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.

Detection of Hpdel among Thais, a deleted allele of the haptoglobin gene that causes congenital haptoglobin deficiency.

BACKGROUND: Congenital haptoglobin deficiency is a risk factor for anaphylactic nonhemolytic transfusion reactions in Japan. The deleted allele of the haptoglobin gene, Hp(del), which causes congenital haptoglobin deficiency, has also been observed in other Northeast Asian populations, such as Korean and Chinese persons. It has not been reported in several African and European-African populations, however, or investigated in other countries. STUDY DESIGN AND METHODS: To investigate the distribution of congenital haptoglobin deficiency in Southeast Asian countries, blood samples collected from 200 randomly selected healthy Thai volunteers were analyzed for serum haptoglobin and the haptoglobin gene. Plasma haptoglobin concentration was measured to identify haptoglobin deficiency. Haptoglobin phenotyping was performed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Western blotting. The presence of the Hp(del) allele was determined with genomic DNA by an Hp(del)-specific polymerase chain reaction (PCR) method. RESULTS: There were no haptoglobin-deficient subjects detected among the 200 Thais. Their haptoglobin phenotypes were as follows: Hp 1-1 in 10, Hp 2-1 in 81, and Hp 2-2 in 109. Six individuals heterozygous for Hp(del) were detected. The frequency of the Hp(del) allele was calculated to be 0.015. The prevalence of haptoglobin deficiency caused by Hp(del) homozygosity was estimated to be approximately 1 in 4000. CONCLUSION: Congenital haptoglobin deficiency caused by Hp(del) homozygosity is presumed to be present in Thailand as a risk factor for anaphylactic transfusion reactions with a frequency similar to that in Japan. The causative deleted allele of the haptoglobin gene, Hp(del), is distributed among Southeast Asian populations as well as among Northeast Asian populations.