Detection of RhD_el in RhD-negative persons in clinical laboratory

The Rhesus (Rh) blood group is the most polymorphic human blood group system, and it is clinically significant in transfusion medicine. About 15% of Caucasoid people are RhD-negative, whereas in the Asian population, the RhD-negative blood type only occurs in 0.1% to 0.5%. However, approximately 30% of apparently RhD-negative Taiwanese people actually were RhD_el. Traditionally, we verify RhD_el by a serologically adsorption-elution procedure with polyclonal anti-D. In our recent report, RhC phenotype is highly associated with RhD_el, and RHD1227A is a useful genetic marker for RhD_el. For setting up a rapid protocol to detect RhD_el in clinical laboratory, a total number of 395 Taiwanese serological RhD-negative blood samples, those with RhC (+) phenotypes as selected by serological tests, were further screened by adsorption/elution tests and RHD1227A allele by specific sequence primer-polymerase chain reaction (SSP-PCR) for RhD_el. Among 395 blood samples collected from RhD-negative subjects, the incidence of RhC (+) was 43% (171/395). One hundred and twenty six of the 171 RhC (+) samples were positive for both adsorption/elution for RhD detection and SSP-PCR assay for RHD1227A. The sensitivity and specificity were 96.9% and 97.5%, respectively, for RHD1227A detection as compared with the traditional adsorption/elution test. Our results also indicated that RHD1227A was highly linked to Ce haplotypes (95.2%). In conclusion, combined RhC (+) phenotyping and RHD1227A analysis can be a simple and accurate laboratory screening protocol for RhD_el detection in RhD-negative population.

Abbreviations:  Rh, rhesus , SSP-PCR, specific sequence primer-polymerase chain reaction , HDN, hemolytic disease of newborn