(P-IG-36) Red Cell Phenotype Genotype Discrepancy Frequencies in England

Background/Case Studies: National Health Service Blood and Transplant (NHSBT) undertake the majority of patient red cell genotype testing in England. Several different genotype tests are available. Low resolution testing may determine only presence or absence of a pertinent single nucleotide variation e.g. RHCE c.676G, resulting in e+, whereas high resolution testing may identify other genetic changes, enabling prediction of e+^var phenotype. Different tests have different blood group coverage. Results, in the form of predicted phenotypes from genotype (hereafter referred to as genotype), are stored within the NHSBT Laboratory Information Management System (LIMS).

Hospitals and NHSBT perform serological red cell phenotype testing (hereafter referred to as phenotype). Only NHSBT phenotype results are stored within the NHSBT LIMS. Some patients have phenotype and genotype results, providing potential for phenotype v genotype discrepancies (PGD).

Study

Design/Methods: Patient records with genotype results were counted and compared to phenotype results stored in NHSBT LIMS.

Results/Findings: A total of 17,234 patient records had at least one genotype result. Of these, 9,789 had at least one phenotype result, enabling 61,269 comparisons. Of these, 1,217 (2.0%) resulted in PGD that indicated conflicting product selection in 938 (9.6%) patients, see Table 1.

Conclusions: PGD that might result in conflicting component selection occur in every blood group analysed. RH05 (e), RH02 (C) and RH01 (D) had the highest rates at 6.5%, 4.4% and 1.6% respectively. This is not surprising given the heterogeneity within the RH system, and the differing ability of tests to determine presence of variant genotypes/phenotypes. It is standard of care in England to provide D, C, E, c, e and K matched red blood cells (RBC) for transfusion dependent patients and to consider genotype testing. The presence of unexplained PGD cause anxiety for staff and transfusion delays for patients, which are known to contribute to increased morbidity and mortality and should therefore be avoided.

In the presence of PGD in D, selecting D- RBC is possible, but places additional strain on a finite resource. Mixed field results in future phenotype testing may prevent electronic issue, in turn increasing delays. Selecting C- RBC in the presence of C+ to C+^var PGD is relatively straightforward due to patients being c+. However, the use of e- RBC in the presence of e+ to e+^var PGD is only straightforward in D+ and E+ patients. It is therefore imperative that PGD are identified at source. This allows sufficient time for those with expert knowledge of relevant assays to work with clinicians, who understand individual patient needs, to determine, in advance of requirement, the most appropriate RBC for transfusion. This reduces pressurised decision making, ensuring timely provision of the best components to the most vulnerable patients.