Rhtyping

Rhtyping, commonly spelled Rh typing in medical literature, is the laboratory process used to determine whether red blood cells express the Rh(D) antigen. The result informs whether blood is Rh positive or Rh negative and is routinely performed for blood transfusion compatibility and management during pregnancy.

The Rh blood group system was identified in the 1940s by Karl Landsteiner and Alexander Wiener, who showed that certain antibodies react with red cells bearing specific antigens. Rh typing became standard practice after the discovery of the D antigen, which is a major determinant of Rh status.

Methods include serologic typing, which uses anti-D antibodies to detect the presence of the D antigen on red cells. Classical methods include tube agglutination and microplate assays, while gel card techniques and solid-phase assays offer automation and higher sensitivity. Flow cytometry can measure low densities of D antigen, and molecular typing analyzes the presence and structure of the RHD gene to predict Rh status, especially in cases with weak or variant expression.

Applications of Rh typing are essential for safe transfusion practices, ensuring compatibility between donor and recipient. In obstetrics, Rh typing guides prenatal risk assessment for hemolytic disease of the fetus and newborn and determines the need for Rh immune globulin prophylaxis.

Limitations: Some individuals express weak or variant D antigens, which can complicate typing and require confirmatory testing. Ongoing improvements in standardization and molecular methods aim to reduce discordant results.