Partial phenotyping in voluntary blood donors of Gujarat State.

INTRODUCTION: Partial phenotyping of voluntary blood donors has vital role in transfusion practice, population genetic study and in resolving legal issues. The Rh blood group is one of the most complex and highly immunogenic blood group known in humans. The Kell system, discovered in 1946, is the third most potent system at triggering hemolytic transfusion reactions and consists of 25 highly immunogenic antigens. Knowledge of Rh & Kell phenotypes in given population is relevant for better planning and management of blood bank; the main goal is to find compatible blood for patients needing multiple blood transfusions. The aim of this study was to evaluate the frequency of Rh & Kell phenotype of voluntary donors in Gujarat state.
MATERIALS AND METHODS: The present study was conducted by taking 5670 samples from random voluntary blood donors coming in blood donation camp. Written consent was taken for donor phenotyping. The antigen typing of donors was performed by Qwalys-3(manufacturer: Diagast) by using electromagnetic technology on Duolys plates.
RESULTS: Out of 5670 donors, the most common Rh antigen observed in the study population was e (99.07%) followed by D (95.40%), C (88.77%), c (55.89%) and E (17.88%). The frequency of the Kell antigen (K) was 1.78 %. DISCUSSION: The antigen frequencies among blood donors from Gujarat were compared with those published for other Indian populations. The frequency of D antigen in our study (95.4%) and north Indian donors (93.6) was significantly higher than in the Caucasians (85%) and lower than in the Chinese (99%). The frequencies of C, c and E antigens were dissimilar to other ethnic groups while the 'e' antigen was present in high frequency in our study as also in the other ethnic groups. Kell antigen (K) was found in only 101 (1.78 %) donors out of 5670. Frequency of Kell antigen in Caucasian and Black populations is 9% & 2% respectively. The most common Kell phenotype was K-k+, not just in Indians (96.5%) but also in Caucasians (91%), Blacks (98%) and Chinese (100%).
CONCLUSION: Phenotype and probable genotype showed wide range of variations in different races and religion. Reliable population based frequency data of Rh & Kell antigens has vital role in population genetic study, in resolving medico legal issues and in transfusion practice.

Introduction and Background

The Rh blood group is one of the most complex blood groups known in humans. This system was discovered 75 years ago when it was named (in error) after the rhesus monkey. It has become second in importance in the field of transfusion medicine.[1] It has remained of primary importance in obstetrics, being the main cause of hemolytic disease of the newborn (HDN).[2]

The complexity of the Rh blood group antigens begins with the highly polymorphic genes that encode them.[3] There are two genes, RHD and RHCE that are closely linked.[4] Numerous genetic rearrangements between them have produced hybrid Rh genes that encode a myriad of distinct Rh antigens.[5] Until date, 50 Rh antigens are known.[6]

The significance of the Rh blood group is related to the fact that the Rh antigens are highly immunogenic. In the case of the D antigen, individuals who do not produce the D antigen will produce anti-D if they encounter the D antigen on transfused red blood cells (RBCs) (causing a hemolytic transfusion reaction) or on fetal RBCs (causing HDN). For this reason, the Rh status is routinely determined in blood donors, transfusion recipients, and in pregnant females.[7]

Three methods of Rh nomenclature were described. Fisher-Race proposed that the Rh antigens were controlled by three closely linked genes giving rise to eight gene complex or haplotypes: CDe, cDe, cDE, CDE, cde, Cde, cdE, and CdE.[8] At the same time, Wiener proposed that there was only one Rh gene, controlling a number of blood factors, equivalent to C, c, D, E, and e.[910] Rosenfield[11] proposed a system of nomenclature based on serologic observation. Symbols were not intended to convey genetic information, merely to facilitate communication of phenotypic data. Each antigen is given a number, generally in the order of its discovery or its assignment to the Rh system. The antigen Rh1 is D in Fisher-Race terminology and it corresponds with the blood factor Rh0 according to Wiener.[10]

The Kell system, discovered in 1946, is the third most potent system at triggering hemolytic transfusion reactions and consists of 25 highly immunogenic antigens, all of which are peptides within the Kell protein encoded by the KEL gene.[12] Little data are available regarding the frequencies of the blood group antigens other than ABO and RhD in the Indian population.

Knowledge of Rh and Kell phenotypes in given population is relevant for better planning and management of blood transfusion services. The primary goal of any blood transfusion is to provide the patient with donor RBCs that optimally survive after transfusion and serve their function and to ensure that the patient actually benefits from the transfusion. To achieve this goal, donor red cells that are compatible with those of the patient's blood are selected for transfusion.[13]

The criteria for selection of donor cells focuses on the absence of antigens on donor cells for the antibodies that are detected in the patient's serum needing a transfusion during antibody detection and identification.[13] The aim of this study is to evaluate the frequency of Rh-and Kell phenotype of voluntary blood donors in Gujarat State, India.

