Which statement is not true of weak D antigens?

Which statement is not true of weak D antigens?

• A. They must be incubated at 4 degrees C
• B. They are detected by all standard serologic methods
• C. They react best at room temperature
• D. They are variants of the D antigen

Answer: (A)

Weak D antigens are low-density forms of the D antigen on red cells. Because the D antigen is expressed weakly, you need enhanced serologic testing—typically an indirect antiglobulin test (IAT) with anti-D—to reveal them, using either room temperature or 37°C incubation with the AHG step. Incubation at 4°C is not a required or standard part of weak D testing; 4°C is associated with certain cold-reactive antibodies, not with detecting weak D. Therefore, the statement about needing 4°C incubation is not true. Weak D represents variants of the D antigen, and with appropriate testing, they can be demonstrated without cold incubation.

Weak D antigens are low-density forms of the D antigen on red cells. Because the D antigen is expressed weakly, you need enhanced serologic testing—typically an indirect antiglobulin test (IAT) with anti-D—to reveal them, using either room temperature or 37°C incubation with the AHG step. Incubation at 4°C is not a required or standard part of weak D testing; 4°C is associated with certain cold-reactive antibodies, not with detecting weak D. Therefore, the statement about needing 4°C incubation is not true. Weak D represents variants of the D antigen, and with appropriate testing, they can be demonstrated without cold incubation.