Which reagents are routinely used in forward grouping?

• A. Anti-A only
• B. Anti-B only
• C. Anti-A and Anti-B
• D. Anti-A and Anti-B in a single vial

Answer: (C)

Forward grouping works by exposing the red cells to antisera that specifically bind A and B antigens to see which antigens are present on the cell surface. To confidently determine a person’s ABO type, you need reagents that can detect both A and B antigens. Using only one antisera would reveal only one antigen and could miss the other, leading to misclassification (for example, AB could be mistaken for A, or O could be misread). When both anti-A and anti-B are used, the pattern of agglutination across the two tests clearly indicates A, B, AB, or O. In practice, these reagents are used together (often in a combined vial or as separate tests), making Anti-A and Anti-B the routine choice for forward grouping.