Genotyping for extended and rare blood types

Introduction 

Blood typing is a medical service commonly used to determine whether a patient who needs a transfusion can safely receive donated blood. It pairs donor blood with recipients, and the need to identify a match precisely and reliably is critical. Transfusion with the wrong blood type can cause a variety of adverse reactions. For instance, if someone receives incompatible blood, their immune system can form antibodies (alloantibodies and autoantibodies) to the foreign red blood cell (RBC) antigens in the donated sample. These antibodies can then increase the risk of a severe, even life-threatening, reaction (RBC alloimmunization) to future blood transfusions.  

Researchers estimate the risk of developing RBC alloimmunization after the transfusion of a single unit of blood to be <1%; however, the risk may increase significantly for those who receive frequent transfusions, such as patients undergoing chemotherapy and people with inherited blood disorders like sickle cell disease and thalassemia [1]. The incidence of alloimmunization in patients with sickle cell disease has been particularly well studied and is reported to range from 18% to 65% [2]. 

Reducing the risk of adverse reactions from transfusions is a multifaceted challenge. One of the foundational elements needed is a comprehensive solution that can improve and expand donor blood matching for extended and rare blood types. This could help reduce the risk of alloimmunization and could even help blood services increase rare blood donations.  

Blood donations around the globe [3] 

• About 118.5 million blood donations are collected globally each year. 

• From 2008 to 2018, blood donations from voluntary unpaid donors increased by 10.7 million. 

• Systems for reporting adverse transfusion events are present in 55% of the hospitals performing transfusions  

The challenges to improving and expanding donor blood matching for extended and rare blood types  

Several hurdles must be overcome to improve and expand donor blood matching for extended and rare blood types. Among the top challenges are the limitations of conventional blood typing, the lack of access to scalable, cost-effective extended blood typing, and ongoing blood shortages worldwide [4].  

Conventional blood typing lacks precision and reliability  

The first system for classifying blood group systems was established in the early 1900s. It categorizes blood into one of four main types (A, B, AB, and O) and determines whether the blood is RhD positive or RhD negative. Although this type of testing has long been considered the gold standard for blood typing, modern transfusion medicine recognizes many more blood types that are relevant to patients in need of frequent transfusions.  

Modern molecular biology techniques have transformed the way blood can be classified, and today’s newer methodologies offer much more precision and reliability than conventional testing. Notably, there are now 45 recognized blood group systems containing 360 RBC antigens [5]. These antigens are surface markers on RBC membranes. While their functions are not fully understood, knowing which antigens are present is important for avoiding adverse transfusion reactions, particularly for people at high risk of developing alloantibodies.  

Testing for extended blood types is resource-intensive  

Although advanced molecular methods for extended blood typing have been developed, in today’s testing paradigm, these methods remain resource-intensive. For instance, genetic sequencing can be used for advanced blood typing, but the high cost is prohibitive for widespread blood services testing. Running molecular blood tests is currently largely manual and also typically time-consuming and labor-intensive. To type a donor for all blood groups, tissue types, and platelet types requires different labs, different experts, and different machines. In addition, current tests for rare blood types may not always be accurate. As a result, extended blood typing is typically reserved for only a small number of cases, such as returning donors with known rare blood types.  

Blood shortages make finding donor matches even more difficult, especially for people with rare blood types  

In addition to the challenges related to testing, the difficulties of improving and expanding donor blood matching for extended and rare blood types are exacerbated by blood shortages, which remain a problem for most countries worldwide [6]. While these shortages jeopardize all patients in need of transfusions, the risks are intensified for patients with rare blood types—and even more so for those with rare blood types who require frequent transfusions. 

When a patient requires a rare blood transfusion, the hospital where they are being treated first looks for a match in its in-house blood bank. If it is not available, a call is put in to their blood supplier. In some cases, suppliers need to screen hundreds of donors to find a compatible unit of blood. If the supplier does not have that blood type available, they will turn to programs such as the American Rare Donor Program (ARDP) and the International Rare Blood Panel. The demand for blood donors is urgent: 

• The ARDP reports that it receives more than 1,000 requests for rare blood every year from hospitals and blood suppliers when they cannot fulfill donor needs with their own supplies [7]. 

