Rhesus D Variants among Pregnant Women in the Greater Accra Region of Ghana.

Abstract

Background: The rhesus (Rh) blood group system is one of the most polymorphic and immunogenic blood group systems known in humans. The common potent Rh antigens reside on the RH polypeptides. The antigenic expression is controlled by the RHD and RHCE genes, linked in tandem on chromosome 1. The D antigen is clinically the most important because of its high immunogenicity and polymorphism. HDFN is perpetuated by foeto-maternal rhesus antigens incompatibility. Aim: The aim of this study was to identify and classify rhesus D (RH1) variants among pregnant women, that were at a risk of haemolytic disease of the foetus and newborn (HDFN). Methods: This was a cross sectional study involving 110 pregnant women. The RHD status of participants was confirmed using monoclonal antibodies and weak D expression was confirmed by indirect antiglobulin test. Antibody screening was performed using coombs gel cards. RH primers were used to amplify exon 7 which is identical to both RHCcEe and RHD cDNA, and exon 10 that is specific to the D sequence. PCR multiplex assay using six RHD specific primer sets designed to amplify RHD exons 3, 4, 5, 6, 7 and 9 was used for RHD genotyping. Results: All the 110 samples were confirmed as RHD negative by serology. Eight (7.3%) out of the 110 RHD negative samples showed the presence of red cell antibodies in the serum. Thirty four (30%) samples had both exon 7 and 10, depicting an RHD positive phenotype, 67 (60%) samples had only exon 7 amplified, denoting RHD negative phenotype and 9 (8.2%) samples, had neither exon 7 nor 10 denoting indeterminate status. None of the six RHD specific exons were amplified from the 34 D+ and 67 D- individuals. Conclusion: The rate of alloimmunisation was 7.3% that require RHD immunoglobulin prophylaxis. Thirty percent (30%) of the serological RHD negative samples were molecularly RHD positive hence need to be classified as such. This study shows that not all RHD negative pregnant women require anti-D immunoglobulin prophylaxis.