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titleWhy are there sometimes probabilities missing?

This can have several causes.

  • Overall match probabilities and locus-specific match probabilities are missing: this is most likely because the HLA typing of the donor/CBU is not consistent with any known haplotypes for the population that the donor is in
These donors don't have haplotype probabilities. This is usually the case when the phenotype could not be explained with the haplotypes given in the frequency set
  • (inexplicable donor). Without haplotypical context, the matching engine is not able to provide match probabilities. 
  • Only locus-specific match probabilities are missing: It does not make sense to display the probability of match for a specific locus in case of a mismatch
    • Because the known match probability is 100% and therefore there is no probability of a(n additional) mismatch and therefore displaying match probabilities in case of an additional mismatch does not make sense.
    • Because the probability of an additional mismatch is 0% for another reason, e.g. because the donor is low resolution typed at 3 loci and therefore in theory be a match, but it is very unlikely.  

See the following page for more information: Feature differences Hap-E Search vs Optimatch

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titleWhy is, for example, a donor with B*15:BPXE not shown as a potential match for a patient with B*15:03?

Since B*15:BPXE = B*15:03/61/74/103 a donor with this codes is a potential allele match for the patient. According to the official WMDA serology/DNA correspondence table, B*15:61 and B*15:74 have a serology of B15/B70 while B*15:03 is B72 and B*15:103 is B70. As a consequence a serology of B15 rules out B*15:03 and this donor is no longer potentially identical (on the allele level). Another explanation could be the limited length of donor lists.

Background: Unfortunately, for many donors serology was derived from DNA (by using the first field for the serological assignment) and vice versa (by appending “:XX” to the serological assignment) and often eventually both values are reported. In the case discussed, B*15:BPXE probably was translated back into B15 which is most likely wrong. This is a typical and (with certain registries) frequent case but there are many more unexpected DNA-serology correspondences that can give rise to exactly the same situation.

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