• In the US, it is estimated that over 100,000 people have sickle cell disease. Individuals with sickle cell disease can require frequent blood transfusions throughout their lifetime needing as many as 100 units of blood each year—to treat complications of the disease [8]. 

• In 2022, demand for donations reached record levels in England, and the National Health Service put out an urgent call for donors to give blood to help people with sickle cell disease. At the time, the country was only able to meet half of the 250 donations needed each day for people with sickle cell disease [9]   

Rare and ultra-rare blood types  

 The presence or absence of antigens creates rare blood types. Blood is considered rare if it lacks antigens for which 99% of other people are positive. Blood is considered ultra-rare if it lacks an antigen for which 99.99% of other people are positive. Fewer than 50 people in the world have the rarest of all blood types, Rh-null, which is sometimes called “golden blood” [10,11]. 

Solutions for improving and expanding donor blood matching for extended and rare blood types  

Patients who need transfusions can benefit from advances in blood typing methodologies, especially if those methods are scalable, cost-effective, and easily accessible.  

Advances in medical science enable more precise blood typing  

Since the advent of modern molecular biology in the 1980s, researchers have been steadily evolving techniques to enable more advanced blood typing, especially for extended and rare blood types. For example, the genes for different blood group systems have been identified, along with the mutations and other causes responsible for the variation seen in different blood group alleles [12].  

Advanced blood typing enables precise red cell antigen profiles that can improve patient care. In one recent study, genotyping was shown to be more accurate than phenotyping, leading to its implementation as the primary method for extended RBC typing for patients with sickle cell disease [13].  

Health groups call for more precise blood testing for patients and donors  

Because of the advances in blood genotyping, the Centers for Disease Control and Prevention (CDC) now advises patients with sickle cell disease to ask for an extended red cell antigen profile, share the results with healthcare providers before blood transfusions, and request blood matching [14]. In addition, the British Journal of Hematology published guidelines in 2016 on blood transfusion in sickle cell disease, noting that “Patients with sickle cell disease must also have extended RBC antigen typing performed, which may assist with further blood research and selection of red cell units” [15]. The guidelines also recommend that all patients with sickle cell disease carry a transfusion card that includes any information on alloantibodies.  

In order to match patients to donor blood as precisely a  possible, the donor blood must also be tested using advanced methods. As early as 2002, research demonstrated the benefits of DNA-based genotyping to enable more accurate selection of blood donor units for managing transfusions in patients with sickle cell disease [16]. Researchers have even called for universal high-throughput red blood cell genotyping for patient and donor populations and the creation of a national database to enable more precise donor blood matching for people with sickle cell disease [17]. Similarly, studies have also shown the value of extended RBC typing to find suitable blood units for multi-transfused patients with thalassemia [18]  

Currently, blood services use racial backgrounds of donors to help guide blood matches, as populations including African Americans, Hispanics, and Eastern Europeans are known to have higher rates of certain rare blood types [19]. Others have initiated programs to test donations for rare blood groups. Stanford Blood Center, for example, now performs in-depth molecular testing on approximately 50 blood units per week to ensure that information on rare donor blood is available when a patient needs it [20]. Not only does the program enable more precise, safe blood donations for patients, but the blood center is also able to reach out to donors with rare blood types asking them to consider donating again to ensure that blood type is available for patients in need.  

The Axiom BloodGenomiX Array for comprehensive, cost-effective blood genotyping  

To expand more precise blood typing, blood service centers need a high-throughput, universal DNA-based blood typing solution to analyze more blood groups without the need for multiple tests. To address this need, Thermo Fisher Scientific developed the Applied Biosystems™ Axiom™ BloodGenomiX™ Array. The Axiom BloodGenomiX Array covers most blood group systems as well as other tissue (HLA) and platelet (HPA) types to help enable more precise blood and platelet typing. Used on the Applied Biosystems™ GeneTitan™ MC Fast Scan Instrument, the array uses an advanced probe design to target the markers and copy number variations within complex regions associated with blood types. The data from the array are then automatically analyzed through the specialized Applied Biosystems™ BloodGenomiX™ Reporter software, a proprietary single software tool, to provide identified blood types. 

