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 RHCE*C, but all had RHD*DIVa, which encodes partial D and Go(a) . We then tested RBCs from 19 Go(a+) cryopreserved samples (confirmed to have RHD*DIVa) with four anti-C and observed weak variable reactions. RHCE genotyping found all but one of the samples with RHD*DIVa also had RHCE nt 48G>C and 1025C>T, named RHCE*ceTI. Lookback of samples referred for workup and found to have either allele revealed 47 of 55 had both RHD*DIVa and RHCE*ceTI, four had RHD*DIVa without RHCE*ceTI, and four had RHCE*ceTI without RHD*DIVa. Alloanti-c was found in a patient with c+ RBCs and RHCE*ceTI in trans to RHCE*Ce, and alloanti-e was found in a patient with e+ RBC and RHCE*ceTI in trans to RHCE*cE. RHD*DIVa in trans to RHD erroneously tested as RHD hemizygous.

Conclusions: RHD*DIVa and RHCE*ceTI 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. RHCE*ceTI encodes partial c and e antigens. We confirm that RHD zygosity assays are unreliable in samples with RHD*DIVa.