Page 180 - GSTL_21st May 2020_Vol 36_Part 3

426 GST LAW TIMES [ Vol. 36
“Description of methods and resolution :
• General Testing
The samples (except SSP and SBT of the clinical laboratory)
will be processed within our workflow using next generation
sequencing. HLA testing will be based on the regions covering
the peptide-binding domains and in addition exon 3 for HLA
class II genes. Therefore, regions sequenced are Exons 2 and 3
for HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1. In rare cases
HLA class II results will be based on Exon-2 only (=peptide
binding site). For class I in some cases additional sequences
are added to achieve phasing of exons 2 and 3. Currently,
more than 99% of HLA class I results (HLA-A, -B, -C) and
HLA class II results (HLA-DRB1, -DQB1, - DPB1) can be de-
livered as high resolution results in accordance with NMDP
criteria (null alleles determined by differences outside exons 2
and 3 cannot be excluded). The typing results will be deliv-
ered electronically in accordance with the current HLA no-
menclature as G codes, multi-allele codes or (shortened) allele
names, depending on the resolution obtained.
• Blood Group testing (ABO, Rh)
Blood Group testing is done by molecular biological methods
only. No serological testings are carried out. Selected exons
are sequenced by NGS. Testings achieved with this method
have a high rate of concordance with serological testings. In
rare cases serological and molecular biological testings differ
due to changes outside of the sequenced regions. Submitted
testings may only be used for donor pre-selection. The Con-
tractor does not submit clinically applicable blood group test-
ings. Testing results for blood groups can be obtained for ap-
proximately 90% samples.
• CCR5 testing
CCR5 is a cell surface chemokine receptor of leukocytes, eg. T-
cells or macrophages. A 32 bp deletion in the corresponding
gene leads to a truncated non-functional protein. To detect this
32 bp deletion, a 453 bp amplicon is generated and subse-
quently sequenced. Testings are reported as either WT
(Wildtype) or Del32 for each copy designating a copy without
or with deletion, respectively. Typing results for CCR5 can be
obtained for approximately 96% of samples.
• KIR (Killer cell Immunoglobulin like Receptor) testing
We sequence exons 3, 4, 5, 7, 8 and 9 of the KIR genes to ena-
ble genotyping of the KIR genes at allelic resolution. Alleles
differentiated only by sequence variation outside the se-
quenced exons cannot be distinguished. In addition some am-
biguities arise due to the lack of phasing information between
exons. Those remaining ambiguities will be reported as GL
strings. In a small fraction of the genotyped KIR genes, the da-
ta quality is insufficient for reliable allele level genotyping. In
those cases, only the presence or absence of a respective KIR
gene is reported. In addition, for some samples no KIR geno-
typing result may be obtained. Overall, genotyping results for
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