High prevalence of serological weak D phenotype and preponderance of weak D type 4.0.1. genetic variant in a Nigerian population: implications for transfusion practice in a resource-limited setting

ABSTRACT Introduction: Prevalence of RhD negative phenotype in Nigeria is low; this leads to scarcity of RhD negative red cells for transfusion. Serological and molecular genotyping of RhD negative individuals for weak D types could reduce this scarcity. The aim of this study was to determine the serological prevalence and molecular types of weak D phenotypes among blood donors and pregnant women in Kano, Nigeria. Methods: A total of 4482 blood donors and pregnant women from three hospitals in Kano were recruited. An indirect antiglobulin test was used to determine weak D phenotypes. Molecular genotyping was performed on genomic DNA from whole blood amplified by polymerase chain reaction sequence-specific primers (PCR-SSP) with agarose gel electrophoresis. Results: The mean age of the participants was 26.50 ±5.79 years. The prevalence of the RhD negative phenotype was 4.2% (189/4482). Of the 189 RhD negative phenotypes, 20 (10.6%) were weak D positive. Molecular genotyping of the 20 Weak D positive phenotypes revealed 15 (75%) weak D type 4, of which 11 were due to the RHD*09.03 and RHD*DAR3 (T201R, F223V) polymorphisms and 4, due to RHD* 08.01 and RHD* DFV polymorphisms; 2 (10%) were due to the 602 C>G polymorphism, while the remaining 3 (15%) constituted partial D or other rare weak D types. Conclusion: The prevalence of weak D positive phenotypes is high in this study; weak D type 4 is the most common RhD genetic variant. Routine serologic weak D testing of RhD negative blood and molecular genotyping should be encouraged in resource-limited settings.

Identification of pregnant women with DFR genotype and discussion of prenatal examination strategy / 中国输血杂志

【Objective】 To identify three cases of pregnant women with the D variant phenotype using serological and molecular tests, and discuss the strategy of prenatal examination. 【Methods】 The peripheral blood samples from three pregnant women with the D variant phenotype were collected. RhD variant phenotype was determined using routine serological methods with two different kinds of monoclonal anti-D. The serological characteristic for the epitope of D antigen was further analyzed using the commercial panel anti-D reagents (D-Screen, Diagast). The hybrid RHD-CE-D allele was analyzed by the Multiplex Ligation-dependent Probe Amplification (MLPA) assay and polymerase chain reaction with sequence specific primers (PCR-SSP) method. Further Sanger sequencing of RHD gene exons was also performed. 【Results】 DFR phenotype was primarily determined by serological characteristic for the epitope of D antigen. RHD*DFR2/01N.01(n=2) and RHD*DFR1/1227A(n=1) genotypes were identified by the MLPA assay, PCR-SSP and Sanger sequencing. 【Conclusion】 Two pregnant women with RHD*DFR2/01N.01 genotype should be treated as D negative patients clinically, while the pregnant woman with RHD*DFR1/1227A genotype can be treated as Asia type DEL to avoid unnecessary antibody screening and anti-D prophylaxis.