The following links list how search determinants are assigned to each HLA allele by the different registries; The Anthony Nolan, the NMDP, BMDW, Canadian Unrelated Bone Marrow Donor Registry, France Greffe de Moelle, BBMR and also the ZKRD approach to search determinants.

National Marrow Donor Program (NMDP)

The National Marrow Donor Program (NMDP) has made enhancements to its matching algorithm. The enhancements are called HapLogic™. The HapLogic™ algorithm no longer uses search determinants for the initial matching step as this is now done by directly comparing patient DNA type to donor DNA type. The algorithm is able to account for all serologic typing possibilities with the use of a special table called the "Serology to DNA Allele Table". This ensures that no potentially matched donor is likely to be missed. Search determinants are still used to assign match grades when patient and donor types do not match. The search determinant of the patient is compared to the search determinant of the donor to determine if the mismatch is at the allele level or if the mismatch is at the antigen level. When search determinants of patient and donor match, the mismatch is determined to be an allele mismatch. When search determinants of patient and donor do not match, the mismatch is determined to be at the antigen level. Search determinants for both Class I and Class II alleles are now the first two digits of the allele family name, with the exception of the B15 and B40 families. NMDP maintains a special Ad Hoc Search Determinant Committee which meets annually to review all search determinant assignments as well as the "Serology to DNA Allele Table". The committee provides expert advice and guidance as to the best assignment for each allele. The data used to review search determinant assignments includes serologic information from the WMDA HLA DNA-Dictionary (including information from the UCLA Cell Exchange, NMDP registry, International Histocompatibility Workshop) and a neural network. The NMDP also maintains a set of search comments which provide additional search advice relating to particular alleles with unusual or multiple serologic specificities. These comments are triggered by the appearance of that allele on a search and appear in a special section of the computer software used by transplant centres.


Hurley CK et. al.
Hematopoietic Stem Cell Donor Registry Strategies for Assigning Search Determinants and Matching Relationships
Bone Marrow Transplantation (2004) 33(4):443-450


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