COOMBS TEST

• Rh blood group system


  2nd most important blood group system, next to ABO blood group system
• Rh blood group system

  • A significant cause of Hemolytic Transfusion Reaction (HTR) and primary cause of Hemolytic Disease of the Fetus and the Newborn (HDFN)
  • More complex compared with the ABO system because it is made up of more than 50 antigens
• ISBT no. 004 (it is the 4th discovered blood group system after ABO, MNS, and P1PK system)
• Major antigens of the Rh system


  • D
  • C
  • c
  • E
  • e
• Rh blood group system discovered by Levine and Stetson


  1939
• Rh antibody or Rhesus antibody


  Named in 1940 by Landsteiner and Wiener after discovering that the antibody isolated in 1939 can agglutinate Rhesus macaque monkey red cells
• Years after the discovery of the Rh blood group system, other scientists have discovered that although similar, the antibody produced by this woman in 1939 is different from the antibody produced by the guinea pig of Landsteiner and Wiener
• Rh (+)


  There is the presence of D antigen on RBC
• Rh (-)


  There is the absence of D antigen on RBC
• Only the presence or absence of the "D" antigen will determine the Rh type
• The presence or absence of the C/c and E/e antigens has nothing to do whether a person is Rh (+) or Rh (-)
• Anti-D antisera


  Antisera used to determine the presence of D antigen
• There is no "d" antigen in the Rh BGS
• Small letter "d"


  Means the absence of the big "D" antigen
• Fisher-Race terminology


  Also known as DCE Nomenclature, uses the letters DCE when naming the genes and antigens of the Rh BGS
• Fisher-Race terminology


  • Each Rh genes are inherited from each parent as a set of 3 closely linked set of alleles
  • Rh genes are inherited via codominant pattern of inheritance
• Gene frequencies in Rh blood group system

  • D (Rh positive): 85%
  • d (Rh negative): 15%
  • C: 70%
  • E: 30%
  • c: 80%
  • e: 98%
• Rh positive is more frequent (85%) than that Rh negative (15%)
• Among Filipinos, Rh positive is more frequent and predominant than Rh negative
• Some Europeans and Africans are Rh negative
• The rest of the people all over the world are Rh positive
• Most common antigen may be encountered is the "e" antigen since 98% of the population will inherit the "e" gene
• Rh null phenotype


  No inherited gene from the Rh blood group system
• Rh genotypes


  • DCE/dcE
  • dce/dCE
  • Dd (Heterozygous Rh (+) Father and Rh (-) Mother)
  • DD/Dd (Heterozygous Rh (+) Father and Heterozygous Rh (+) Mother)
  • DD/Dd (Homozygous Rh (+) Father and Heterozygous Rh (+) Mother)
• Wiener terminology


  Also known as Rh-Hr nomenclature, uses the letters Rh-Hr to refer to the genes and antigens of the Rh blood group system
• Wiener terminology


  • Each Rh gene that we inherit from our parents encodes for an agglutinogen that contain a series of 3 blood factors/antigens
  • The product of genes in Wiener Terminology is the agglutinogen, but the agglutinogen produced are three blood factors
• Conversion between Fisher-Race and Wiener terminology


  • D = Factor Rh0
  • d = -
  • C = Factor rh'
  • c = Factor hr'
  • E = Factor rh"
  • e = Factor hr"
• Rosenfield and Coworkers terminology

  Also known as Alpha-Numeric Nomenclature, uses letters and numbers to name the genes and antigens of the Rh System
• Rosenfield and Coworkers terminology


  • Rh1: D
  • Rh3: E
  • Rh5: e
  • Rh2: C
  • Rh4: c
  • Rh6: f
• ISBT terminology


  Also known as Numeric Nomenclature, uses 6-digit number to refer to red cell antigens
• ISBT terminology


  • 004001: D
  • 004003: E
  • 004005: e
  • 004002: C
  • 004004: c
  • 004006: f
• Immunogenicity of Rh antigens

  • D: The most immunogenic
  • e: The least immunogenic
• Never transfuse an Rh positive blood to a Rh negative patient because exposure of an Rh negative person to the D antigen will instantly and effectively stimulate the production of the anti-D antibody among those Rh negative individuals
• This is the reason why HDN is severe between an Rh negative Mother and Rh positive Fetus
• Advantage


  Can name all the 55 antigens of the Rh System and can also name future RH antigens
• Fisher-race & Wiener


  Can describe the genetic or inheritance of Rh genes and antigens
• Rosenfield & ISBT


  Usage of numbers is suitable for computer/electronic crossmatch (no numbers can be replaced because number are infinite)
• The genes or antigens do not describe the genetics of Rh antigens
• Rh antigens in order of immunogenicity


  • D
  • c
  • E
  • C
  • e
• D


  The most immunogenic of all the Rh antigens