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If this is the case then most likely the PATIENT has HLA typing that cannot be explained by a combination of two haplotypes in the haplotype frequency (HF) set that was applied to the patient HLA by the matching engine. When no "pool" is provided this is the global HF set and if there is a pool provided then the country code provided is used to pick the corresponding HF set.
How to "fix" the issue
In order to make the patient "explicable", there are two options:
Option 1:
Change the "Pool Country Code" of the patient to "No Value". That way the global HF set is applied and this is most likely to contain a combination of haplotypes that explains the patient typing. If that does not help, in some cases it may be useful to set "Pool Country Code" to the country that corresponds to the genetic background of the patient.
Option 2:
Re-type the patient at high resolution so that all ambiguity in the HLA typing is removed. When all ambiguity is removed from the patient side the matching engine is able to calculate matching probabilities again.
If this is done you will see the following types records in the results:
- Low and intermediate resolution donors with an overall match probability of 0%. The match probability is 0% because even though there is a theoretical possibility that the donor has the same genotype as the patient, there is no combination of two haplotypes in the HF set of the donor that would result in the genotyping needed to be a match to the patient. In ATLAS these donors would not be returned.
Please keep in mind that some of these donors could be a match with the patient, especially when they have the same genetic background as the patient. - You may see a high resolution typed donor that is a 100% match. This is unlikely considering the fact that the patient has a very unique genotype, but it is possible.