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Miscellaneous Causes of ABO Discrepancies

Miscellaneous problems may cause ABO discrepancies, including:
  • Cold reacting autoantibodies that result in spontaneous RBC agglutination or a positive direct antiglobulin test (DAT)
  • Mixed red blood cell populations due to massive transfusion
  • Unexpected alloantibodies unrelated to ABO antigens
  • Unexpected ABO isoagglutinins

Examples of Group IV Miscellaneous Discrepancies:
  • Group AB patient massively transfused with type O donor units
    • Mixed field agglutination in the forward type can occur in subsequent patient samples
  • Cold reacting autoanti-I, coating patient red blood cells
    • Sensitized patient red blood cells could cause discrepancy in the forward type
  • Cold reacting alloantibody such as anti-M
    • The prevalence of the M antigen could result in detection on either the A1 or B cells in the reverse type.
  • The stimulation of anti-A1 formation in the plasma of patient with a subgroup of A
    • This can happen as a result of exposure to donor red cells or through pregnancy.