title: Serologic and molecular characterization of D variants in Brazilians: impact for typing and transfusion strategy.
abstract: Rh discrepancies are a problem during routine testing because of partial D or weak D phenotypes. Panels of monoclonal antibodies (MoAb) are being developed to identify D variants such as partial D and weak D when there are anomalous D typing results; however, molecular characterization offers a more specific classification of weak and partial D. The weak D and partial D phenotypes are caused by many different RHD alleles encoding aberrant D proteins, resulting in distinct serologic phenotypes and the possibility of anti-D immunization. We evaluated currently used serologic methods and reagents to detect and identify D variants and correlated the results with molecular analyses. A total of 306 blood samples from Brazilian blood donors and patients with discrepant results in routine D typing were analyzed. In total, 166 (54.2%) weak D, 136 (44.4%) partial D, 3 (1%) DEL, and 1 (0.3%) DHAR variants were identified. Among weak D samples, 76 weak D type 1 (45.8%), 75 weak D type 2 (45.2%), 13 weak D type 3 (7.8%), and 2 weak D type 5 (1.2%) alleles were found. Among the partial D samples, 49 type 4.0 weak partial D (36%), 9 DAR (6.6%), 24 DFR (17.6%), 6 DBT (4.4%), 1 DHMi (0.73%), 26 DVI (19%), 14 DVa (10.3%), 5 DIVb (3.7%), and 2 DVII (1.5%) were observed. Two samples identified as DEL by adsorption-elution were characterized by molecular analyses as RHD(IVS5–38DEL4) and one sample was characterized as RHD(K409K). One sample was characterized as DHAR, a CE variant positive with some monoclonal anti-D. Our results showed that the use of different methods and anti-D reagents in the serologic routine analysis revealed D variants that can be further investigated. Molecular methods can help to differentiate between partial D and weak D and to characterize the weak D types, providing additional information of value in the determination of D phenotypes. This distinction is important for optimized management of D– RBC units and for the prevention of anti-D–related hemolytic disease of the fetus and newborn.
authors.affiliation: Instituto Nacional de Ciência e Tecnologia do Sangue, Hemocentro, UNICAMP, Rua Carlos Chagas, 480, Caixa Postal 6198, CEP 13081-970 Barão Geraldo, Campinas, SP, Brazil.
authors.forename: Débora Castilho
authors.initials: DC
authors.lastname: Credidio
authors.forename: Jordão
authors.initials: J
authors.lastname: Pellegrino
authors.forename: Lilian
authors.initials: L
authors.lastname: Castilho
mesh_terms: D001782:Blood Donors; D001788:Blood Grouping and Crossmatching / Q000379:methods* / Q000592:standards; D001803:Blood Transfusion; D001938:Brazil; D004252:DNA Mutational Analysis; D005787:Gene Frequency; D006801:Humans; D007518:Isoantibodies / Q000097:blood; D009154:Mutation / Q000235:genetics; D011110:Polymorphism, Genetic; D011485:Protein Binding; D012203:Rh Isoimmunization / Q000235:genetics / Q000276:immunology; D012204:Rh-Hr Blood-Group System / Q000235:genetics* / Q000276:immunology*
chemical_list: D007518:Isoantibodies; D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen