RhStatus

RhStatus is a term used to describe an individual's Rhesus (Rh) blood group status, specifically the presence or absence of the RhD antigen on red blood cells. Determining RhStatus is essential for safe blood transfusions and for managing pregnancy, where incompatibility between an Rh-negative mother and an Rh-positive fetus can cause immune-mediated hemolysis.

Testing methods include serologic typing, which uses antibodies to detect the RhD antigen on red cells, and include forward typing (cell-based) and sometimes reverse typing. Some individuals express weak or variant forms of RhD that require enhanced testing (weak D testing) to avoid misclassification. Molecular techniques, such as RHD gene genotyping, can identify deletions, insertions, or variant alleles that affect antigen expression and can resolve discordant results.

Applications: In transfusion medicine, RhStatus informs donor-recipient compatibility to prevent alloimmunization. In obstetrics, RhStatus determines the need for preventive treatment with anti-D immune globulin to Rh-negative pregnant people carrying Rh-positive fetuses, reducing the risk of hemolytic disease of the fetus and newborn (HDFN).

Limitations and variability: Rare Rh variants, placental or sample issues, and laboratory differences can lead to discordant results. Some settings rely on reflex genotyping for confirmation. Access to testing and interpretation may vary by region.

History and standards: The Rh system was identified in the early 1940s, with the RhD antigen later recognized as the primary clinically relevant determinant. Modern practices follow international and national guidelines from bodies such as the World Health Organization and transfusion medicine organizations, harmonizing serologic and genetic testing to determine RhStatus.