El Grupo Rh De La Sangre

CHAPTER

10
THE Rh BLOOD GROUP SYSTEM
CONNIE WESTHOFF

OBJECTIVES
After completion of this chapter, the reader will be able to: 1. Describe the Rh system antigens, including: a. The allelesinherited at each locus. b. The causes of weak D and partial D expression. c. Variations in C and e antigen expression. d. Compound antigens. e. How to determine an individual’s most probable genotype.2. Discuss causes of the Rhnull phenotype. 3. Describe Rh system antibody reactivity and characteristics. 4. Discuss the administration of Rh immune globulin. 5. Describe the reagents used in Rhtyping and the appropriate controls. 6. List causes of discrepancies in Rh typing.

KEY WORDS
Compound antigen Deleted or partially deleted phenotype Fisher and Race G antigen ISBT Partial D Rhhaplotype Rh immune globulin Rh negative Rh positive Rhnull Weak D Wiener terminology

he Rh blood group system is one of the most polymorphic and antigenic blood group systems. It is second only to ABO inimportance in blood transfusion and is well known as a primary cause of hemolytic disease of the fetus and newborn (HDFN). The principal antigen is D, and the terms Rh positive and Rh negative referto the presence or absence of D antigen. Caucasians of European extraction have the highest incidence of the Rh-negative phenotype (15% to 17%), and Rh-negative type is much less common in Africa (5%)and Australia and is considered a rare blood type not routinely tested for in some parts of Asia ( 1%). Other common Rh antigens include the antithetical C and c, and E and e antigens. Patients arenot routinely typed for these unless they have developed atypical antibodies or are facing long-term transfusion support for diseases such as myelodysplasia or sickle cell disease (SCD). In addition tothe five principal antigens (D, C, c, E, and e), more than 50 other Rh system antigens are known. Because they are not often encountered in the routine blood bank, they will not be covered here in...