An antibody screen gave no reactions at immediate spin or 37C, but showed a 2+ reaction when AHG was added. The most likely antibody causing these results would be

An antibody screen gave no reactions at immediate spin or 37C, but showed a 2+ reaction when AHG was added. The most likely antibody causing these results would be

• A. Anti-Jka
• B. Anti-Fya
• C. Anti-K
• D. Anti-D

Answer: (A)

The key idea is that an antibody that shows reactivity only in the antiglobulin (AHG) phase indicates an IgG alloantibody that binds red cells but isn’t detected by immediate spin or at 37°C. AHG detects IgG already bound to the RBC surface by bridging through the antihuman globulin, so these antibodies often appear negative in IS and at 37°C and become clearly positive when AHG is used. Among the options, anti-Jka from the Kidd system is the classic example of this pattern. Kidd antibodies often have low affinity and can be weak at immediate spin and at 37°C, but they are reliably detected with AHG, producing a strong positive reaction. This pattern makes anti-Jka the best fit for a screen that’s negative at IS and 37°C but positive with AHG. Anti-D, anti-K, and anti-Fya can be AHG-positive as well, but they more commonly show reactivity at IS, at 37°C, or both, and are not as characteristically negative in IS/37°C and positive only with AHG as anti-Jka tends to be.

The key idea is that an antibody that shows reactivity only in the antiglobulin (AHG) phase indicates an IgG alloantibody that binds red cells but isn’t detected by immediate spin or at 37°C. AHG detects IgG already bound to the RBC surface by bridging through the antihuman globulin, so these antibodies often appear negative in IS and at 37°C and become clearly positive when AHG is used.

Among the options, anti-Jka from the Kidd system is the classic example of this pattern. Kidd antibodies often have low affinity and can be weak at immediate spin and at 37°C, but they are reliably detected with AHG, producing a strong positive reaction. This pattern makes anti-Jka the best fit for a screen that’s negative at IS and 37°C but positive with AHG.

Anti-D, anti-K, and anti-Fya can be AHG-positive as well, but they more commonly show reactivity at IS, at 37°C, or both, and are not as characteristically negative in IS/37°C and positive only with AHG as anti-Jka tends to be.