During daily quality control of the AHG reagent, which red blood cells are used and what is the expected result?

• A. Group A check cells plus AHG yields a strong positive reaction
• B. Group O check cells plus AHG yields a weak positive reaction
• C. Group B check cells plus AHG yields negative
• D. Group AB check cells plus AHG yields no reaction

Answer: (B)

The test concept here is validating that the antihuman globulin (AHG) reagent is active by using a known positive control. For daily QC of AHG, you use red blood cells that are prepared as check cells and are Group O so they won’t introduce ABO-specific reactions. These check cells are set up so there is a small, controlled amount of IgG coating available, which the AHG reagent can bridge to produce visible agglutination.

The expected result is a weak positive reaction. This shows the AHG reagent is functioning properly without being overly strong (which could indicate too much IgG coating or an overly potent reagent) or completely negative (which would suggest the reagent is degraded). So Group O check cells plus AHG yielding a weak positive is the correct, anticipated QC outcome.