Inadequate washing of cord red blood cells may result in which outcome?

• A. False positive due to Wharton's jelly contamination
• B. False negative due to insufficient washing
• C. Hemolyzed sample causing isohemagglutination
• D. No reaction due to wash solution

Answer: (A)

Washing cord blood red cells is done to remove plasma proteins and contaminants that can cause non-specific reactions. Cord samples can be contaminated with Wharton’s jelly, a gelatinous tissue from the umbilical cord. If washing is inadequate, remnants of this jelly can stay with the red cells and promote nonspecific agglutination or other artifacts during serologic testing. That interference can produce a false-positive result even when there isn’t a true antibody or antigen reaction. The other scenarios—false negatives from insufficient washing, a hemolyzed sample causing unusual agglutination, or a wash solution preventing any reaction—don’t fit the typical artifact caused by residual Wharton’s jelly, which more commonly yields spurious positive findings.