LifeShare Blood Center Shreveport, Louisiana, United States
Background/Case Studies: Samples from a previously transfused, 78 yr. old Caucasian female with a history of a cold autoantibody (CAA) were submitted to the Immunohematology Reference Laboratory for ABO resolution and antibody identification.
Study
Design/Methods: Serologic evaluation included a standard ABO discrepancy investigation, a full RBC phenotype with licensed antisera, tube testing at all phases with low ionic strength solution (LISSTM) and polyethylene glycol (PeGTM) enhancements (Immucor, Inc., Norcross, GA), allogeneic adsorptions and elution studies (Gamma ELU-KIT® II (Immucor, Inc, Norcross, GA)). Extended testing phases included immediate spin (IS), 5-minute (min) room temperature (RT), 10-min RT with LISS, 30-min 37C with LISS and anti-human globulin (AHG). Additional testing was performed with 15-min 37C PEG and AHG. The adsorbed serum was tested with no enhancement at IS, 10-min RT, 30-min 37C and AHG.
Results/Findings: The previously identified CAA was no longer detectable but an ABO discrepancy was present. Historical records indicated the patient is group A yet additional reactivity was present in the reverse type. Current phenotyping predicts the patient is R1R1 with an anti-E present at AHG with PeGTM. An apparent anti-CE was also demonstrated at all phases (preferentially at IS and RT, weaker at 37C and AHG) with LISSTM and at AHG with PeGTM. The auto-control was weakly reactive at IS only. The DAT was microscopically reactive with anti-C3 and negative with anti-IgG. An allogeneic adsorption was performed using patient serum and untreated, intact group O R2R2 cells. The anti-E was successfully removed and the anti-CE confirmed in the adsorbed serum. Anti-E was identified in the eluate prepared from the R2R2 adsorbing cells. The ABO discrepancy was resolved using E negative reverse grouping cells. Conclusions: CE (RH22) is a compound antigen where C and E are present on the same RhCE protein and must be in cis for its expression. The CE haplotype has a reported prevalence of 2% in Asians and < 1% in most populations. The two previously reported examples of anti-CE were found in the presence of anti-C and were likely naturally occurring. Like the historical examples, this anti-CE appears to be naturally occurring; however, it is possible the patient was sensitized from previous transfusion. Unfortunately, the units had not been antigen typed for C or E and there have been no subsequent donations. Unique to this case is the presence of the anti-E rather than anti-C in the sera. The low frequency of the CE haplotype may contribute to the low incidence of anti-CE as risk of sensitization from donor units is low. Although the clinical significance of anti-CE is unknown, the antibody reacts preferentially at RT and 37˚C. If transfusion is required, CE-negative, AHG crossmatch compatible units should be given.
