ABO Typing Discrepancies

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Author: Candice Freeman, MLS(ASCP)BBCM, CQA(ASQ)
Reviewer: Barbara Cebulski, MS, MLS(ASCP)CM

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Continuing Education Credits

  • P.A.C.E.® Contact Hours: 2 hour(s)
  • Florida Board of Clinical Laboratory Science CE - General (Blood Banking / Immunohematology): 2 hour(s)


  • Demonstrate knowledge and understanding of ABO testing and result interpretation.
  • Identify the types of ABO discrepancies and explain the impact that discrepancies can have upon patient care and patient safety.
  • Accurately and efficiently detect an ABO discrepancy and apply serological techniques to resolve the error to ensure the correct ABO type is reported.
  • Discuss how different test methodologies, including tube, column agglutination, and solid phase, produce varying results with regard to discrepant ABO types.
  • Analyze preanalytical, analytical, and postanalytical steps to uncover a potential ABO discrepancy.

Course Outline

  • Introduction
      • Course Overview
  • Basics of Immunology and ABO Testing
    • Immunology Principles
      • Antigen/Antibody Interaction
      • Antigens and Antibodies
      • Affinity and Avidity
      • Zeta Potential and van der Waals Forces
      • Agglutination
      • Agglutination Chart
      • Antigens and antibodies specifically combine to form immune complexes. What term refers to the antibody's attraction to a particular antigenic determi...
      • Drag and drop the explanation, description, or definition to its correct immunology term.
    • ABO Testing
      • ABO Groups and Frequencies
      • ABO Testing and Interpretation
      • Review the following test results and match the expected reaction pattern to the reported ABO type.
  • ABO Typing Discrepancies
      • ABO Typing Discrepancies
      • Classifying ABO Discrepancies
      • ABO Discrepancies Related to Subgroups of A or B
      • Weakened or Missing Reactions in the Reverse Typing
      • Acquired B Phenomenon
      • Plasma Protein-Related Discrepancies
      • Miscellaneous Causes of ABO Discrepancies
      • A patient's pretransfusion ABO grouping results are as follows:Forward (Cell) GroupingReverse (Serum) GroupingAnti-AAnti-BAnti-A,BA1 CellsB Cells4+04+...
  • Resolution Strategies
      • Preanalytical Considerations
      • ABO Discrepancy Resolution: General Guidelines
      • Reagents and Techniques/Testing Methods Used in ABO Discrepancy Resolution
      • Example: Weak/Missing Reaction in the Forward Typing
      • Example: Weak/Missing Reaction in the Reverse Typing
      • Incubate at Room Temperature or In the Refrigerator
      • Example: Unexpected Reaction in Forward Typing
      • Example: Unexpected Reaction in Reverse Typing
      • Reverse Typing Discrepancies: Identify the Unexpected Antibody
      • Auto Control and O Cell Control
      • Testing with Lectins
      • In Addition To... Not a Replacement Of...
      • Concurrent Result Documentation to Prevent Errors
  • Comparison of Testing Methodologies
      • ABO Testing Methodologies
      • Stepping Back to Resolve an ABO Discrepancy
  • Case Studies: Resolving Discrepancies on the Bench
      • Case Study Review and Performance
      • Case Study 1An 83-year-old female is undergoing pre-op testing which includes a type and screen with a 2-unit Red Cell crossmatch. One 7mL EDTA tube w...
      • Case Study 2A 38 year old female patient has a history of chronic anemia which has resulted in 4 previous allogenic packed red blood cell transfusions...
      • Case Study 3 A 36 year old man has a history of gastrointestinal conditions including Crohn's Disease. He has been admitted to the hospital for a gene...
      • Case Study 4 A 44 year old woman has a history of Rheumatoid arthritis and chronic anemia, historically treated with diet and iron supplements. She ha...
      • Case Study 5 A 48-year-old woman has been hospitalized with an infection of Mycoplasma pneumoniae. At the patient's request, her physician has ordered...
  • References
      • References

Additional Information

Level of instruction: Intermediate

Intended Audience: Medical laboratory scientists, medical technologists, and technicians. This course is also appropriate for medical laboratory science students and pathology residents.
Author information: Candice Freeman, MLS(ASCP)BBCM, CQA(ASQ) is an instructor in the Medical Laboratory Technology Program at Sandhills Community College, Pinehurst, NC. She has many years of clinical laboratory experience, mainly as a blood bank and microbiology technologist. She has also held the position of Laboratory Manager/Laboratory Administrator. Candice holds a BS degree in Clinical Laboratory Science from Winston-Salem State University and is completing a Master’s program in Education in New Media and Global Education, Instructional Design Specialist.
Reviewer information: Barbara Cebulski, MS, MLS(ASCP)<sup>CM</sup> has recently retired as a Program Director for MediaLab, Inc., located in Lawrenceville, GA. She has over 30 years experience in the medical laboratory profession as a technologist, section supervisor, and laboratory manager. She also was employed for nine years by the College of American Pathologists in the Laboratory Accreditation Program. Barbara holds a Masters in Instructional Technology from Georgia State University. 

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