Eluted blood group antigens: A diagnostic challenge in red cell antibody identification – A case series

Background Accurate red cell antibody identification is central to immunohematology, yet reagent red cell variability can compromise test reliability. Factors such as manufacturing differences, reagent composition, and cold-chain instability may alter assay sensitivity and obscure result interpretation. This study, for the first time, reports elution of Lewis antigens from reagent red cell panels, highlighting its role in antibody identification errors and diagnostic ambiguity. Materials and methods Over one year, five cases with inconclusive antibody identification due to reagent variability were analyzed. Comprehensive immunohematology workup was performed using commercially available panels. Root cause analysis, including Ishikawa chart evaluation, examined patient, technical, external, and reagent-related factors. Retesting was done with panels from an alternate manufacturer, and papain-treated reagent cells were assessed for antigenic alterations. Results Panels from Manufacturer 1 yielded atypical, non-specific reactions. Retesting with Manufacturer 2’s panels identified anti-Leᵃ and/or anti-Leᵇ antibodies in all cases. Phenotyping showed absence of Leᵃ and Leᵇ antigens on reagent cells 4–6, contrary to their antigram, leading to false-negative reactions. Papain treatment did not affect reactivity, confirming Lewis antigen loss as the root cause of misidentification. Conclusion Lewis antigen expression on reagent red cells should be routinely verified, as these plasma-derived antigens may dissociate under variable conditions. Incorporating this check into quality control protocols can enhance assay reliability, reduce diagnostic errors, and improve turnaround time.