Frequencies of Duffy blood group alleles in Northern Pakistani donors

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Abstract

Objective

Find the allele frequencies of Duffy blood group antigens in donor population from northern Pakistan.

Place and Duration of Study

Armed Forces Institute of Transfusion (AFIT), Rawalpindi in year 2012.

Patients and Methods

A total of 1000 healthy, adult blood donors were included in the study. Blood samples were collected in ethylenediamine tetra aceticacid (EDTA) tube and then tested with anti sera Fya and Fyb by the tube method.

Results:

 The allele frequencies of Duffy blood group antigens were calculated. The most common phenotype was Fy(a+b+) which was present in 552 (55.2%) donors followed by the Fy(a+b-) phenotype in 228 (22.8%) donors, while 178 (17.8%) were Fy(a-b+) and the least prevalent phenotype was Fy(a-b-) which was present in 42 (4.2%) of donors.

Conclusion

The majority of our population is heterozygous for Duffy antigens a and b.

Introduction

Duffy (Fy) blood group antigens are glycoprotein receptors on blood cells that act as a receptor for chemokines and for plasmodium vivax invasion. Red blood cells that lack Duffy antigens are resistant to plasmodium vivax invasion [1].

The Duffy blood group was first identified in 1950 in a patient with haemophilia who developed anti-Fya after multiple transfusions [2]. Anti-Fyb was discovered in multiparous woman after 1 year. Later the remaining antigens were discovered 20 years later. Six antigens are included in the Duffy blood group system; however, Fya and Fyb antigens are clinically the most important. The Fy gene is located on chromosome 1, and is comprised of two exons and is inherited as co dominant alleles therefore both antigens can be expressed in one individual [3]. Fya and Fyb antigens differ only by a single amino acid. The Duffy blood group has four major phenotypes, Fy(a+b+), Fy(a+b-), Fy(a-b+) and Fy(a-b-) [4]. The Duffy null phenotype has the Fyb allele with a mutation in the promoter region which abolishes the expression of the protein in erythrocytes only [5].

Antibodies against the Duffy antigen are usually of the IgG type and can cause hemolytic transfusion reactions, mostly the delayed type which range from mild to severe in nature. Anti-Fya can cause mild hemolytic disease of the newborn while anti-Fyb is rare [6].

The frequency of Duffy phenotype varies in different geographical areas and its geographical distribution is of extreme interest to the malariologist, because the Duffy antigen act as a receptor for plasmodium vivax [7]. The Duffy null phenotype is common in Africans as a result of population selection, hence there is little plasmodium vivax malaria in Africa [8]. However in Asia plasmodium vivax is the most common cause of malaria due to the rarity of the Duffy null phenotype.

The frequency of the Duffy antigen has not been previously reported in the Pakistani population, therefore this study was undertaken. These data can be used to calculate the population at risk for plasmodium vivax infection [9]. Also, these data can be useful for blood banks to find antigen negative blood for alloimmunized patients and for the preparation of indigenous cell panels.

Section snippets

Methods

A total of 1000 donors from northern areas of Pakistan donating blood at AFIT, between 18 to 60 years were randomly selected for red cell Fy antigen typing and calculation of allele frequency. It included Fya and Fyb antigen typing. A 2 ml sample of blood was drawn from antecubital vein of each donor in a disposable syringe and transferred immediately to a tube containing EDTA. Duffy blood group detection was done by tube method using commercially prepared anti-sera of Fya and Fyb (LORNE UK) by

Results

Out of 1000 healthy blood donors, the most common Duffy phenotype in Pakistanis was Fy(a+b+) which was present in 552 (55.2%) donors, followed by 228 (22.8%) donors having the Fy(a+b-) phenotype, 178 (17.8%) donors were Fy(a-b+) and only 42 (4.2%) were Fy(a-b-). The allele frequency of Fya and Fyb antigen were 50.4% and 45.4% respectively calculated from the Fy blood group phenotype prevalence as shown in Table 1.

The Hardy–Weinberg equation was applied to calculate the frequency of three

Discussion

Blood group distributions are different and distinctive for population groups, and can show noticeable geographic prevalence around the world. Global incidence of the Duffy blood group was always of interest to transfusion centers but also of particular significance to malariologists as Duffy-negative phenotype provide resistance against Plasmodium vivax infection [11]. The Duffy blood group is one of the most commonly investigated blood groups around the world. It has a characteristic

Conclusion

This study has documented allele frequency of Duffy blood group antigens in donor population of Northern Pakistan. We have compared our data with Caucasians, Blacks and Indian population and found that the frequencies in our population resemble Caucasians. The data are useful not only for preparing indigenous screening cells but also to create a donor data bank and finding compatible blood for alloimmunized patients.

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