Serologically Weak D-phenotype: Review and Interpretation of Blood Group RhD

Abstract

The Rhesus system is the second most important erythrocyte system for transfusion after ABO. Accurate determination of the Rhesus status of the donor, recipient, pregnant allows to prevent the development of post-transfusion hemolytic complications of the fetus or newborn associated with incompatibility of the blood of the mother and the fetus by D antigen. Generally, determination of the Rhesus affiliation of a person is performed by serological methods using anti-Rhesus reagents with full or incomplete antibodies. However, the results of serological studies are not always clear. Mutations and other effects of the RH gene locus disrupt the production of the normal D antigen and lead to the emergence of numerous varieties of antigen D. The variant of antigen D was described in 1946 and was designated as Du. The study showed that the differences between Du antigen and normal D were quantitative rather than qualitative. The Du antigen was later designated as Dweak - a weak D-antigen or a weak D-phenotype. In the early 1950s, anti-D antibodies were detected in recipients with a weak D-antigen after transfusion with Rh-positive blood and in pregnant women with the Du phenotype during pregnancy and at the birth of a D+ baby. It was suggested that the D antigen was not homogeneous and consisted of numerous partial variants: D1, D2, D3, etc. A complete set of partial variants corresponds to a complete D-antigen. The absence of any of one or more partial factors leads to the appearance of attenuated forms of the D antigen, denoted as Dpartial. People lacking certain partial antigens can produce anti-D antibodies against them. Differentiation of weak D phenotypes has great clinical importance, because transfusion of Rh-erythrocytes to recipients with Dweak and who are actually Rh-positive, has no scientific justification and leads to unjustified consumption of deficient blood and unnecessary immunoprophylaxis of anti-Rh immunoglobulin to pregnant women. International laboratory practice has no unified policy regarding the diagnosis of weak variants of D antigen and the interpretation of the results. Polymerase chain reaction allows to accurately define the Rh status of an individual and to avoid unreasonable transfusions of Rh-negative blood and unnecessary immunoprophylaxis