All of the following statements concerning the washing of cells are true except which one?

• A. Red blood cells must be resuspended in saline before adding AHG reagent
• B. Red blood cells must be washed thoroughly to remove serum proteins
• C. Red blood cells should be washed quickly to avoid antibody neutralization
• D. Washing steps remove residual serum and unbound antibodies

Answer: (C)

Washing red blood cells before the antiglobulin (AHG) step is all about removing everything free in the plasma—serum proteins and unbound antibodies—so that only antibodies bound to the red cells remain for detection by AHG. This makes the test specific for true cell-bound IgG or complement.

The steps are typically gentle but thorough: resuspend the cell pellet in isotonic saline, centrifuge to pellet, discard the supernatant, and repeat several times (usually 3–4 washes). After the final wash, the cells are resuspended in a small volume of saline before adding AHG. This ensures unbound components are cleared and minimizes interference.

Resuspending in saline before AHG is standard, and thorough washing to remove serum proteins and unbound antibodies is essential, so those statements are true. Washing quickly to avoid antibody neutralization isn’t a valid concern—there’s no antibody “neutralization” that washing prevents; bound antibodies remain on the cell, and too-rapid washing isn’t the reason to wash. If washed too aggressively or too many times, you can risk losing some bound antibodies or damaging cells, but normal practice emphasizes proper, gentle, thorough washing rather than speed. Therefore, the exception is the statement about washing quickly to avoid antibody neutralization.