The era in which standard serology tests divided populations into two basic blood groups, ABO and Rh, may soon be a thing of the past. Nearly a century after blood group analysis began, new technologies for genotyping of blood offer a far more accurate picture of blood groups, experts reported at the 12th Congress of the European Hematology Association.
Safety of blood transfusions, donor-recipient compatibility, and efficiency in managing blood banks may all receive a significant boost with genotyping, says Professor Neil Avent, from the Bristol Genomics Research Institute in the UK. Professor Avent has just led a three year study on the subject and at the European Hematology Association Congress in Vienna from June 7 to 10, presented the Bloodgen Project, looking at mass scale comprehensive genotyping of blood donors in the EU and beyond. Ideally, in future, says Professor Avent, as comprehensive genotyping becomes the norm, all of us will know to which of the nine main blood groups we belong.
Safety of transfusion increased
There are in reality not just the two types of blood group system (the ABO system and the Rh system) which standard tests establish, but 29 sub-types. Genotyping technologies recently developed and tested in the study led by Professor Avent focus on the nine most important and clinically significant groups- this includes the ABO group and the Rh group as well as seven more major groups. Improved blood matching has implications for everyone. For example, a woman of child bearing age receiving a blood transfusion with poor compatibility may develop antibodies leading to complications during pregnancy in the baby's immune responses. Similarly, a major transfusion, for instance after an accident, if donor-recipient compatibility is not optimal may mean a patient develops antibodies which can complicate any future transfusion.
While as much as possible is done with cross matching of donors and recipients in current serology testing to ensure complications are minimized, with the far greater accuracy offered by genotyping of blood, the safety of transfusions will obviously be increased, Professor Avent points out.
Genotyping offers advantages when speed is crucial
Genotyping will allow blood banks to store blood supplies for which highly accurate genetic profiles are already done. Should a patient whose blood group is not already established require a transfusion, their blood can then be genetically tested, the antibody profile established and a match made from stores already indexed. This offers significant savings in time and effort in the logistics of providing blood to recipients. Currently, cross match testing with standard serology techniques can be very complicated and time consuming in patients with a large numbers of antibodies. Thus in emergencies, when speed of medical intervention is crucial, genotyping offers major advantages. The fact is, says Professor Avent, DNA reactions are much easier to control than serology testing. Thus genotyping can revolutionize the way blood banks and hospitals operate.
From the broader perspective, use of DNA data can be expected to become standard in terms of the entire medical system, for instance in treating genetically determined diseases and establishing patient toxicity to drugs, so it would appear feasible to see blood supply, a fundamental part of medical procedures, brought into line with these developing technologies.
Improvement in safety
Another significant aspect of genotyping is screening for rare blood groups. There are between 500 and 600 rare Rh variants which are not tested for with standard serology techniques, as these tests are time consuming and can be very difficult. But with the comprehensive platform offered by genotyping of blood problematic supplies can be excluded from the blood donor pool. These rare blood groups range from 1 in 4,000 carriers in the general population to 1 in 30,000 as the three year clinical trial undertaken by Professor Avent’s team showed. But collectively they are quite common and thus significant. Without wishing to exaggerate the dangers of current blood supplies, it is time to acknowledge that they are potentially a clinical problem, and that genotyping offers an important improvement in safety, says Professor Avent. People with rare blood groups receiving transfusions can be assured of compatible supplies, while these people should be excluded from donating blood to banks.
European standard within 3-4 years
Blood genotyping is not yet commercially released as a technology. At first glance, costs appear significantly higher than for serology tests, but such comparisons are misleading if the far more comprehensive level of information they yield is taken into account. Professor Avent says he hopes to see genotyping as a standard technology in Europe within three to four years. Holland, the UK, France and Germany are currently looking at the issue. At this point, blood banks need to do trials and introduce it themselves. Beyond Europe, and within it in the days of significant immigration, mass scale genotyping clearly also offers an answer to the highly variable blood profiles of different ethnic groups.
Source: European Hematology Association