 Abstract | | |
BACKGROUND: Although ABO and RhD are the clinically significant blood group antigens that are routinely tested for, other blood group antigens may become important in multiply transfused patients due to risk of alloimmunization. Knowledge of antigen prevalence in a population is important in the context of alloimmunization and antigen matching. This study aims to do the same in a population of voluntary blood donors of a center in South India.
AIMS AND OBJECTIVES: To study the ABO, Rh (D, C, c, E, and e), and Kell (K) antigen and Rh phenotype prevalence in whole blood donors donating at the blood bank of a tertiary care hospital in South India.
MATERIALS AND METHODS: One thousand and two hundred eligible whole blood donors were chosen by random sampling between November 2017 and April 2019. After administration of informed consent and routine testing for ABO grouping, RhD typing, and indirect antiglobulin test, Rh and Kell typing was done on appropriate gelcards and the data were analyzed to arrive at phenotypes.
RESULTS: 97.6% of the donors were male and 2.4% were female. They were divided into 7 different categories based on the regions of origin: Kerala, Andhra Pradesh, Tamil Nadu, Karnataka, West Bengal, North India, and others with the largest number of donors hailing from Karnataka (38.5%). The ABO distribution, in descending order, was as follows: O (38%), B (34.5%), A (20.6%), and AB (6.8%). The prevalence of the Rh antigens was as follows: D: 93.4%, C: 87.9%, c: 55.6%, E: 19.3%, and e: 98.8%. K was present in 1.4% of the population. Since genotyping has not been done, the most common “presumed” Rh phenotype among RhD-positive donors was R1R1 (46.4% of total donors and 49.5% of RhD-positive donors). The most common phenotype among RhD-negative donors was rr (5.9% of total donors and 92.2% of RhD-negative donors). The order of prevalence of the ABO, Rh, and K antigens and the Rh phenotypes remained the same irrespective of gender, ABO group, and region of origin.
CONCLUSION: This population-based study analyzes a donor population as a whole and separately as per regions of origin and shows that antigen prevalence and thereby risk of alloimmunization does not vary markedly among the different population subsections. Hence, even where extended phenotyping and antigen matching cannot be done, risk of alloimmunization may be low. Limiting antigen matching to specific patient subsets like in multiply transfused patients with uncommon phenotypes may, therefore, be an efficient and cost-effective approach.
Keywords: Alloimmunization, antigen matching, phenotype
How to cite this URL:
Soumee B, Devi AM, Sitalakshmi S. Prevalence of ABO, Rh (D, C, c, E, and e), and Kell (K) antigens in blood donors: A single-center study from South India. Asian J Transfus Sci [Epub ahead of print] [cited 2023 Mar 24]. Available from: https://www.ajts.org/preprintarticle.asp?id=356864 |
| Introduction | |  |
To date, there are 33 blood group systems and over 300 red blood cell (RBC) antigens recognized by the International Society of Blood Transfusion.[1] In India, only ABO and Rh D status of blood donor and recipients are taken into account for compatibility testing.[2]
However, knowing the phenotype of clinically significant blood group antigens on the donor RBCs is important when alloimmunization is particularly undesirable, such as in pregnant women, and patients who are expected to be multiply transfused. For instance, the Rh and Kell antigens are highly immunogenic, and most of the Rh and Kell antibodies should be considered as potential causes of hemolytic reaction and hemolytic disease of fetus and newborn.[3],[4] In multiply transfused patients, risk of alloimmunization can be reduced by transfusion of phenotypically matched red blood cells for selective RBC antigens.[5]
However, variability in blood group phenotypes in different populations is responsible for the difference in the frequencies of alloimmunization.[6] Hence, knowledge of phenotypes in a particular population may be helpful in formulating population-specific transfusion guidelines, such as in the context of extended phenotype matched dedicated donors to thalassemia patients.
Studies on the Rh and Kell antigen prevalence in South India are few. This study aims to be a worthwhile addition to that collection. In addition, the novelty of this study is that it analyzes and compares the Rh phenotype prevalence patterns among donors of different regions of origin, which has important implications in understanding the risk of alloimmunization, and thereby the transfusion decisions in multiply transfused patients.
Aim and objectives
To study the ABO, Rh, and Kell antigen and phenotype prevalence in blood donors donating at the blood bank of a tertiary care hospital in South India, between November 2017 and April 2019.
| Materials and Methods | | |
This is an observational, descriptive study done prospectively over 18 months. After a thorough literature search of studies providing the prevalence percentage of the antigens of interest in this study, the study by Makroo et al.[7] was found to give the prevalence for antigen K as the lowest (3.5%) in a sample size of 3073. This was the largest sample size in all the Indian population-based studies on antigen phenotype prevalence that had been referred to and was used to estimate the sample size. To estimate the prevalence of 3.5% with 95% confidence interval and 1% relative precision, the required sample size was calculated as 1200.