As explained earlier, extended blood typing has traditionally been an expensive, time-consuming, and largely manual process. The Axiom BloodGenomiX Array and software change that by enabling molecular genotyping for extended and rare blood types. Instead of running multiple tests requiring specific reagents and expertise, labs with the Axiom BloodGenomiX total solution will be able to detect most extended and rare blood groups in a single assay. In addition, the high-throughput assay and analysis requires minimal hands-on time and can be run by existing lab staff with minimal training.  

References 

1. Alves VM, Martins PR, Soares S, et al. Alloimmunization screening after transfusion 

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2.  Sins JW, Biemond BJ, van den Bersselaar SM, et al. Early occurrence of red blood cell alloimmunization in patients with sickle cell disease. Am J Hematol. 2016;91(8):763-769. doi:10.1002/ajh.24397 

3. https://www.who.int/news-room/fact-sheets/detail/ blood-safety-and-availability 

4. Kuehn B. Widespread Blood Shortages Threaten Global Public Health. JAMA. 2019; 322(23):2276. doi:10.1001/jama.2019.20070 

5. https://www.isbtweb.org/isbt-working-parties/rcibgt.html 

6. Raykar NP, Makin J, Khajanchi M, et al. Assessing the global burden of hemorrhage: The global blood supply, deficits, and potential solutions. SAGE Open Med. 2021;9:20503121211054995. Published 2021 Nov 10. doi:10.1177/20503121211054995 

7.  https://www.aabb.org/news-resources/news/article/2022/03/21/ diversity-in-the-blood-donor-pool-protects-patients-in-need-of-rare-blood 

8.  https://www.redcross.org/about-us/news-and-events/press-release/2021/red-cross-launches-national-initiative-to-reach-more-blood-donors-to-helppatients-with-sickle-cell-disease.html 

9.  https://www.bbc.com/news/uk-63155204 

10. https://www.redcrossblood.org/donate-blood/blood-types.html 

11. https://my.clevelandclinic.org/health/treatments/21213-blood-types 

12. Gorakshakar A, Gogri H, Ghosh K. Evolution of technology for molecular genotyping in blood group systems. Indian J Med Res. 2017;146(3):305-315. doi:10.4103/ijmr. IJMR_914_16 

13. Casas J, Friedman DF, Jackson T, et al. Changing practice: red blood cell typing by molecular methods for patients with sickle cell disease. Transfusion. 2015;55: 1388-1393. doi:10.1111/trf.12987 

14. https://www.cdc.gov/ncbddd/sicklecell/betterhealthtoolkit/bloodtransfusions.html 

15. https://b-s-h.org.uk/guidelines?search=sickle+cell+disease 

16. Castilho L, Rios M, Bianco C, et al. DNA-based typing of blood groups for the management of multiply-transfused sickle cell disease patients. Transfusion. 2002;42(2):232-238. doi:10.1046/j.1537-2995.2002.00029.x 

17. Karafin MS, Howard J. Genotyping and the future of transfusion in sickle cell disease. Hematol Oncol Clin North Am. 2022;36(6):1271-1284. doi:10.1016/j.hoc.2022.07.012 

18. Belsito A, Costa D, Signoriello S, et al. Clinical outcome of transfusions with extended red blood cell matching in β-thalassemia patients: A single-center experience. Transfus Apher Sci. 2019;58(1):65-71. doi:10.1016/j.transci.2018.11.006 

19. https://www.redcrossblood.org/donate-blood/blood-types/diversity.html 

20. https://stanfordbloodcenter.org/pulse-sbc-begins-testing-donations-for-rare-blood-groups/