HLA typing for post-transfused patient: comparison between blood and buccal swab sample

ABSTRACT

Background: The polymorphic Human Leukocyte Antigens (HLA) play an important role in determining the best matched donor in a haematopoietic stem cell transplant (HSCT). Hence, accurate HLA typing results are crucial to determine the successfulness of a transplant. Most of the patients of hematologic diseases will receive blood transfusion regularly. There is a potential discrepancy result or ambiguous results when a patient already received non-leukoreduced blood component prior to blood sampling for HLA typing. Aims: To determine differences between the HLA typing result from the DNA extracted from blood sample and buccal swab sample. Methods: Blood sample and buccal swab sample were collected from a total of 66 patients with different hematologic diseases and plan to go for haematopoietic stem cell transplant. These patients received at least one pack of red blood cell or platelet between 1 and 14 days prior to blood sample taken. DNA was extracted from all 66 blood samples and 66 buccal swab samples. All samples were typed for six loci (HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQB1 and HLA-DPB1) with Next Generation Sequencing (NGS). NGS was performed in all those samples using the NGSgo-MX6-1 kit. After the library preparation by using NGSgo-LibrX ligation reagents and the NGSgoIndX adapter, it was sequenced in iSeq 100. The results were then analysed with NGSengine software. The results for blood sample and buccal swab sample were then compared. Results: Out of 66 patients, 25 patients received either red blood cell or platelet component prior to blood sample taken for HLA typing. One patient received red blood cell and plasma and the others received red blood cell and platelets before the sample was taken. There are no differences between the HLA typing result from the DNA extracted from blood sample or buccal swab sample for all the 66 patients. The sequencing noise level for both DNA extracted from blood and buccal swab was well separated from the alleles as we can see from the base variation plot. Summary/Conclusions: This preliminary study only focus on the adult patients with hematologic diseases (ALL, AML, CML, MDS, multiple myeloma, DLBCL, hemophagocytic lymphohistiocytosis, NKT Cell lymphoma and severe aplastic anaemia) for the past 1 year. From the findings of this study, blood samples from the patient who underwent blood transfusion can be used for HLA typing instead of using buccal swab samples. This will lower the risk of Covid-19 infection among the healthcare worker who performs the buccal swab sampling from the patient with unknown status of Covid-19 infectivity. However, an extensive study with the appropriate number of samples needed to confirm this finding in the near future.