Eligible blood donors were selected for the study by random sampling. There was a standard consent form drawn up for the purpose of this study and it was distributed to donors who consented to participating in the study when they came to donate at the inhouse blood collection center. The principal investigator counseled and administered this consent to these donors. Mother tongue was used as a marker to designate the geographical region of the donors and a brief family history was taken to include only people with a single state of origin.
Routine immunohematological tests performed on collected samples were ABO grouping, RhD typing, and indirect antiglobulin test. In addition, an extended phenotyping was done for C, c, E, e, and K antigens using column agglutination technology (ID-Card, DiaClon Rh-Subgroups+K, Biorad, Cressier, Switzerland) for donors participating in the study.
The results were documented along with the donors' demographic details, including region of origin, in an electronic spreadsheet and analyzed on Microsoft Excel 2010.
| Results | | |
Of the 1200 donors, 1172 (97.6%) were male and 28 (2.4%) were female.
The donors were classified according to the region of origin based on mother tongue. The most common ones were Karnataka (38.5%), Andhra Pradesh (22.2%), Tamil Nadu (15.4%), North India (8.5%), West Bengal (5.6%), and Kerala (4.6%). The remaining were classified under one category titled “Others” (4.8%).
The ABO group distributions were as follows: A - 248 (20.6%), B - 414 (34.5%), O - 456 (38%), and AB - 82 (6.8%).
1123 (93.4%) were RhD positive, whereas 77 (6.4%) were RhD negative. The order of prevalence of the ABO groups was the same among both RhD positive and negative donors.
The data were analyzed gender wise and the order of prevalence of the ABO groups was found to be the same as shown in [Table 1]. | Table 1: Summary of gender wise ABO and RhD type distribution in study donor population
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The overall prevalence of the Rh and Kell antigens (C, c, E, e, and K) in the study population was as follows: C: 1055 (87.9%), c: 668 (55.6%), E: 232 (19.3%), e: 1186 (98.8%), and K: 17 (1.4%). The phenotypes depicted here are “presumed” and arrived at after consulting similar studies.[8] The phenotype-wise distribution of the donor population is illustrated in [Table 2]. This order of prevalence was the same across both genders and all the 4 ABO groups. The Rh phenotypes were then analyzed and compared in the 7 categories based on the regions of origin, as mentioned above. This comparison is tabulated in [Table 3].
| Discussion | | |
Knowledge of the distribution of blood group antigens in a population is the first step toward further evaluating the necessity of antigen matching in β-thalassemia and other conditions mandating multiple transfusions.
Of the 1200 donors, 1172 (97.6%) were male and 28 (2.4%) were female. This mirrors the statistics published by the WHO of % of Indian blood donors: males, 94% and females, 6%.[9]
The distribution of ABO groups differs across populations due to various factors. In this study, the prevalence, in descending order was, O, B, A, and AB. A comparison with other Indian studies[10],[11],[12],[13] showed that this order varied across regions. It was evident that studies with a demographic similar to this study, such as the ones done by Sundar et al.[13] and Soonam et al.,[11] done on primarily Bangalore-based and Kerala-based populations, respectively, showed the same order of prevalence. Among Indians, the prevalence of the D-antigen has been reported to be between 93% and 94.5% by different studies.[14],[15],[16],[17],[18],[19],[20] As per the current study, the prevalence of D antigen was 93.4%.
The ABO group prevalence was studied separately among both genders. The prevalence of women donors among the ABO groups was as follows: A (1.2%), B (1.6%), O (3.2%), and AB (3.6%). This correlates well with the overall percentage of women donors in this study (2.3%) and with other similar Indian studies by Chandra et al.[14] The order of prevalence was the same in males, females, and the overall population, O>B>A>AB. In the present study, of the 28 women donors, only 3 donors were RhD negative (two were O negative), while one was AB negative. The prevalence of D antigen among the women donors was, therefore, 89.2% as compared to 93.6% among the males and 93.5% in the entire sample population.
A comparison of the prevalence percentages of the Rh antigens in the current study with that of other similar studies is shown in [Table 4] and it is evident that findings of these studies concur among themselves and with the results of the present study. The sample size of the present study and demographic is the closest to that by Gundrajukuppam et al.,[6] which was done on a predominantly South Indian population and had a sample size of 1000. However, the findings of this study concur better with the studies by Makroo et al.[21] with the largest sample size, i.e., 51,857 donors. | Table 4: Comparison Of prevalence of Rh antigens in Indian Studies with the present study
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The present study referred to a list of “presumed” phenotypes described by an Indian study by Kahar et al.[8] based on the antigens present, without using genotyping. The most common phenotype as per this study was R1R1 (46.4%). R2Rz was the least common (0%). Among the 77 RhD-negative donors, the most common phenotype was rr (92.2%). The least common was r'r'' (0%). This prevalence has been found to support that shown by other Indian studies.[6],[8],[21],[22],[23] R1R1 was the most common Rh phenotype overall in all these studies, while among the RhD negatives, it was rr.