Materials and Methods

This study was conducted at the Department of Immunohematology and Blood Transfusion, B. J. Medical College and Civil Hospital, Ahmedabad.

Sample size

A total of 5670 samples from random voluntary blood donors coming in blood donation camp organized by the Department of IHBT, B. J. Medical College and Civil Hospital, Ahmedabad, India, were collected for extended partial antigen typing during January 2013 to January 2015. Written consent was taken at the time of donor screening. The antigen typing of donors was performed. The objective behind collecting blood samples from different areas was to have representative samples in the study from urban, semi-rural, and rural areas of different zones of Gujarat, India.

Subjects and procedures

A 2.0 ml blood sample was drawn from the antecubital vein of each participant in a tube containing ethylene diamine tetraacetic acid. Rh antigens (D, C, c, E, and e) and Kell (K) were tested by the electromagnetic technology using microplate (Duolys) in a fully automated immunohematology system (Qwalys 3, Manufacturer: Diagast; France).[14] All samples that showed a negative agglutination with anti-D in micro plate (Duolys) were tested again in the antihuman globulin phase with monoclonal antisera (Blend IgG + IgM) by column agglutination technique for the presence of weak “D.”[15]

All donor samples included in the current study were selected only after confirming that their direct antiglobulin test (DAT) results were negative, because if DAT is positive due to IgG coating the cells, typing reagents employing the indirect antiglobulin test may give invalid results.[16]

As a quality control, both Rh control and Coomb's control cells were used to ensure a highly diagnostic sensitivity and specificity, regarding the Rh (D) detection.

Statistical analysis

The Rh and Kell allele frequencies were calculated using the gene counting method, which was described by Mourant et al. in 1976.[17]

Results

A total of 5670 donors were typed during the study period. The most common Rh antigen observed in the study population was e (99.07%), followed by D (95.40%), C (88.77%), c (55.89%), and E (17.88%) [Table 1]. The frequency of the Kell antigen (K) was 1.78% [Figure 1].

Table 1

Comparison of antigen frequencies (in percentage) of our study with North Indian and other ethnic groups

Figure 1

Rh and Kell antigen frequency

The most common Rh phenotype was R1 R1 constituting 43.92% of the whole study population and the rarest was R1Rz (0.035%) [Table 2 and Figure 2].

Table 2

Comparison of phenotypes (%) of our study with North Indian and other ethnic groups

Figure 2

Rh phenotype in our study according Weiner and Fisher-Race nomenclature

Discussion

The antigen frequencies among blood donors from Gujarat were compared with those published for other Indian populations [Table 1]. The frequency of D antigen (95.40%) in our study and North Indian donors was significantly higher than in the Caucasians (85%) and lower than in the Chinese (99%). The frequencies of C, c, and E antigens were dissimilar to other ethnic groups, whereas the e-antigen was present in high frequency in our study as also in the other ethnic groups. The most common Rh phenotype among Caucasians was R1 r (34.9%) and that in Blacks was R0 r (45.8%).

Kell antigen (K) was found in only 101 (1.78%) donors out of 5670. Frequency of Kell antigen in Caucasian and Black populations is 9% and 2%, respectively. The most common Kell phenotype was K-k+, not just in Indians (96.5%), but also in Caucasians (91%), Blacks (98%), and Chinese (100%).

This study found the prevalence of the typed antigens among Indian blood donors to be different to those in the Caucasian, Black, and Chinese populations. This information may be useful to blood transfusion services when deciding on the preventive measures to reduce blood group incompatibility reactions in blood transfusions. Knowledge of the antigen frequencies is important to assess the risk of antibody formation and to guide the probability of finding antigen-negative donor blood, which is especially useful when blood is required for a patient who has multiple red cell alloantibodies, chronic blood transfusion and transfusion in premenopausal women. The results derived in our study were similar to those derived in another study on North Indian population.[18]

Conclusion

It was concluded through our study that most frequent antigen amongst five major antigens of Rh system was Rh “e” (99.07%) whereas the least common was antigen “E” (17.88%). The most common phenotype was DCCee. The most frequent probable genotype was DCe/DCe (R1R1) whereas in Rh negative samples it was dce/dce (rr).

Phenotype and probable genotype showed a wide range of variations in different races and religion. Reliable population-based frequency data of Rh and Kell antigens study has a vital role in population genetic study, in resolving medico-legal issues and most importantly in transfusion practice. More such data are needed to know the trend in population. In situations where clinically significant antibodies are identified in patient's serum, antigen-negative donor units for such cases can be easily retrieved from the donor database of various blood groups available with a blood transfusion center. For this particular reason, all blood banks should have the donor database on antigen frequency of other blood group systems in their local donor population.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.