The expression of the Duffy Antigen/Receptor for Chemokines (DARC) on red blood cells (RBC) has been commonly determined using hemagglutination tests. Because the vast majority of African individuals are Duffy-negative, screening for DARC expression on RBC is a valuable tool to assess Caucasian admixture in populations of African descent. Furthermore, blood group antigens have been frequently rested as potential risk factors for complex diseases. We established a dot-blotting protocol using sequence-specific oligonucleotides (SSOs) for tile DARC-46T ('Duffy-positive') and -46C ('Duffy-negative') alleles. With this method, but nor with serological methods, Duffy-positive individuals can be further characterized as homozygous or heterozygous for the dominant Duffy-positive allele, allowing more precise estimation of allele frequencies anti admixture in heterogeneous populations. In unrelated African American (n = 235), Afro-Caribbean (n = 90) and Colombian (n = 93) subjects, the frequency of the -46T allele was 21.7%, 12.2% and 74.7%, respectively. The percentage of Duffy-positive individuals (homozygous or heterozygous for the -46T allele) in each population was in accordance with published frequencies. As expected, the -46C allele was nor detected in 20 Caucasian subjects. This sensitive and specific method allows for the rapid and inexpensive screening of large samples for Duffy genotypes using small quantities of genomic DNA.
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We thank all families in Cartagena, Barbados, and the USA for their generous participation in this study; we are grateful to Maria Stockton, Lun Xue, Beverly Plunkett and Eva Ehrlich for excellent technical support. We thank all members of the CSGA for their contribution to this project. This work was supported by NIH Grants A1-40274, HL/A1-49612, HL/AI-49596, HL/A1-49609, and HL/A1-49602.