How is Rhesus (Rh) typing performed?

Updated: Aug 01, 2018
  • Author: Victoria K Gonsorcik, DO; Chief Editor: Jun Teruya, MD, DSc, FCAP  more...
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Answer

Answer

Rh(D) typing is usually performed at the time of ABO typing and antibody screening. A blood sample is placed in a centrifuge, which separates the red blood cells from the plasma. The individual's red cells are diluted to make a working suspension (2%-5%) in saline. The red cell suspensions are then mixed with anti-D reagent.

The test is used to measure visual agglutination or lack of agglutination. Agglutination refers to the clumping of cells in the presence of antibody. Unlike ABO typing, a "reverse" test is not performed, because a person should not have preformed antibodies to the D antigen, unless they have previously been alloimmunized to the D antigen through transfusion or pregnancy. [3]

Traditionally, blood typing used serologic testing, based on hemagglutination reactions against specific antisera; more recently, molecular typing, based on detecting the polymorphisms and mutations controlling the expression of blood group antigens, has been used as an alternative or supplemental typing method. [2]


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