The prevalence of the Rh phenotypes was analyzed gender wise, like that of the ABO and RhD antigens. The most prevalent phenotypes, in descending order, were R1R1, R1r, and R1R2 among both genders. Among RhD-negative individuals, the most prevalent phenotype was rr in both genders. This is similar to the observation of Gundrajukuppam et al.[6]
The comparison of the prevalence of the K antigen has been described to be 9% for Caucasians and 2% in African-Americans.[24] In Indian population, this has ranged between 0.79% and 3.5% in various studies.[2],[7],[25],[26],[27] In this study, it was 1.4%. The sample size of the present study, at 1200, is in the range the studies by Lamba et al. (1000)[2] and Basu et al. (1528),[25] and at 1.4%, so is the prevalence percentage for K (2.8% and 0.79%, respectively).
The donor population was predominantly South Indian, but there were donors from other regions of India as well. Expectedly, the South Indian states made up for the greatest percentage of these donors (80.9%) with Karnataka being the highest (38.5%). This approach of analyzing the overall and segregated antigen and Rh phenotype prevalence is unique to this study. The findings, however, show that despite the variation in regions of origin of the donors, distribution of ABO antigens and order of prevalence of Rh phenotypes were similar across all subgroups of the population. The order and range of percentages of prevalence in descending order, among the RhD-positive donors, in all subcategories was R1R1 (32.1%-55.8%), R1r (23.9%-40%), and R1R2 (6.8%–16%). Among RhD-negative donors, the prevalence of the most common phenotype, rr, ranged from 87% to 100%. Difference in the percentages among the 7 subcategories can be the effect of their greatly differing percentage in the sample population.
The order of prevalence of the ABO antigens in this study population can be extrapolated to the general population, including patients. The Rh phenotype prevalence was also studied among all the four ABO groups to estimate the Rh phenotype distribution of the people of the different ABO groups. These data can be used for both patients and donors and can have important implications in any future attempts at antigen matching. The order of prevalence of the most common Rh phenotypes in descending order among RhD-positive donors is R1R1 (43.9%–48.2%), R1r (26.5%–31.4%), and R1R2 (12%–14.6%) among all ABO groups. In the RhD-negative donors, the most common phenotype was rr among all ABO groups. This is similar to the observation of Gundrajukuppam et al.[6] who reported the same order of prevalence of the Rh phenotypes across the ABO groups. Despite the large variation in the number of donors in each ABO group, the phenotype prevalence percentages concur well among all categories, which, in turn, implies that the risk of alloimmunization can be expected to be low even if extended antigen matching cannot be done routinely before transfusions.
Newer studies dealing with phenotypic distribution of ABO, Rh, and Kell antigens in North Indian donors (Pahuja et al.[28]) and Northwestern Indian donors (Prinja et al.[29]) and more localized studies dealing with antigen prevalence among donors in Uttarakhand (Kumar et al.[18]), Puducherry, and Tamil Nadu (Gopal et al.[30] and Srikumar et al.[31]) have also been compared with that of the present study in [Table 5] to comparable results. | Table 5: Comparison of Antigen and phenotypic prevalence percentages in newer Indian studies
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Infrequent phenotypes, such as C-negative and e-negative patients, may be at a higher risk of alloimmunization if phenotype-unmatched blood is transfused to them. If alloimmunization develops, it will also be difficult to find compatible blood due to high prevalence of the antigens. The cost-effectiveness of extended antigen phenotyping has been debated extensively. In resource-limited settings of developing countries, it may not be feasible to routinely do extended phenotyping for all blood donors. However, in patients with conditions where multiple transfusions are expected, phenotyping them before the start of transfusion therapy may be a more efficient approach. Antigen-matched blood can then be considered only in those with phenotypes found infrequently in the population.
One limitation of this study is the low number of female donors. Further, development of alloimmunization, if any, will have to be studied in recipients of blood from donors with rare phenotypes. Studies also need to be done comparing rates of alloimmunization in recipients of antigen-matched and unmatched blood to assess cost-effectiveness of antigen matching or routine extended phenotyping of all donors and/or patients. Furthermore, phenotyping in blood donors can be extended to other blood group antigen systems.
| Conclusion | | |
The order of prevalence of the ABO antigens were O>B>A>AB. The order of prevalence of Rh antigens were e (98.8%)>D (93.4%)>C(87.9%)>c (55.6%)> E (19.3%) . The most common Rh phenotype among RhD positives was R1R1 and rr among RhD negatives.
This order of prevalence remained the same irrespective of gender, ABO group, and region of origin. There was uniformity between the findings of this study and other relevant ones, especially in terms of Rh and Kell phenotypic prevalence. Antigen prevalence and thereby risk of alloimmunization does not vary markedly among the different population subsections. Hence, risk of alloimmunization may be low, even where extended phenotyping and antigen matching cannot be done. Limiting antigen matching in specific patient subsets like multiply transfused patients with uncommon phenotypes may, therefore, be a feasible and cost-effective approach.
Ethical approval
All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional ethics committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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Correspondence Address:
A. M. Shanthala Devi,
Department of Transfusion Medicine and Immunohematology, St. John's Medical College, Sarjapur Road, Bengaluru - 560 034, Karnataka
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/ajts.ajts_159_21
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5] |
