ABO Typing Discrepancies (by LabCE)

1.5 P.A.C.E. contact hour(s)

(based on 1,321 customer ratings)

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

Course provided by LabCE.

Discrepancies in ABO typing lead to delays in determination of products that are safe to transfuse to the patient. When the ABO type has not clearly been determined, transfusion of universal donor red cells and plasma are necessary, thus depleting the supply of these products. It is important to know the possible causes of ABO discrepancies in order to develop algorithms and standard procedures to resolve them quickly. This course will provide a general scheme for resolving ABO discrepancies and work through examples cases.

See more courses in: Blood Banking / Immunohematology

Continuing Education Credits

P.A.C.E.® Contact Hours (acceptable for AMT, ASCP, and state recertification): 1.5 hour(s)
Course number 578-038-21, approved through 6/30/2023
Florida Board of Clinical Laboratory Personnel Credit Hours - General (Blood Banking / Immunohematology): 1.5 hour(s)
Course number 20-869596, approved through 6/30/2023


  • 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.

Customer Ratings

(based on 1,321 customer ratings)

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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
    • ABO Testing
      • ABO Groups and Frequencies
      • ABO Testing and Interpretation
  • 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
  • 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
  • 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, medical laboratory technician 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)CM 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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Course provided by LabCE.
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