reverse typing

• Naturally occurring antibodies


  Individuals possess antibodies directed against the antigens that are absent from their own cells
• Stimuli for Anti-A and Anti-B production

  • Bacteria, pollen, or other substances
• Relationship between antigens and antibodies in the ABO system

  Permits the use of both serum and cell tests in ABO grouping
• Antibody titer development

  1. Initiated at birth

  2. Titer usually too low for serologic detection; increases until the age of 3-6 months

  3. Maternal in origin among newborn and young infants (IgG- maternal transfer)

  4. Anti-A and Anti-B titer decreases with age
• Agglutination of saline suspended erythrocytes

  • Reactivity at room temperature
  • Production of hemolysis in vivo and in vitro
  • Both IgG anti-A and anti-B are capable of binding complement
• Principle of reverse typing

  1. Based on the presence or absence of the antibodies, anti-A and anti-B, in serum

  2. If antibodies are present, agglutination should be demonstrated when combined with reagent erythrocytes expressing A or B antigens
• Test is not definitive for ABO grouping
• Specimens with weak reactions in ABO grouping

  • Newborns
  • Very young infants
  • Elderly patients
  • Patients with immune disorders
• Agglutination in any tube of RBCs test or hemolysis/agglutination in serum tests constitutes positive results
• Smooth suspension of RBCs after resuspension is a negative result
• False positive results causes
• False negative results causes
• Missing/Weak Antigens
• Causes of False Positive Results
• Causes of False Negative Results
• Possible reasons for serum: cell ratio issues

  • Under centrifugation or incorrect incubation temperature
  • Old or otherwise inactive reagents
  • Incorrect interpretation or an error in the recording of test results
• Causes of Missing/Weak Antigens


  • Sub groups A or B antigens may be weakly expressed due to an unusual genotype
  • Disease conditions like acute leukemia can greatly depress red cell antigens in the ABO system
  • Additives to sera like acriflavine can produce false agglutination
  • Mixtures of blood in recently transfused patients or recipients of bone marrow transplants can lead to unexpected reactions
• Resolution for Missing/Weak Antigens

  1. Investigating the possibility of subgroups of A and B

  2. Investigating the diagnosis

  3. Washing the patient’s red cells in saline

  4. Acidifying the anti-B reagent

  5. Washing the patient’s cells and regrouping if dye is suspected or using dye-free reagents
• Causes of Missing/Weak Reacting Antibodies

  • Age
  • Hypogammaglobulinemia due to various conditions
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• Resolution for Missing/Weak Reacting Antibodies

  Enhancing reaction in reverse grouping by incubating patient’s serum with red cells at room temperature or specific temperatures
• Interpretation of Both Forward and Reverse Discrepancy
• Anomalous Results in ABO Testing
• Third Year 2nd Semester

  2023 – 2024
• Lecturer: 'MARILOU HONCULADA'
• Bachelor of Science in Medical Laboratory Science
• Gwyn Daphne Mancawan
• Causes of Unexpected Antigens

  • Autoantibody reactions
  • Naturally occurring anti-A1 in A2 and A2B individuals
  • Irregular antibodies from other blood group systems reacting with A or B cells
• Resolution for Unexpected Antigens


  1. Washing the patient's red cells in warm NSS

  2. Treating cells with chloroquine diphosphate

  3. Identifying the irregular antibody and using negative A and B cells
• Causes of Plasma Abnormalities

  • Increased gamma globulin levels
  • Abnormal proteins
  • Wharton’s Jelly in cord blood
• Resolution for Plasma Abnormalities

  Wash the patient’s cells with saline or add a drop of saline to remove proteins causing rouleaux