Daniel Gay
A new system allows for accurate blood group typing at the DNA level, on a large scale and at a relatively low cost, according to a paper published in The Journal of Molecular Diagnostics.
Researchers designed this automated genotyping system using 96-well DNA microarrays for blood donation screening and a panel of 8 single-nucleotide polymorphisms (SNPs) to identify 16 alleles in 4 blood group systems—KEL, KIDD, DUFFY, and MNS.
The team said they developed this system because conventional hemagglutination falls short in 2 ways: it’s time consuming and involves a limited range of antigen testing.
“In the French Blood Service, the Etablissement Français du Sang (EFS), blood donation qualification laboratories test all blood donations for A, B, O, Rhesus, and KEL blood groups, but only 5% to 10% of donations are tested for other clinically significant antigens [such as FY1, FY2, JK1, JK2, MNS3, and MNS4],” said study investigator Jean-Charles Brès, PhD, of EFS Pyrénées Méditerranée in Montpellier, France.
So he and his colleagues developed their system—a robotic platform using a 96-well DNA microarray for multiplex blood group genotyping.
They designed an SNP module to allow for simultaneous determination of KEL (KEL*01/KEL*02, KEL*03/KEL*04), KIDD (JK*01/JK*02), DUFFY (FY*01/FY*02, FY*02M.01 or FY*X, and FY*02M.02 or FY*Fy), and MNS (GYPA*01/GYPA*02 or MNS*01/MNS*02, GYPB*03/GYPB*04 or MNS*03/MNS*04) blood group antigens.
The researchers tested the system in a pilot study, using 1132 EDTA-anticoagulated blood samples collected by the EFS. Random donors, mostly Caucasian, were extensively phenotyped using standard serologic hemagglutination techniques.
The team used 172 samples to determine scoring criteria for predicting phenotype and the remaining 960 samples for validation of the 96-well DNA microarray system.
A total of 938 samples were considered valid and assigned genotypes based on the scoring criteria determined for the 8 SNPs. Twenty-two samples were invalid because they were considered “uninterpretable” for all SNPs.
The researchers compared the phenotypes predicted from genotypes with those obtained by serologic typing. And they found the concordance rates between the DNA-based and standard hemagglutination assays were high.
The overall concordance rate was 99.92%. There was 100% concordance for KEL*03/KEL*04; GYPA*01/GYPA*02; and FY*01/FY*02/FY*02M.01/FY*02M.02. And the concordance rate was 99.89% for KEL*01/KEL*02; JK*01/JK*02; and GYPB*03/GYPB*04.
So the researchers said that, overall, this system appears effective. They also noted that the system allows for simultaneous multiplex assay of up to 96 samples in a single reaction run. But other DNA microarray formats with a lower number of wells can be processed as well.
For small batch production, the cost of genotyping, including genomic DNA extraction, labor, and equipment, was less than $2.60 per SNP for a multiplex set of 8 SNPs, which is 4 times lower than the per-antigen cost using serologic methods.
“In addition to providing more fully antigen-matched [red blood cells] and allowing better identification of rare donor blood types, this technology will reduce adverse reactions and decrease the relative cost of analysis,” Dr Brès said.
“High-throughput DNA typing could facilitate support for patients undergoing long-term transfusion who are at high risk of alloantibody production, such as patients with sickle cell disease, thalassemia, or autoimmune hemolytic anemia.”
