Abstract:

The Rh blood grouping system is a critical standardized test in transfusion medicine, especially for the cases related to haemolytic transfusion reactions and neonatal haemolytic disease caused by clinical RhD blood group incompatibility. In the present case report, we presented two cases with the uncommon RHD gene variation RHD*DEL37. The blood samples of the two subjects were mistakenly identified as RhD-negative through conventional serological testing. Firstly, both blood samples were tested negative for the RhD antigen using traditional tube test and gel microcolumn methods. The phenotyping of RhCE were identified as ccEe and ccee for each sample, respectively. Secondly, genetic analysis was performed using polymerase chain reaction-sequence specific prime (PCR-SSP) which revealed that neither sample belonging to the several common RHD gene variants which was found in Asia. Moreover, they turned out to be positive for the RHD haplotype, which indicated that exons 1-10 on one of the RHD alleles were entirely absent. In addition, a T>C mutation was observed at bases 1154-31 in intron 8 of the other allele, which was located at the intron 8 breakpoint. This result was obtained after further Sanger sequencing of exons 1-10 of the RHD gene. The mutant allele was designated as RHD*DEL37 by the International Society of Blood Transfusion (ISBT) and was identified as D-elute(D^el) by phenotype ana-lysis. Both samples were genotyped as RHD*DEL37 and showed positive results. In summary, the true genotype of the two blood samples, of which the screening results only using serological testing method was negative, were RHD*DEL37 /RHD-(RHD*01N.01). Notably, this kind of genotype was reported for the first time in Chinese population. Moreover, the two individuals did not have ties of consanguinity, indicating that some of the Chinese individuals could be carriers of the genetic mutation. Therefore, it might be necessary to further confirm the frequency of this mutation in the Chinese population and the possibility of homozygosity for this mutation. This report identifies infrequent RHD gene mutation samples by coupling molecular biology and serological methods to prevent misclassification of blood groups. Combining serological and molecular biology test results to determine blood group is critical in protecting patients during clinical transfusion procedures.

Key words: Rh-Hr blood-group system, Serology, Genotyping techniques, Alleles