| Popis: |
We and few other centers have reported the false homozygosity of one or two HLA antigens in several leukemia patients. However, only one case of leukemia with false homozygous typing of one haplotype has been reported. In all these reports, HLA typing were performed by luminex based sequence specific oligonucleotide (SSO), sequence based typing (SBT) or sequence specific primers (SSP) methods and only SSP could identify heterozygosity. We report three cases of leukemia patients, two with AML and one with ALL diagnosis, with chromosomal abnormalities who failed the HLA genotyping of one chromosome. As a results, false homozygous results were obtained. All testing were performed when patients were initially diagnosed. All three patients were typed by Next Generation Sequencing (NGS), SSO or one by Sequence Based Typing (SBT). Repeat HLA genotyping by both NGS and SSO using buccal swab or blood after induction therapy and patient’s remission revealed heterozygosity. The above cases indicates for the first time, that not only SSO or SBT, but also the revolutionized NGS HLA genotyping may reveal false homozygosity in leukemia patients who have many tumor cells in their blood with chromosomal abnormality. The fact that SSP can detect the second haplotype is more likely due to the use of much higher DNA in testing which results in higher amount of normal cells DNA from and therefore, amplified DNA may be visualized. We conclude that in order to avoid false HLA homozygosity, everyone dealing with patients with hematologic malignancies, must be aware of this problem and take proper precautions to either repeat testing with buccal swab when homozygous HLA typing has been detected or blood when patients is in remission. Laboratories utilizing only NGS must also be aware of this problem and take precautions in reporting homozygous results. Confirmation of HLA testing must be performed prior to selection of related donors or searching for an unrelated donors. |
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