ABO Blood Group Testing System
The correct answer is C) Compatibility test system, which encompasses the hemagglutination-based serological methods (tube testing and gel agglutination) used to determine ABO blood groups through antigen-antibody reactions.
Core Testing Methodology
ABO blood group determination relies on compatibility testing systems that detect hemagglutination reactions between red blood cell antigens and specific antibodies 1, 2. This is fundamentally different from coagulation tests, urine strips, or pregnancy tests.
Standard Serological Methods
The two primary clinical approaches are:
- Hemagglutination tube test: The traditional method where red cells are mixed with anti-A and anti-B antibodies to observe agglutination patterns 3, 2
- Microcolumn gel test: An FDA-approved alternative that uses gel cards to detect agglutination, performing equivalently to tube testing for ABO grouping 4, 3
Both methods function as compatibility test systems by examining the interaction between antigens on red blood cells and corresponding antibodies 1.
Forward and Reverse Typing Components
ABO typing requires a dual compatibility testing approach to ensure accuracy 2:
- Forward typing (cell typing): Tests patient red cells against known anti-A and anti-B antibodies to identify which antigens are present 2
- Reverse typing (serum typing): Tests patient serum/plasma against known A and B red cells to detect expected isoagglutinins, confirming the forward typing results 2
This bidirectional compatibility testing distinguishes ABO determination from simple single-direction assays 2.
Why Other Options Are Incorrect
Coagulation test systems measure clotting factors and platelet function—completely unrelated to blood group antigen detection 1. Urine test strips detect urinary metabolites and have no role in red cell antigen identification. Pregnancy tests detect hCG hormone and are irrelevant to blood banking 1.
Clinical Significance of the Compatibility System
The compatibility test system approach is critical because ABO incompatibility remains the most clinically significant cause of fatal transfusion reactions 3, 1. The crossmatch—the final compatibility test before transfusion—examines donor-recipient compatibility by testing for reactions between donor cells and recipient antibodies 1, 2.
Emerging Technologies
While genotyping methods are increasingly used for complex cases and variant antigen identification, serological compatibility testing remains the routine clinical standard 3, 1, 5. Molecular methods supplement but do not replace hemagglutination-based compatibility testing for standard ABO determination 1, 5.