RHCE*ceTI encodes partial c and partial e and is often in cis to RHD*DIVa.

BACKGROUND

In the Rh blood group system, variant RhD and RhCE express several partial antigens. We investigated RH in samples with partial DIVa that demonstrated weak and variable reactivity with anti-C.

STUDY DESIGN AND METHODS

Standard hemagglutination techniques, polymerase chain reaction-based assays, and RH sequencing were used.

RESULTS

DNA analysis showed that six red blood cell (RBC) samples with weak and inconsistent reactivity with anti-C lacked RHCEC, but all had RHDDIVa, which encodes partial D and Go(a) . We then tested RBCs from 19 Go(a+) cryopreserved samples (confirmed to have RHDDIVa) with four anti-C and observed weak variable reactions. RHCE genotyping found all but one of the samples with RHDDIVa also had RHCE nt 48G>C and 1025C>T, named RHCEceTI. Lookback of samples referred for workup and found to have either allele revealed 47 of 55 had both RHDDIVa and RHCEceTI, four had RHDDIVa without RHCEceTI, and four had RHCEceTI without RHDDIVa. Alloanti-c was found in a patient with c+ RBCs and RHCEceTI in trans to RHCECe, and alloanti-e was found in a patient with e+ RBC and RHCEceTI in trans to RHCEcE. RHDDIVa in trans to RHD erroneously tested as RHD hemizygous.

CONCLUSIONS

RHDDIVa and RHCEceTI almost always, but not invariably, travel together. This haplotype is found in people of African ancestry and the RBCs can demonstrate aberrant reactivity with anti-C. RHCEceTI encodes partial c and e antigens. We confirm that RHD zygosity assays are unreliable in samples with RHDDIVa.