A novel reagent for the screening of haptoglobin‐deficient blood donors

Background and Objectives In Japan, the prevalence of haptoglobin deficiency is approximately 1 in 4000. Haptoglobin‐deficient individuals may produce anti‐haptoglobin from allo‐immunization, leading to serious transfusion reactions. Therefore, implementation of a consistent supply of haptoglobin‐deficient fresh frozen plasma is crucial. We developed a novel reagent to facilitate large‐scale identification of haptoglobin‐deficient individuals as potential donors of plasma products. Materials and Methods We established mouse monoclonal anti‐haptoglobin‐producing cell lines (three clones) using the hybridoma method by immunizing mice with the haptoglobin protein. Purified antibodies were conjugated with carboxylate‐modified polystyrene latex beads and used for haptoglobin measurements by the latex agglutination method using an automatic analyser (LABOSPECT008). Samples with low protein concentrations were re‐examined by enzyme‐linked immunosorbent assay to confirm the results. Additionally, the haptoglobin gene was amplified by polymerase chain reaction to confirm the haptoglobin deletion allele (Hpdel). Results From February to October 2022, 7476 blood donor samples were screened. Two haptoglobin‐deficient and 21 low‐haptoglobin‐expressing individuals were identified. Two haptoglobin‐deficient donors were found homozygous for Hpdel, and 19 (90%) of the 21 low‐haptoglobin‐expressing individuals were heterozygous for Hpdel, which includes the first reported case of heterozygous Hpdel/HpJohnson. Conclusion We developed a new reagent for the detection of haptoglobin deficiency, which is automatable and inexpensive and appears useful for large‐scale screening of blood donors.