments.
Specifically, users may observe:
- Changes in the distinction between allele mismatches and antigen mismatches for selected patient-donor combinations.
- Updated matching categorizations and matching results that reflect the revised serological interpretations.
- Differences in match grading and match assessment for some donor-patient pairs compared with results obtained prior to the implementation date.
At this time, no broader changes to matching logic are anticipated beyond those resulting directly from the revised serological assignments introduced with HLA Nomenclature 2026. Overall, the impact on WMDA Search & Match results is expected to be limited and confined to donor-patient pairs affected by the updated serological definitions.
Awareness for Search Coordinators and Search & Match Users
Search Coordinators and all users of Search & Match services should be aware that match assessments for certain donor-patient combinations may differ following the implementation.
When reviewing historical searches or comparing results generated before and after 21st of September 2026, users may encounter cases where previously reported allele-level mismatches are now classified as antigen mismatches.
These differences do not indicate a data quality issue. Rather, they reflect the adoption of the latest HLA nomenclature and serological assignment standards. WMDA recommends that search teams take these changes into account when interpreting search results generated after the implementation date.