Based on the serology results (anti-A 0, anti-B 2+ mf, plasma A1 cells 4+, plasma B cells 0), what is the interpretation?

Based on the serology results (anti-A 0, anti-B 2+ mf, plasma A1 cells 4+, plasma B cells 0), what is the interpretation?

• A. Subgroup of A
• B. Polyagglutination
• C. Bx
• D. Unwashed cells

Answer: (C)

This pattern points to a rare B variant called Bx. The B antigen is present but expressed inconsistently on red cells, so anti-B shows a mixed-field or weaker reaction rather than a normal strong B reaction. At the same time, anti-A is not involved, which fits with a B-type variant rather than an A subgroup. The discordant results between forward (cell) and reverse (plasma) typing—strong or mixed-field reactions with B-related testing while A-related testing is absent—are characteristic of Bx. This is not explained by a subgroup of A (would center on A antigen/anti-A patterns), nor by polyagglutination (would produce widespread, non-specific reactivity across many cell types), nor by unwashed cells (that artifact yields non-specific background agglutination rather than a clean, B-focused pattern).

This pattern points to a rare B variant called Bx. The B antigen is present but expressed inconsistently on red cells, so anti-B shows a mixed-field or weaker reaction rather than a normal strong B reaction. At the same time, anti-A is not involved, which fits with a B-type variant rather than an A subgroup. The discordant results between forward (cell) and reverse (plasma) typing—strong or mixed-field reactions with B-related testing while A-related testing is absent—are characteristic of Bx.

This is not explained by a subgroup of A (would center on A antigen/anti-A patterns), nor by polyagglutination (would produce widespread, non-specific reactivity across many cell types), nor by unwashed cells (that artifact yields non-specific background agglutination rather than a clean, B-focused pattern).