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There is not a single system for HLA matching. For transplants, there usually needs to be at least a 4 of 6 match. The DR, DQ, A, B, C, and DP regions need to be tested. DR, DQ are Class II which are mostly what I deal with so that is where most of my knowledge lies. For DR, high-resolution testing is needed, meaning that when all the analysis is complete, allele-level results will be obtained. First the general testing is done, which will identify the major probes that the specimen has (DRB1*01, DRB1*07, etc). Depending on the major probes involved, further subtype processing will need to happen, and possibly even secondary testing. Once those results have been obtained, usually by sequence-specific oligonucleotide probing, the sample might be at allele-level by this stage. Otherwise, no further processing on the SSOP side can occur and the specimen will need to be reflexed to either SBT (sequence-based typing) or SSP (sequence specific priming). Between these results and the SSOP results, allele-level results have usually been obtained and a match/no match can be determined.