Introduction to the ABO Blood Group System (Online CE Course)

(based on 1,393 customer ratings)

Catherine E. Newkirk, MS, MT(ASCP), Janet H. Coggins, MT(ASCP), SBB
Reviewers: Aileen Hyde MS, MT(ASCP), Paul Fekete, MD

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 154 CE courses, most popular
$95Add to cart
Pick Your Courses
Up to 8 CE hours
$50Add to cart
Individual course$20Add to cart
Need multiple seats for your university or lab? Get a quote

Introduction to ABO Blood Group System is an introductory-level course appropriate for MT and MLT students, pathology residents, or others who need a review of basic biochemistry, genetics, and reactions of the ABO system.

This course can also be used for CLS schools for academic instruction or could be used as a basic orientation for MT and MLT students who are beginning their blood bank rotation during internship.

See all available courses

Continuing Education Credits

P.A.C.E.® Contact Hours (acceptable for AMT, ASCP, and state recertification): 1 hour(s)
Approved through 8/31/2022
Florida Board of Clinical Laboratory Personnel Credit Hours - General (Blood Banking / Immunohematology): 1 hour(s)
Approved through 9/1/2022


  • Outline the background and development of the ABO system.
  • List antigens and antibodies of the system, including A subgroups.
  • Discuss the inheritance of the ABO antigens, including explanations of genotypes and phenotypes.
  • Discuss development of serum antibodies with respect to "naturally" occurring antibodies and immune antibodies.
  • Explain the procedure for routine ABO slide and tube typing and interpretation of results.
  • Determine the ABO blood group, given the forward and reverse typing results.

Customer Ratings

(based on 1,393 customer ratings)

Course Outline

Click on the links below to preview selected pages from this course.
  • Background and Introduction to the ABO System
      • Importance of Understanding the ABO System
      • The History of the ABO System
      • The History of the ABO System, continued
      • Table 1: ABO Blood Group System
      • Table 2: Testing the Patient Red Cells with Known Antisera (Forward Typing)
      • Table 3: Testing the Serum with Known Red Cells (Reverse Typing)
      • Why does agglutination (clumping) sometimes occur when red blood cells (RBCs) from one individual are mixed with serum from another?
      • Match the blood types in the drop-down boxes with the characteristics on the right.
      • To determine the ABO type, known antisera are mixed with patient RBCs, and known red cells are mixed with patient serum.
  • Development of Serum Antibodies
      • ABO Antibodies
      • Anti-A and Anti-B Development
      • ABO Antibodies and Aging
      • Immune ABO Antibodies
      • Immunoglobulin
      • Which of the following are examples of events that may produce immune ABO antibodies?
      • Which of the following is the predominant immunoglobulin class for anti-A and anti-B antibodies?
  • Subgroups of A
      • Strength of the A Antigen
      • A1 and A2 Subgroups
      • Rare Subgroups of A
      • Inherited Antigens
      • Why Knowledge of A Subgroups Is Important For Laboratory Professionals
      • Reaction of Red Cell Subgroups With Known Antisera
      • A1 and A2 individuals cannot be differentiated.
      • Given the results below, what is the most probable ABO type for this individual?Forward (Cell) Grouping Reverse (Serum) Grouping Anti-AAnti-BAnti-A,BA...
      • The serum of some group A individuals may agglutinate group A1 cells.
  • ABO Typing
      • Agglutination Reactions
      • Forward Typing
      • Testing the Red Cells With Known Antisera
      • Reverse Typing
      • Testing Patient Serum With Known Reagent Red Cells (Reverse Grouping)
      • Interpretation of ABO Group
      • Example of an ABO discrepancy
      • Automated Systems
      • At what temperature range is the ABO antigen-antibody reaction best observed?
      • Match the blood types from the drop-down boxes with the appropriate descriptions to the right of the boxes.
  • Genetic Basis for Cellular Antigens
      • Galactose and ABO Antigen Precursor Substance
      • Fucose
      • "A" Antigenic Activity
      • "B" Antigenic Activity
      • The H gene
      • The Bombay Blood Group
      • A, B, and O Genes
      • A, B, and O Genes - Diagram
      • Bombay Blood Group Genes
      • Inherited Genes
      • Deducing the Gene
      • Genotyping
      • Determining Possible Offspring
      • Punnett Squares
      • Which specific terminal sugar causes a red cell to have A antigenic activity?
      • Which specific terminal sugar causes a red cell to have B antigenic activity?
      • What specific sugar configuration is necessary as a base for attachment of other sugars?
      • Which of the following phenotypes is NOT possible in an offspring from an AB and BO mating?
      • What is present in the blood of an individual with the Bombay phenotype which will cause it to agglutinate with any non-Bombay individual's blood?
      • Use the drop-down boxes to match the blood types (phenotypes) that will be expressed with the genotypes listed to the right of the boxes.
  • References

Additional Information

Level of Instruction: Intermediate
Intended Audience: Medical Laboratory Scientists (MLS), Medical Laboratory Technicians (MLT) and Medical Laboratory Science students who wish to review basic principles of the ABO blood group system.
About this Course: This course is part of a series of courses adapted for the web by MediaLab Inc. under license from Educational Materials for Health Professionals Inc. Dayton OH, 45420. Copyright EMHP Inc. The course was most recently reviewed and revised in 2018.
Course Description: This course explains the basic genetics and principles of the ABO blood group system, as well as the tube methods for forward and reverse ABO grouping. Learners will benefit most from this course if they already possess a basic understanding of genetic principles, immune response, the production and structure of antibodies, and antigen-antibody reactions.

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 154 CE courses, most popular
$95Add to cart
Pick Your Courses
Up to 8 CE hours
$50Add to cart
Individual course$20Add to cart
Need multiple seats for your university or lab? Get a quote
Gel Card Reaction Grading (2)

Bombay genes