Reverse Grouping (Serum Grouping)
Definition
Testing a person's serum against known A1 and B reagent red cells to identify which antibodies are present. A healthy adult with group A blood will have anti-B in their serum. Reverse grouping validates the forward result and detects discrepancies.
- Field
- Forensic blood grouping
- Tests
- Serum against known A1 and B reagent cells
- Detects
- Naturally occurring anti-A and anti-B antibodies
- Purpose
- Cross-checks the forward (cell) grouping result
Common questions
Why is reverse grouping needed if forward grouping already gives the ABO type?+
Forward and reverse grouping should agree by Landsteiner's rule since the antibodies present are those against antigens absent from the person's own cells. A mismatch between the two flags a subgroup, technical error, or unusual serology needing further work before reporting a result.
Can reverse grouping be performed on old or degraded bloodstains?+
Reverse grouping depends on intact, reactive antibody protein, which degrades faster than cell-surface antigens, so it is far less reliable on aged forensic bloodstains than forward antigen typing and is rarely the primary method on casework stains.
What does a discrepancy between forward and reverse grouping usually indicate?+
Common causes include weak or missing expected antibodies in infants or immunocompromised individuals, ABO subgroups such as A2, technical errors, or unexpected alloantibodies, each requiring resolution before a definitive group is assigned.
Related terms
- ABO Transferase
- A glycosyltransferase enzyme encoded by the ABO gene on chromosome 9. The A allele encodes an enzyme that adds N-acetylgalactosamine to H...
- Bombay Phenotype (Oh)
- A rare phenotype in which individuals lack functional H antigen on red cells and in secretions due to mutations in FUT1 (and...
- Forward Grouping (Cell Grouping)
- The direct test of red blood cells with known anti-A and anti-B reagent antibodies to determine which ABO antigens are present on...
- H Antigen
- A fucose-containing oligosaccharide on red cell surfaces and secreted epithelial cells, produced by FUT1 (on red cells) and FUT2 (in secretions). It...
- Secretor Status
- A genetic trait that determines whether a person expresses their ABO blood group antigens in secreted body fluids such as saliva, semen,...