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Biannual Rare Allele ListsThe NMDP maintains lists of rare alleles as a service to the American Society for Histocompatibility & Immunogenetics (ASHI). These lists are derived from HLA allele level typings of patients, adult volunteers, and cord blood units in the NMDP Registry. Rare alleles for the HLA-A, B, C and DRB1 loci are listed in separate files for the corresponding release version of the IMGT HLA Database. Beginning with IMGT release 2.16.0, a separate listing of rare allele differences between the current and previous list is included. The most recent version of the IMGT HLA Database can be found at: http://www.ebi.ac.uk/imgt/hla/ This list does not represent allele frequencies. Rather, this list shows the number of times a particular HLA allele appeared in the NMDP registry. Depending on the time at which the reporting laboratories incorporated a new allele into their typing interpretation, donors may or may not have been tested for the allele. For example, allele A*0251 was reported on May 31, 2001. Samples tested prior to 2002 were not tested for allele A*0251. The number of occurrences of allele A*0251 reflects only those subjects tested after 2002 assuming typing laboratories utilized typing kits which incorporated allele A*0251 after it was described. Also, these allele data do not reflect a random sample from the population due to variables such as typing and reporting methods and recruitment and search strategies. Therefore, the number of times the allele occurs can only be considered an observation and does not represent its frequency in the population. Rare Allele List Files
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