Background: This study is a comprehensive analysis of RHD in D-negative phenotypes in saline, in Xi'an, Shanxi province, central China.
Material and methods: DCcEe in saline was measured for each blood sample from every donor between January 2008 and June 2012 in the Xi'an Blood Centre, China. D-negative results were confirmed by an indirect antiglobulin test and further investigated by adsorption-elution as required. The initial step of molecular analysis was RHD zygosity testing. Then RHD was detected by a sequence-specific polymerase chain reaction system for RHD(1227G>A), weak D type 15, and RHD(711delC) alleles for the samples carrying at least one RHD. For the remaining non-identified samples, ten RHD exons were amplified using a previously widely used RHD coding region sequencing method. Some RHD/RHCE conversion alleles were identified while those remaining were submitted to direct sequencing.
Results: Overall, 2,493 D-negative samples in saline were detected in a total of 890,403 donors (D-negative rate, 0.28%). Among the D-negative individuals, RHD deletion (d/d) was assessed in 1685 donors (67.59%). Non-functional RHD alleles were detected in 184 donors (7.38%), the most common being the RHD-CE(2-9)-RHD and RHD(711delC) alleles. Two new alleles were observed and family investigations were performed; RHD(1227G>A) DEL was detected in 516 individuals (20.70%), and weak D or partial D variants were identified in 108 donors (4.33%). The most common alleles were weak D type 15, D(VI) type 3 and D(V) type 2. Four new weak D alleles were noted, and two cases of RHD(1227G>A)/weak D type 15 heterozygosity were confirmed.
Conclusions: Currently, it seems to be difficult to observe any new RHD alleles in the Han Chinese population. D prediction in this population is easier because popular alleles are dominant, accounting for about 99.80% of alleles in D-negative people. Weak D types and partial D variants are rare and occur in approximately 0.01% of the population.